Kalle Rosenbaum [ARCHIVE]

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🗓️ Active from 2015-03-13 to 2023-05-11
💬 Posted a total of 44 messages
📚 Participated in the following categories: Bitcoin-development, bitcoin-dev, RFC, BIP Proposal
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npub1uwweecasakwtk96j3vjmkjenhnhyv4rku382txq0kmexjwuh4w2st55zf7

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nprofile1qqsw88vuuwcwm89mzafgkfdmfvememjx23mwgn49nq8mdunf8wt6h9gm0pl0n

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npub1uwweecasakwtk96j3vjmkjenhnhyv4rku382txq0kmexjwuh4w2st55zf7

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Last Notes

2023-06-07 23:21:39

- reply

📅 Original date posted:2023-05-11
🗒️ Summary of this message: Paying high fees in Bitcoin can incentivize honest mining during state-level censorship attacks. Multiple transactions can be used to bypass fee limits.
📝 Original message:Another use case for paying more fees than outputs is to incentivize
honest mining when Bitcoin is under a state-level censorship attack.
If it's really important to me that my transaction goes through, I
might be willing to set a fee at 99x the output value. It's the only
way bitcoin could work in an adversarial environment.
/Kalle
On Thu, 11 May 2023 at 13:55, vjudeu via bitcoin-dev
<bitcoin-dev at lists.linuxfoundation.org> wrote:
>
> > confused. the rule was "cannot pay a fee > sum of outputs with consideration of cpfp in the mempool"
> > your example is of someone paying a fee "< sum" which wouldn't be blocked
>
> Every transaction paying "fee > sum" can be replaced by N transactions paying "fee <= sum", where the sum of all fees will be the same. That means, someone will still do the same thing, but it will be just expanded into N transactions, so you will reach the same outcome, but splitted into more transactions. That means, mempool will be even more congested, because for example instead of 1kB transaction with huge fee, you will see 100 such transactions with smaller fees, that will add to the same amount, but will just consume more space.
>
> > show me how someone could move 1 btc and pay 2 btc as fees...
>
> In the previous example, I explained how someone could move 1k sats and pay almost 1 BTC as fees. But again, assuming that you have 3 BTC, and you move 1 BTC with 2 BTC fee, that will be rejected by your rules if and only if that will be done in a single transaction. But hey, the same owner can prepare N transactions upfront, and release them all at the same time, Segwit makes it possible without worrying about malleability.
>
> So, instead of:
>
> 3 BTC -> 1 BTC
>
> You can see this:
>
> 3 BTC -> 2 BTC -> 1 BTC
>
> If that second transaction will not pass CPFP, more outputs could be used:
>
> +--------------------+--------------------+--------------------+
> | 3.0 BTC -> 0.5 BTC | 0.5 BTC -> 0.5 BTC | 0.5 BTC -> 0.5 BTC |
> | 0.5 BTC | 0.5 BTC 0.5 BTC | 0.5 BTC |
> | 0.5 BTC | 0.5 BTC +--------------------+
> | +--------------------+
> | 0.5 BTC | 0.5 BTC -> 0.5 BTC |
> | 0.5 BTC | 0.5 BTC |
> +--------------------+--------------------+
>
> As you can see, there are four transactions, each paying 0.5 BTC fee, so the total fee is 2 BTC. However, even if you count it as CPFP, you will get 1.5 BTC in fees for the third transaction in the chain. Note that more outputs could be used, or they could be wired a bit differently, and then if you will look at the last transaction, the sum of all fees from 10 or 15 transactions in that chain, could still pass your limits, but the whole tree will exceed that. If you have 1.5 BTC limit for that 3 BTC, then you could have 20 separate chains of transactions, each paying 0.1 BTC in fees, and it will still sum up to 2 BTC.
>
> > the only way around it is to maintain balances and use change addresses. which would force nft and timestamp users to maintain these balances and would be a deterrent
>
> Not really, because you can prepare all of those transactions upfront, as the part of your protocol, and release all of them at once. You don't have to maintain all UTXOs in between, you can create the whole transaction tree first, sign it, and broadcast everything at once. More than that: if you have HD wallet, you only need to store a single key, and generate all addresses in-between on-the-fly, as needed. Or even use some algorithm to deterministically recreate the whole transaction tree.
>
>
>
> On 2023-05-10 19:42:49 user Erik Aronesty <erik at q32.com> wrote:
> confused. the rule was "cannot pay a fee > sum of outputs with consideration of cpfp in the mempool"
>
>
> your example is of someone paying a fee "< sum" which wouldn't be blocked
>
>
> note: again, i'm not a fan of this, i like the discussion of "bitcoin as money only" and using fee as a lever to do that
>
>
> show me how someone could move 1 btc and pay 2 btc as fees... i think we can block it at the network or even the consensus layer, and leave anything but "non-monetary use cases" intact. the only way around it is to maintain balances and use change addresses. which would force nft and timestamp users to maintain these balances and would be a deterrent
>
>
> im am much more in favor of doing something like op_ctv which allows many users to pool fees and essentially "share" a single utxo.
> .
>
>
>
> On Wed, May 10, 2023 at 12:19 PM <vjudeu at gazeta.pl> wrote:
>
> > possible to change tx "max fee" to output amounts?
>
> Is it possible? Yes. Should we do that? My first thought was "maybe", but after thinking more about it, I would say "no", here is why:
>
> Starting point: 1 BTC on some output.
> Current situation: A single transaction moving 0.99999000 BTC as fees, and creating 1000 satoshis as some output (I know, allowed dust values are lower and depend on address type, but let's say it is 1k sats to make things simpler).
>
> And then, there is a room for other solutions, for example your rule, mentioned in other posts, like this one: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2023-May/021626.html
>
> > probably easier just to reject any transaction where the fee is higher than the sum of the outputs
>
> Possible situation after introducing your proposal, step-by-step:
>
> 1) Someone wants to move 1 BTC, and someone wants to pay 0.99999000 BTC as fees. Assuming your rules are on consensus level, the first transaction creates 0.5 BTC output and 0.5 BTC fee.
> 2) That person still wants to move 0.5 remaining BTC, and still is willing to pay 0.49999000 BTC as fees. Guess what will happen: you will see another transaction, creating 0.25 BTC output, and paying 0.25 BTC fee.
> ...
> N) Your proposal replaced one transaction, consuming maybe one kilobyte, with a lot of transactions, doing exactly the same, but where fees are distributed between many transactions.
>
> Before thinking about improving that system, consider one simple thing: is it possible to avoid "max fee rule", no matter in what way it will be defined? Because as shown above, the answer seems to be "yes", because you can always replace a single transaction moving 1 BTC as fees with multiple transactions, each paying one satoshi per virtual byte, and then instead of consuming around one kilobyte, it would consume around 1 MvB per 0.01 BTC, so 100 MvB per 1 BTC mentioned in the example above.
>
>
>
> On 2023-05-08 13:55:18 user Erik Aronesty via bitcoin-dev <bitcoin-dev at lists.linuxfoundation.org> wrote:
> possible to change tx "max fee" to output amounts?
>
>
> seems like the only use case that would support such a tx is spam/dos type stuff that satoshi warned about
>
>
> its not a fix for everything, but it seems could help a bit with certain attacks
>
>
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev

2023-06-07 18:14:58

- reply

📅 Original date posted:2018-10-08
📝 Original message:Hi Велеслав,
I won't comment on the usability of/need for this system, but I have a few
random comments and questions:
Why demand exactly one input? This will probably cause problems for wallets
with many small value UTXOs and no big.
Why demand exactly type p2wpkh on input? Why limit at all?
32-byte-nym_public_key is actually 33 bytes, no? Compressed pubkeys are 33
bytes.
Why verify "SIZE 32 EQUALVERIFY" on output 2? It puts a ceiling on the
entropy, but no floor, so it seems useless.
Why require segwit version 0 change output? This seems like an unnecessary
limitation.
It's not clear to me what's IsStandard rules and what's nym protocol rules
in the specification section. I interpret the specification to specify
IsStandard rules, but the section also mentions stuff not relevant to that,
for example how the nym signature is constructed and what the opreturn data
consists of. You should make the distinction more clear.
I couldn't find info on what 1-byte-nym_version and 1-byte-nym_use are and
how they are used. But it might not belong in the BIP if it only should
describe IsStandard policies?
Regards,
Kalle
Sent from my Sinclair ZX81
Den sön 7 okt. 2018 05:57Велеслав via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> skrev:
> Hello list,
>
> I would like to propose a draft BIP that takes the next available
> transaction version number and defines a new transaction template. This
> proposal does not have any consensus changes, and is purely for the
> application layer of Bitcoin. The new transaction template defines a
> special transaction structure that can be used as a cryptographic pseudonym.
>
> I hope the community will find this proposal useful and will find time to
> give it careful review.
>
> Here is the first BIP within our project
> https://github.com/veleslavs/bips/blob/bip_nym_tx/bip-nym_tx.mediawiki
>
> I would like to thank the entire team that has supported me in creating
> this proposal.
>
> С наилучшими пожеланиями,
> Велеслав
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
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2023-06-07 18:11:12

- reply

📅 Original date posted:2018-03-14
📝 Original message:Thank you.
I can't really see from your proposal if you had thought of this: A soft
fork can make old nodes accept invalid message signatures as valid. For
example, a "signer" can use a witness version unknown to the verifier to
fool the verifier. Witness version is detectable (just reject unknown
witness versions) but there may be more subtle changes. Segwit was not
"detectable" in that way, for example.
This is the reason why I withdrew BIP120. If you have thought about the
above, I'd be very interested.
/Kalle
Sent from my Sinclair ZX81
Den 14 mars 2018 16:10 skrev "Karl Johan Alm via bitcoin-dev" <
bitcoin-dev at lists.linuxfoundation.org>:
Hello,
I am considering writing a replacement for the message signing tools
that are currently broken for all but the legacy 1xx addresses. The
approach (suggested by Pieter Wuille) is to do a script based
approach. This does not seem to require a lot of effort for
implementing in Bitcoin Core*. Below is my proposal for this system:
A new structure SignatureProof is added, which is a simple scriptSig &
witnessProgram container that can be serialized. This is passed out
from/into the signer/verifier.
RPC commands:
sign <address> <message> [<prehashed>=false]
Generates a signature proof for <message> using the same method that
would be used to spend coins sent to <address>.**
verify <address> <message> <proof> [<prehashed>=false]
Deserializes and executes the proof using a custom signature checker
whose sighash is derived from <message>. Returns true if the check
succeeds, and false otherwise. The scriptPubKey is derived directly
from <address>.**
Feedback welcome.
-Kalle.
(*) Looks like you can simply use VerifyScript with a new signature
checker class. (h/t Nicolas Dorier)
(**) If <prehashed> is true, <message> is the sighash, otherwise
sighash=sha256d(message).
_______________________________________________
bitcoin-dev mailing list
bitcoin-dev at lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
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2023-06-07 18:10:17

- reply

📅 Original date posted:2018-01-26
📝 Original message:Hi
There is an inherent problem with BIP120, Proof of Payment: If there
is a soft fork, a server that verifies PoPs will accept a PoP as valid
without checking any of the new Bitcoin rules.
For example, a server will be fooled by a segwit transaction, because
the server doesn't have a witness to verify and consequently will
accept any PoP with an empty scriptSig.
Besides this problem, on-chain payments are not hot anymore and
interest, or need, for PoP as a concept seems low.
I have no good solution for the soft fork problem. Requiring all
software that uses PoP to upgrade to a new PoP specification on each
soft-fork is not good enough. Do you have any ideas on how to fix it?
If there is no good solution to the soft-fork issue, I suggest that I
withdraw BIP120 and BIP121.
As for current implementations: I know that Mycelium implements
BIP120, but I'm not sure if there is any other software, besides my
own, implementing it. If you know of any, please let me know so I can
discuss it with them.
Regards,
/Kalle

2023-06-07 18:08:50

- reply

📅 Original date posted:2017-12-18
📝 Original message:Hi Greg,
2017-12-18 21:42 GMT+01:00 Gregory Maxwell <greg at xiph.org>:
> Because it would make no meaningful difference now,
Sure.
> and if you are not
> going to check the history
I'm not going to do any less checks than a node running with assumevalid.
Well not exactly true, because a node running today with assumevalid will
verify the witness root hash, right?
> there are much more efficient things to
> do-- like not transfer it at all.
>
I'm not sure what you are referring to.
Thank you
/Kalle
>
> On Mon, Dec 18, 2017 at 8:32 AM, Kalle Rosenbaum via bitcoin-dev
> <bitcoin-dev at lists.linuxfoundation.org> wrote:
> > Dear list,
> >
> > I find it hard to understand why a full node that does initial block
> > download also must download witnesses if they are going to skip
> > verification anyway. If my full node skips signature verification for
> > blocks earlier than X, it seems the reasons for downloading the
> > witnesses for those blocks are:
> >
> > * to be able to send witnesses to other nodes.
> >
> > * to verify the witness root hash of the blocks
> >
> > I suppose that it's important to verify the witness root hash because
> > a bad peer may send me invalid witnesses during initial block
> > download, and if I don't verify that the witness root hash actually
> > commits to them, I will get banned by peers requesting the blocks from
> > me because I send them garbage.
> >
> > So both the reasons above (there may be more that I don't know about)
> > are actually the same reason: To be able to send witnesses to others
> > without getting banned.
> >
> > What if a node could chose not to download witnesses and thus chose to
> > send only witnessless blocks to peers. Let's call these nodes
> > witnessless nodes. Note that witnessless nodes are only witnessless
> > for blocks up to X. Everything after X is fully verified.
> >
> > Witnessless nodes would be able to sync faster because it needs to
> > download less data to calculate their UTXO set. They would therefore
> > more quickly be able to provide full service to SPV wallets and its
> > local wallets as well as serving blocks to other witnessless nodes
> > with same or higher assumevalid block. For witnessless nodes with
> > lower assumevalid they can serve at least some blocks. It could also
> > serve blocks to non-segwit nodes.
> >
> > Do witnessless nodes risk dividing the network in two parts, one
> > witnessless and one with full nodes, with few connections between the
> > parts?
> >
> > So basically, what are the reasons not to implement witnessless
> > nodes?
> >
> > Thank you,
> > /Kalle
> >
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev at lists.linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >
>
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2023-06-07 18:08:49

- reply

📅 Original date posted:2017-12-18
📝 Original message:Thanks Eric.
It would be a pity if early witnesses got lost due to nodes abandoning them
by running witnessless. But as long as there's at least one accessible
source for them left we're OKish. Let's hope we don't get to that point in
the near future. As long as Bitcoin Core doesn't implement witnessless
mode, there's little risk.
What do people here think about the benefits and risks with running
witnessless?
/Kalle
Sent from my Sinclair ZX81
Den 18 dec. 2017 17:19 skrev "Eric Voskuil" <eric at voskuil.org>:
> You can't know (assume) a block is valid unless you have previously
> validated the block yourself. But in the case where you have, and then
> intend to rely on it in a future sync, there is no need for witness data
> for blocks you are not going to validate. So you can just not request it.
>
> However you will not be able to provide those blocks to nodes that *are*
> validating; the client is pruned and therefore not a peer (cannot
> reciprocate). (An SPV client is similarly not a peer; it is a more deeply
> pruned client than the witnessless client.)
>
> There is no other reason that a node requires witness data. SPV clients
> don't need it as it is neither require it to verify header commitment to
> transactions nor to extract payment addresses from them.
>
> The harm to the network by pruning is that eventually it can become harder
> and even impossible for anyone to validate the chain. But because you are
> fully validating you individually remain secure, so there is no individual
> incentive working against this system harm.
>
> e
>
> On Dec 18, 2017, at 08:35, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>
> 2017-12-18 13:43 GMT+01:00 Eric Voskuil <eric at voskuil.org>:
>
>>
>> > On Dec 18, 2017, at 03:32, Kalle Rosenbaum via bitcoin-dev <
>> bitcoin-dev at lists.linuxfoundation.org> wrote:
>> >
>> > Dear list,
>> >
>> > I find it hard to understand why a full node that does initial block
>> > download also must download witnesses if they are going to skip
>> verification anyway.
>>
>> Why run a full node if you are not going to verify the chain?
>>
>
> I meant to say "I find it hard to understand why a full node that does
> initial block
> download also must download witnesses when it is going to skip
> verification of the witnesses anyway."
>
> I'm referring to the "assumevalid" feature of Bitcoin Core that skips
> signature verification up to block X. Or have I misunderstood assumevalid?
>
> /Kalle
>
>
>>
>> > If my full node skips signature verification for
>> > blocks earlier than X, it seems the reasons for downloading the
>> > witnesses for those blocks are:
>> >
>> > * to be able to send witnesses to other nodes.
>> >
>> > * to verify the witness root hash of the blocks
>> >
>> > I suppose that it's important to verify the witness root hash because
>> > a bad peer may send me invalid witnesses during initial block
>> > download, and if I don't verify that the witness root hash actually
>> > commits to them, I will get banned by peers requesting the blocks from
>> > me because I send them garbage.
>> > So both the reasons above (there may be more that I don't know about)
>> > are actually the same reason: To be able to send witnesses to others
>> > without getting banned.
>> >
>> > What if a node could chose not to download witnesses and thus chose to
>> > send only witnessless blocks to peers. Let's call these nodes
>> > witnessless nodes. Note that witnessless nodes are only witnessless
>> > for blocks up to X. Everything after X is fully verified.
>> >
>> > Witnessless nodes would be able to sync faster because it needs to
>> > download less data to calculate their UTXO set. They would therefore
>> > more quickly be able to provide full service to SPV wallets and its
>> > local wallets as well as serving blocks to other witnessless nodes
>> > with same or higher assumevalid block. For witnessless nodes with
>> > lower assumevalid they can serve at least some blocks. It could also
>> > serve blocks to non-segwit nodes.
>> >
>> > Do witnessless nodes risk dividing the network in two parts, one
>> > witnessless and one with full nodes, with few connections between the
>> > parts?
>> >
>> > So basically, what are the reasons not to implement witnessless
>> > nodes?
>> >
>> > Thank you,
>> > /Kalle
>> > _______________________________________________
>> > bitcoin-dev mailing list
>> > bitcoin-dev at lists.linuxfoundation.org
>> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>
>
>
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2023-06-07 18:08:48

- reply

📅 Original date posted:2017-12-18
📝 Original message:Hi Mark
Yes, it seems like sign-to-contract protocols, which I just now briefly
read about [1][2], may need to use historic witnesses. That raises the
question, what are Bitcoin witnesses for?
To me it seems witnesses should be regarded as temporary. But it seems both
respondents to this thread, Eric and Mark, mean that witnesses are forever.
I regard witnesses as a way to authenticate updates to the UTXO set, and
once buried deep enough in the blockchain, the witness is no longer needed,
because consensus has formed around the UTXO set update.
Suppose a transaction with an invalid witness happens to enter the
blockchain and gets buried 100000 blocks down with the witness still
available. Is the blockchain above it valid? I'd say the blockchain is
valid and that it was a bug that the transaction made it into the
blockchain. We will have to live with such bugs.
Another way to put it: Suppose that all witnesses from 2017 dissappears
from all nodes in 2020. Is the blockchain still valid? I think so. I would
continue using it without looking back.
With that approach, I think sign-to-contract protocols has to find ways to
work in a witnessless environment. For example, users of such protocols can
setup their own archival nodes.
I'd love to hear alternative views on this.
Thanks,
/Kalle
[1]
https://download.wpsoftware.net/bitcoin/wizardry/mw-slides/2017-03-mit-bitcoin-expo/slides.pdf
[2] https://bitcointalk.org/index.php?topic=893898.msg9861102#msg9861102
2017-12-18 18:30 GMT+01:00 Mark Friedenbach via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org>:
> Sign-to-contract enables some interesting protocols, none of which are in
> wide use as far as I’m aware. But if they were (and arguably this is an
> area that should be more developed), then SPV nodes validating these
> protocols will need access to witness data. If a node is performing IBD
> with assumevalid set to true, and is also intending to prune history, then
> there’s no reason to fetch those witnesses as far as I’m aware. But it
> would be a great disservice to the network for nodes intending to serve SPV
> clients to prune this portion of the block history.
>
>
> On Dec 18, 2017, at 8:19 AM, Eric Voskuil via bitcoin-dev <
> bitcoin-dev at lists.linuxfoundation.org> wrote:
>
> You can't know (assume) a block is valid unless you have previously
> validated the block yourself. But in the case where you have, and then
> intend to rely on it in a future sync, there is no need for witness data
> for blocks you are not going to validate. So you can just not request it.
>
> However you will not be able to provide those blocks to nodes that *are*
> validating; the client is pruned and therefore not a peer (cannot
> reciprocate). (An SPV client is similarly not a peer; it is a more deeply
> pruned client than the witnessless client.)
>
> There is no other reason that a node requires witness data. SPV clients
> don't need it as it is neither require it to verify header commitment to
> transactions nor to extract payment addresses from them.
>
> The harm to the network by pruning is that eventually it can become harder
> and even impossible for anyone to validate the chain. But because you are
> fully validating you individually remain secure, so there is no individual
> incentive working against this system harm.
>
> e
>
> On Dec 18, 2017, at 08:35, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>
> 2017-12-18 13:43 GMT+01:00 Eric Voskuil <eric at voskuil.org>:
>
>>
>> > On Dec 18, 2017, at 03:32, Kalle Rosenbaum via bitcoin-dev <
>> bitcoin-dev at lists.linuxfoundation.org> wrote:
>> >
>> > Dear list,
>> >
>> > I find it hard to understand why a full node that does initial block
>> > download also must download witnesses if they are going to skip
>> verification anyway.
>>
>> Why run a full node if you are not going to verify the chain?
>>
>
> I meant to say "I find it hard to understand why a full node that does
> initial block
> download also must download witnesses when it is going to skip
> verification of the witnesses anyway."
>
> I'm referring to the "assumevalid" feature of Bitcoin Core that skips
> signature verification up to block X. Or have I misunderstood assumevalid?
>
> /Kalle
>
>
>>
>> > If my full node skips signature verification for
>> > blocks earlier than X, it seems the reasons for downloading the
>> > witnesses for those blocks are:
>> >
>> > * to be able to send witnesses to other nodes.
>> >
>> > * to verify the witness root hash of the blocks
>> >
>> > I suppose that it's important to verify the witness root hash because
>> > a bad peer may send me invalid witnesses during initial block
>> > download, and if I don't verify that the witness root hash actually
>> > commits to them, I will get banned by peers requesting the blocks from
>> > me because I send them garbage.
>> > So both the reasons above (there may be more that I don't know about)
>> > are actually the same reason: To be able to send witnesses to others
>> > without getting banned.
>> >
>> > What if a node could chose not to download witnesses and thus chose to
>> > send only witnessless blocks to peers. Let's call these nodes
>> > witnessless nodes. Note that witnessless nodes are only witnessless
>> > for blocks up to X. Everything after X is fully verified.
>> >
>> > Witnessless nodes would be able to sync faster because it needs to
>> > download less data to calculate their UTXO set. They would therefore
>> > more quickly be able to provide full service to SPV wallets and its
>> > local wallets as well as serving blocks to other witnessless nodes
>> > with same or higher assumevalid block. For witnessless nodes with
>> > lower assumevalid they can serve at least some blocks. It could also
>> > serve blocks to non-segwit nodes.
>> >
>> > Do witnessless nodes risk dividing the network in two parts, one
>> > witnessless and one with full nodes, with few connections between the
>> > parts?
>> >
>> > So basically, what are the reasons not to implement witnessless
>> > nodes?
>> >
>> > Thank you,
>> > /Kalle
>> > _______________________________________________
>> > bitcoin-dev mailing list
>> > bitcoin-dev at lists.linuxfoundation.org
>> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
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2023-06-07 18:08:47

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📅 Original date posted:2017-12-18
📝 Original message:2017-12-18 13:43 GMT+01:00 Eric Voskuil <eric at voskuil.org>:
>
> > On Dec 18, 2017, at 03:32, Kalle Rosenbaum via bitcoin-dev <
> bitcoin-dev at lists.linuxfoundation.org> wrote:
> >
> > Dear list,
> >
> > I find it hard to understand why a full node that does initial block
> > download also must download witnesses if they are going to skip
> verification anyway.
>
> Why run a full node if you are not going to verify the chain?
>
I meant to say "I find it hard to understand why a full node that does
initial block
download also must download witnesses when it is going to skip verification
of the witnesses anyway."
I'm referring to the "assumevalid" feature of Bitcoin Core that skips
signature verification up to block X. Or have I misunderstood assumevalid?
/Kalle
>
> > If my full node skips signature verification for
> > blocks earlier than X, it seems the reasons for downloading the
> > witnesses for those blocks are:
> >
> > * to be able to send witnesses to other nodes.
> >
> > * to verify the witness root hash of the blocks
> >
> > I suppose that it's important to verify the witness root hash because
> > a bad peer may send me invalid witnesses during initial block
> > download, and if I don't verify that the witness root hash actually
> > commits to them, I will get banned by peers requesting the blocks from
> > me because I send them garbage.
> > So both the reasons above (there may be more that I don't know about)
> > are actually the same reason: To be able to send witnesses to others
> > without getting banned.
> >
> > What if a node could chose not to download witnesses and thus chose to
> > send only witnessless blocks to peers. Let's call these nodes
> > witnessless nodes. Note that witnessless nodes are only witnessless
> > for blocks up to X. Everything after X is fully verified.
> >
> > Witnessless nodes would be able to sync faster because it needs to
> > download less data to calculate their UTXO set. They would therefore
> > more quickly be able to provide full service to SPV wallets and its
> > local wallets as well as serving blocks to other witnessless nodes
> > with same or higher assumevalid block. For witnessless nodes with
> > lower assumevalid they can serve at least some blocks. It could also
> > serve blocks to non-segwit nodes.
> >
> > Do witnessless nodes risk dividing the network in two parts, one
> > witnessless and one with full nodes, with few connections between the
> > parts?
> >
> > So basically, what are the reasons not to implement witnessless
> > nodes?
> >
> > Thank you,
> > /Kalle
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev at lists.linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
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2023-06-07 18:08:46

- reply

📅 Original date posted:2017-12-18
📝 Original message:Dear list,
I find it hard to understand why a full node that does initial block
download also must download witnesses if they are going to skip
verification anyway. If my full node skips signature verification for
blocks earlier than X, it seems the reasons for downloading the
witnesses for those blocks are:
* to be able to send witnesses to other nodes.
* to verify the witness root hash of the blocks
I suppose that it's important to verify the witness root hash because
a bad peer may send me invalid witnesses during initial block
download, and if I don't verify that the witness root hash actually
commits to them, I will get banned by peers requesting the blocks from
me because I send them garbage.
So both the reasons above (there may be more that I don't know about)
are actually the same reason: To be able to send witnesses to others
without getting banned.
What if a node could chose not to download witnesses and thus chose to
send only witnessless blocks to peers. Let's call these nodes
witnessless nodes. Note that witnessless nodes are only witnessless
for blocks up to X. Everything after X is fully verified.
Witnessless nodes would be able to sync faster because it needs to
download less data to calculate their UTXO set. They would therefore
more quickly be able to provide full service to SPV wallets and its
local wallets as well as serving blocks to other witnessless nodes
with same or higher assumevalid block. For witnessless nodes with
lower assumevalid they can serve at least some blocks. It could also
serve blocks to non-segwit nodes.
Do witnessless nodes risk dividing the network in two parts, one
witnessless and one with full nodes, with few connections between the
parts?
So basically, what are the reasons not to implement witnessless
nodes?
Thank you,
/Kalle
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2023-06-07 18:05:08

- reply

📅 Original date posted:2017-08-28
📝 Original message:2017-08-28 19:12 GMT+02:00 Gregory Maxwell via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org>:
>
> The bits field can only change every 2016 blocks (4 bytes per header),
> the timestamp can not be less than the median of the last 11 and is
> usually only a small amount over the last one (saves 2 bytes per
> header), the block version is usually one of the last few (save 3
> bytes per header).
>
... and I guess the nonce can be arbitrarily truncated as well, just brute
force the missing bits :-P.
> But all these things improvements are just a constant factor. I think
> you want the compact SPV proofs described in the appendix of the
> sidechains whitepaper which creates log scaling proofs.
>
I think that my blog post on compact spv proofs can be helpful also. It
tries to make the pretty compact formulations in the sidechains paper a bit
more graspable by normal people.
http://popeller.io/index.php/2016/09/15/compact-spv-proofs/
Kalle
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2023-06-07 17:41:08

- reply

📅 Original date posted:2015-09-28
📝 Original message:2015-09-27 21:50 GMT+02:00 Gregory Maxwell <gmaxwell at gmail.com>:
> On Sun, Sep 27, 2015 at 3:10 PM, Kalle Rosenbaum via bitcoin-dev
> <bitcoin-dev at lists.linuxfoundation.org> wrote:
> > I was mansplaining weak blocks to my wife. She asked a simple question:
> >
> > Why would I, as a miner, publish a weak block if I find one?
> >
> > I don't know.
> > Sure, I will get faster propagation for my solved block, should I find
> one.
> > On the other hand everybody else mining a similar block will enjoy the
> same
> > benefit. Assuming that I'm not a huge miner, it's unlikely that I will
> > actually solve the block, so I'm probably just giving away fast
> propagation
> > times to someone else.
> > So how does publishing a weak block benefit the producer of it more than
> the
> > other miners? Please help me understand this.
>
> Keep in mind, because of efficient differential transmission the cost
> to you is effectively nothing if your transaction acceptance policy is
> predictable, it's a hand-full of bytes sent. And by failing to send
> yours you do little to nothing to deny others the improvement.
>
>
Suppose that you've solved a block Z (weak or not) and you want to
propagate it using a previous weak block Y. With "efficient differential
transmission", I assume that you refer to the transmission of the
differences between Y and Z to a peer? What encodings are discussed? I
guess IBLTs are a hot candidate, but are there other schemes in the making?
I suppose that sending something like "weak block Y plus transactions A, B,
C minus transaction ids h(D), h(E)" is not considered an efficient
differential transmission. Then that's part of the answer to my question.
> Lets imagine an alternative weak-blockless weak block implementation:
>
> Every N seconds, every miner send to every other miner what they're
> working on. This isn't totally crazy-- efficient differential
> transmission will keep the amount transmitted small.
>
> Any block found can be referenced to any of these earlier worklists.
>
> What the effect be of not transmitting yours?
>
> If your block is unlike everyone elses, you would suffer great delays
> in the event you found a block.
> If your block is mostly like everyone elses, you wouldn't suffer as
> much delay-- but the transmission costs would be negligible in that
> case. ... the size sent is proportional to the improvement you get
> when finding a block.
>
"the size sent is proportional to the improvement you get when finding a
block." - This encapsulates the issue quite well! The more exotic block I'm
building, the more I would benefit from publishing a weak block, but my
weak block would also be larger.
>
> In either case, no one else is harmed by you not sending yours... they
> still send their lists.
>
> A problem with that scheme is that unless you've layered an identity
> based access control system on it anyone can DOS attack it, because
> anyone can send as much as they want, they don't even have to be
> actual miners.
>
> What weak blocks adds to that is using hashcash as a rate limiting
> mechanism-- a coordination free lottery weighed by hash-power decides
> who can transmit.
>
> What if you don't participate in the lottery and share your solutions?
> No major harm for the other users... the other users will just choose
> a somewhat lower weak-block threshold to get the updates at the
> desired rate than they would otherwise. To the extent that what you
> were working on was different from anyone else, you'll suffer because
> you failed to make use of your chance to influence what could be
> efficiently transmitted to include your own blocks.
>
Makes perfect sense. Also, if I'm working on an exotic block, the
probability of someone extending my weak block would be low-ish, so I'm not
necessarily "giving away fast propagation times to someone else" as I first
thought.
> You could also ask a question of why would you transitively relay
> someone elses announcement-- well if it helped their blocks too (by
> reflecting things they also want to mine) the answer is obvious. But
> what if it was disjoint from the things they wanted to mine and didn't
> help compared to the weak blocks they already relayed? In that case
> it's still in likely in their interest to relay it because if a block
> similar to it is produced and they extend that block they may end up
> orphaned because of propagation delays their parent block suffered.
> What if they receive an announcement which is so "ugly" that they
> wouldn't extend the chain with the strong block version of it (they'd
> intentionally try to fork it off?)-- in that case they wouldn't want
> to relay it. So much the same logic as why you relay other parties
> blocks applies, including-- relaying helps the network, but if you
> don't it'll still get along fine without you.
>
Thank you very much for your explanation.
/Kalle
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2023-06-07 17:41:07

- reply

📅 Original date posted:2015-09-27
📝 Original message:I was mansplaining weak blocks to my wife. She asked a simple question:
Why would I, as a miner, publish a weak block if I find one?
I don't know.
Sure, I will get faster propagation for my solved block, should I find one.
On the other hand everybody else mining a similar block will enjoy the same
benefit. Assuming that I'm not a huge miner, it's unlikely that I will
actually solve the block, so I'm probably just giving away fast propagation
times to someone else.
So how does publishing a weak block benefit the producer of it more than
the other miners? Please help me understand this.
/Kalle Rosenbaum
2015-09-27 11:42 GMT+02:00 Tier Nolan via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org>:
>
>
> On Sun, Sep 27, 2015 at 2:39 AM, Gregory Maxwell via bitcoin-dev <
> bitcoin-dev at lists.linuxfoundation.org> wrote:
>
>> Unless the weak block transaction list can be a superset of the block
>> transaction list size proportional propagation costs are not totally
>> eliminated.
>>
>
> The POW threshold could be dynamic. The first weak-block that builds on a
> new block could be forwarded with a smaller target.
>
> This reduces the window size until at least one weak block is
> propagated.
>
> The change in threshold could be time based (for the first 30 seconds or
> so). This would cause a surge of traffic when a new block once a new block
> has propagated, so perhaps not so good an idea.
>
>
>> As even if the weak block criteria is MUCH lower than the block
>> criteria (which would become problematic in its own right at some
>> point) the network will sometimes find blocks when there hasn't been
>> any weak block priming at all (e.g. all prior priming has made it into
>> blocks already).
>>
>
> If there is a transaction backlog, then miners could forward merkle
> branches with transactions in the memory pool with a commitment in the
> coinbase.
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
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2023-06-07 15:43:38

- reply

📅 Original date posted:2015-07-27
📝 Original message:Ok, Thanks
Den 27 jul 2015 11:08 skrev "Jorge Timón" <jtimon at jtimon.cc>:
>
> On Jul 26, 2015 11:13 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
> > Do you think we need a bigger nonce? In that case, why?
>
> I don't know, it wasn't me that proposed a bigger nonce. I just wanted to
> point out that the policy limit shouldn't be a concern.
>
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2023-06-07 15:43:37

- reply

📅 Original date posted:2015-07-26
📝 Original message:(Resending to the new bitcoin-dev list after sending to the old list)
2015-07-25 21:34 GMT+02:00 Jorge Timón <jtimon at jtimon.cc>:
> Then why do you assume they have a policy limit that not even bitcoin core
> itself maintains (the default limit was moved from 42 to 83 [counting the
> op_return and pushes])?
>
> The policy check is not a consensus rule. Other implementations may have
> another default or not have a limit at all.
Thank you for pointing this out.
That's right. Bitcoin core now support 80 bytes data by default. And
yes, I was wrong in assuming 40 bytes policy in all implementations,
even if 40 bytes was the limit in bitcoin core at the time of writing
the BIP.
If there's a need to increase the size of the nonce, for example to
128 bits instead of the 48 bits as designed in BIP 120, then we can of
course do that, either now or in a subsequent version of PoP.
As noted before though, a longer nonce also means bigger QR codes
generated from the BIP 121 URIs. So I think that 48 bits is a good
tradeoff right now. And as stated in BIP120, a server generating PoP
requests should try to detect brute force attacks, or at least delay
the response (containing the nonce) by some 100 ms or so.
Do you think we need a bigger nonce? In that case, why?
If PoP later becomes an extension of BIP70, then there is no such size
constraint on the nonce, since it will be part of some kind of (e.g.)
PopRequest message and not contained in a QR encoded URI.
/Kalle

2023-06-07 15:43:36

- reply

📅 Original date posted:2015-07-24
📝 Original message:These BIPs have been assigned 120 and 121:
120: Proof of Payment
121: Proof of Payment URI scheme
Regards,
Kalle
Den 24 jul 2015 08:27 skrev "Kalle Rosenbaum" <kalle at rosenbaum.se>:
> These BIPs have been assigned 120 and 121:
>
> 120: Proof of Payment
> 121: Proof of Payment URI scheme
>
> Regards,
> Kalle
> Den 21 jun 2015 16:39 skrev "Kalle Rosenbaum" <kalle at rosenbaum.se>:
>
>> Hi Greg!
>>
>> After a lot of constructive discussion, feedback and updating, I'm
>> requesting that you please assign these proposals BIP numbers. It's both
>> the "Proof of Payment" proposal and the "Proof of Payment URI scheme"
>> proposal that I'm referring to.
>>
>> The wikimedia source is available here:
>> https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
>> https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP.
>>
>> Is this what you need in order to proceed or is there something else you
>> need from me?
>>
>> Best regards,
>> /Kalle
>>
>> 2015-06-17 11:51 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>>
>>> 2015-06-16 21:48 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>>> > I don't see why existing software could create a 40-byte OP_RETURN but
>>> not
>>> > larger? The limitation comes from a relay policy in full nodes, not a
>>> > limitation is wallet software... and PoPs are not relayed on the
>>> network.
>>>
>>> You are probably right here. The thing is that I don't know how *all*
>>> wallet signing and validating software is written, so I figure it's
>>> better to stick to a "valid" output. Since I don't *need* more data
>>> than 40 bytes, why bother. There's another constraint to this as well:
>>> The other BIP proposal, "Proof of Payment URI scheme", includes a
>>> nonce parameter in the URI. If the nonce is very long, the QR code
>>> will be unnecessarily big. The server should try to detect a brute
>>> force of the 48 bit nonce, or at least delay the pop requests by some
>>> 100 ms or so.
>>>
>>> Do you think this is an actual problem, and why? Is your suggestion to
>>> use a bigger nonce, given the above?
>>>
>>> >
>>> > Regarding sharing, I think you're talking about a different use case.
>>> Say
>>> > you want to pay for 1-week valid entrance to some venue. I thought the
>>> > purpose of the PoP was to be sure that only the person who paid for
>>> it, and
>>> > not anyone else can use it during that week.
>>> >
>>>
>>> That's right. That's one use case. You pay for the 1-week entrance and
>>> then you use your wallet to sign PoPs when you enter the venue.
>>>
>>> > My argument against that is that the original payer can also hand the
>>> > private keys in his wallet to someone else, who would then become able
>>> to
>>> > create PoPs for the service. He does not lose anything by this,
>>> assuming the
>>> > address is not reused.
>>> >
>>>
>>> Yes, that is possible. It's about the same as giving out a
>>> username/password for a service that you have paid for. In the case of
>>> a concert ticket, it's simple. Just allow one entrance per payment.
>>> But in the example you gave, it's a bit more complicated. You could
>>> for example give all guests a bracelet upon first entry or upon first
>>> exit. Or you can put a stamp on people leaving the venue, and demand
>>> that all re-entries show the stamp, possibly along with a new PoP.
>>> Pretty much as is done already. Different use cases will need
>>> different protection. In this example, the value added by PoP is that
>>> the venue does not have to distribute tickets in advance. This in turn
>>> allows for better privacy for the customer, who don't have to give out
>>> personal information such as an email-address.
>>>
>>> > So, using a token does not change anything, except it can be provided
>>> to the
>>> > payer - instead of relying on creating an implicit identity based on
>>> who
>>> > seems to have held particular private keys in the past.
>>> >
>>>
>>> Yes, that's a difference, but it comes at the cost of security. The
>>> stolen token can be used over and over. In the case of PoP it's only
>>> usable once, and it's only created when it's actually needed,
>>> minimizing the window of opportunity for the thief.
>>>
>>> Regards,
>>> Kalle
>>>
>>> > On Jun 16, 2015 9:41 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>> >>
>>> >> 2015-06-16 21:25 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>>> >> > You can't avoid sharing the token, and you can't avoid sharing the
>>> >> > private
>>> >> > keys used for signing either. If they are single use, you don't lose
>>> >> > anything by sharing them.
>>> >>
>>> >> Forwarding the PoP request would be a way to avoid sharing keys, as
>>> >> suggested above.
>>> >>
>>> >> >
>>> >> > Also you are not creating a real transaction. Why does the OP_RETURN
>>> >> > limitation matter?
>>> >>
>>> >> This was discussed in the beginning of this thread: "The idea is to
>>> >> simplify implementation. Existing software can be used as is to sign
>>> >> and validate PoPs"
>>> >>
>>> >> Regards,
>>> >> Kalle
>>> >>
>>> >> >
>>> >> > On Jun 16, 2015 9:22 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se>
>>> wrote:
>>> >> >>
>>> >> >> Thank you for your comments Pieter! Please find my answers below.
>>> >> >>
>>> >> >> 2015-06-16 16:31 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com
>>> >:
>>> >> >> > On Mon, Jun 15, 2015 at 1:59 PM, Kalle Rosenbaum <
>>> kalle at rosenbaum.se>
>>> >> >> > wrote:
>>> >> >> >>
>>> >> >> >> 2015-06-15 12:00 GMT+02:00 Pieter Wuille <
>>> pieter.wuille at gmail.com>:
>>> >> >> >> I'm not sure if we will be able to support PoP with CoinJoin.
>>> Maybe
>>> >> >> >> someone with more insight into CoinJoin have some input?
>>> >> >> >
>>> >> >> >
>>> >> >> > Not really. The problem is that you assume a transaction
>>> corresponds
>>> >> >> > to
>>> >> >> > a
>>> >> >> > single payment. This is true for simple wallet use cases, but not
>>> >> >> > compatible
>>> >> >> > with CoinJoin, or with systems that for example would want to
>>> combine
>>> >> >> > multiple payments in a single transaction.
>>> >> >> >
>>> >> >>
>>> >> >> Yes, you are right. It's not compatible with CoinJoin and the
>>> likes.
>>> >> >>
>>> >> >> >
>>> >> >> > 48 bits seems low to me, but it does indeed solve the problem.
>>> Why
>>> >> >> > not
>>> >> >> > 128
>>> >> >> > or 256 bits?
>>> >> >>
>>> >> >> The nonce is limited because of the OP_RETURN output being limited
>>> to
>>> >> >> 40 bytes of data: 2 bytes version, 32 bytes txid, 6 bytes nonce.
>>> >> >>
>>> >> >> >
>>> >> >> >> > Why does anyone care who paid? This is like walking into a
>>> >> >> >> > coffeshop,
>>> >> >> >> > noticing I don't have money with me, let me friend pay for
>>> me, and
>>> >> >> >> > then
>>> >> >> >> > have
>>> >> >> >> > the shop insist that I can't drink it because I'm not the
>>> buyer.
>>> >> >> >>
>>> >> >> >> If you pay as you use the service (ie pay for coffee upfront),
>>> >> >> >> there's
>>> >> >> >> no need for PoP. Please see the Motivation section. But you are
>>> >> >> >> right
>>> >> >> >> that you must have the wallet(s) that paid at hand when you
>>> issue a
>>> >> >> >> PoP.
>>> >> >> >>
>>> >> >> >> >
>>> >> >> >> > Track payments, don't try to assign identities to payers.
>>> >> >> >>
>>> >> >> >> Please elaborate, I don't understand what you mean here.
>>> >> >> >
>>> >> >> >
>>> >> >> > I think that is a mistake. You should not assume that the wallet
>>> who
>>> >> >> > held
>>> >> >> > the coins is the payer/buyer. That's what I said earlier; you're
>>> >> >> > implicitly
>>> >> >> > creating an identity (the one who holds these keys) based on the
>>> >> >> > transaction. This seems fundamentally wrong to me, and not
>>> necessary.
>>> >> >> > The
>>> >> >> > receiver should not care who paid or how, he should care what was
>>> >> >> > payed
>>> >> >> > for.
>>> >> >>
>>> >> >> You are saying that it's a problem that the wallet used to pay,
>>> must
>>> >> >> also be used to issue the PoP? That may very well be a problem in
>>> some
>>> >> >> cases. People using PoP should of course be aware of it's
>>> limitations
>>> >> >> and act accordingly, i.e. don't pay for concert tickets for a
>>> friend
>>> >> >> and expect your friend to be able to enter the arena with her
>>> wallet.
>>> >> >> As Tom Harding noted, it is possible to transfer keys to your
>>> friend's
>>> >> >> wallet, but that might not be desirable if those keys are also used
>>> >> >> for other payments. Also that would weaken the security of an HD
>>> >> >> wallet, since a chain code along with a private key would reveal
>>> all
>>> >> >> keys in that tree. Another solution is that your friend forwards
>>> the
>>> >> >> PoP request to your wallet, through twitter or SMS, and you send
>>> the
>>> >> >> PoP for her. Maybe that forwarding mechanism can be built into
>>> wallets
>>> >> >> and automated so that the wallet automatically suggests to sign the
>>> >> >> PoP for your friend. This is probably something to investigate
>>> >> >> further, but not within the scope of this BIP.
>>> >> >>
>>> >> >> Of course the simplest solution would be to send money to your
>>> friend
>>> >> >> first so that she can pay for the ticket from her own wallet, but
>>> >> >> that's not always feasible.
>>> >> >>
>>> >> >> >
>>> >> >> > The easiest solution to this IMHO would be an extension to the
>>> >> >> > payment
>>> >> >> > protocol that gives you (or your wallet) a token in return for
>>> >> >> > paying,
>>> >> >> > and
>>> >> >> > that knowledge of that token is used to gain access to the
>>> services
>>> >> >> > you
>>> >> >> > provide.
>>> >> >> >
>>> >> >>
>>> >> >> That token would then be reusable. Someone stealing it would be
>>> able
>>> >> >> to use it as much as she wants. That is what I want to avoid with
>>> PoP.
>>> >> >> The BIP proposal briefly mentions something like this in the
>>> >> >> rationale. I also had a discussion about this with Mike Hearn on
>>> this
>>> >> >> list on Mars 13 that I think covers most pros and cons of the
>>> >> >> different approaches.
>>> >> >>
>>> >> >> While your suggestion does indeed separate the transaction from the
>>> >> >> proof of payment, it also assumes that the token is held in the
>>> wallet
>>> >> >> that pays. Otherwise you would need to keep it in another safe
>>> place,
>>> >> >> remember it's reusable. Where would that be? How would you transfer
>>> >> >> that token to your friend?
>>> >> >>
>>> >> >> Thank you again for your comments. I appreciate it.
>>> >> >>
>>> >> >> Best regards,
>>> >> >> Kalle
>>> >> >>
>>> >> >> > --
>>> >> >> > Pieter
>>> >> >> >
>>>
>>
>>
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2023-06-07 15:43:16

- reply

📅 Original date posted:2015-07-23
📝 Original message:Hi all
I suggest that we add to the "BIP Editor Responsibilities & Workflow"
section of BIP0001 that if the BIP editor for some reason won't handle
the BIP within a week, he/she should notify the author within that
same week with an estimate on when it will be handled.
Maybe we could extend it to two weeks instead, the important thing is
that the author knows what to expect.
I'm trying to get BIP numbers allocated for Proof of Payment. I have
requested it from the BIP editor Gregory Maxwell with CC this list. I
also emailed Gregory in private about it. So far I have not seen any
reaction to my requests.
There are a number of BIP proposals floating arount right now, I don't
know the exact status of them all, but this is roughly how it looks
for some of them:
Date of request, bip#, Author, Title
july 4, -, Gregory Maxwell, Invalid Block Fork Postmortem
june 29, -, Peter Todd, Full Replace-by-Fee Deployment Schedule
june 22, 101, Gavin Andresen, Increase Maximum Block Size
june 17, 68, Mark Friedenbach, Consensus-enforced transaction
replacement signalled via sequence numbers
june 6, -,Kalle Rosenbaum, Proof of Payment
june 6, -,Kalle Rosenbaum, Proof of Payment URI scheme
june 6, 69?, Kristov Atlas, Lexicographical Indexing of Transaction
Inputs and Outputs
I think that the de facto process for BIP allocation and inclusion in
the bips repository is unclear. When a number is requested, the author
should at least get a reply from the bip editor that the request is
seen by him/her. Also, if the editor disapproves on the BIP for some
reason, the author must be notified somehow within reasonable and
predictable time.
Regards,
Kalle

2023-06-07 15:43:16

- reply

📅 Original date posted:2015-07-23
📝 Original message:A PoP-enabled fork of Mycelium is available at
https://github.com/kallerosenbaum/wallet and the server (validating
code) is available at https://github.com/kallerosenbaum/poppoc/
There's also a demo site using the server code at
http://www.rosenbaum.se:8080/ and a demo video at
https://www.youtube.com/watch?v=euzZcoCilhc
Mycelium Binaries are also available on the demo site.
Regards,
Kalle
2015-07-23 21:29 GMT+02:00, Peter Todd <pete at petertodd.org>:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
>
>
> On 23 July 2015 06:21:55 GMT-04:00, Kalle Rosenbaum via bitcoin-dev
> <bitcoin-dev at lists.linuxfoundation.org> wrote:
>>Hi all
>>
>>I suggest that we add to the "BIP Editor Responsibilities & Workflow"
>>section of BIP0001 that if the BIP editor for some reason won't handle
>>the BIP within a week, he/she should notify the author within that
>>same week with an estimate on when it will be handled.
>>
>>Maybe we could extend it to two weeks instead, the important thing is
>>that the author knows what to expect.
>>
>>I'm trying to get BIP numbers allocated for Proof of Payment. I have
>>requested it from the BIP editor Gregory Maxwell with CC this list. I
>>also emailed Gregory in private about it. So far I have not seen any
>>reaction to my requests.
>
> To be clear, where is an implementation of your proposed BIP?
>
> The philosophy of the process - particularly for non-consensus BIPs - is
> running code, preferably in production. An actual number for the standard
> that code implements isn't a barrier to that process.
>
> Remember that it's convenient for all if the number of BIPs out there isn't
> significantly higher than the number of actual standards in place that are
> being used.
>
>
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>
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> =RW4h
> -----END PGP SIGNATURE-----
>
>

2023-06-07 15:39:59

- reply

📅 Original date posted:2015-06-25
📝 Original message:2015-06-23 7:53 GMT+02:00 Rusty Russell <rusty at rustcorp.com.au>:
> Hi all,
>
> I've come up with a model for using IBLT to communicate blocks
> between peers. The gory details can be found on github: it's a
> standalone C++ app for testing not integrated with bitcoin.
>
> https://github.com/rustyrussell/bitcoin-iblt
Good to see that you're working on this. Really exciting!
I want to take the opportunity to link to my previous work on IBLTs, for
those that haven't seen it, where I investigate the behaviour of the IBLT
when changing different parameters, like cell count, hashFunctionCount etc:
https://github.com/kallerosenbaum/bitcoin-iblt/wiki
>From glancing over your implementation, I see that you don't use a
keyHashSum, in fact you don't use a key at all, but only a
concatenatenation of (txid48, fragid, tx-chunk) as value. Here the
txid48+fragid functions as a kind of keyHashSum. I think this might be a
very good idea,
If you have a false positive with count == 1, then you would probably
detect it if fragid is outside reasonable limit from from base_fragid. Did
you implement your idea to remove all the count==1 fagments in ascending
order of (fragid-base_fragid)?
Anyhow, I think we should make some more comparable tests, just as you
proposed last year when I didn't reply, sorry... My code is a more straight
forward implementation of the IBLT paper (http://arxiv.org/pdf/1101.2245.pdf)
and encoding blocks is done pretty much as Gavin proposed in his gist. That
should function as a baseline so that we can validate that your
optimizations actually work. Please contact me directly if you are
interested in that, and we'll figure something out.
More comments/questions inline:
>
> Assumptions and details:
>
> 1. The base idea comes from Gavin's Block Propagation gist:
> https://gist.github.com/gavinandresen/e20c3b5a1d4b97f79ac2
>
> 2. It relies on similarity in mempools, with some selection hints. This
> is designed to be as flexible as possible to make fewest assumptions
> on tx selection policy.
>
> 3. The selection hints are: minimum fee-per-byte (fixed point) and
> bitmaps of included-despite-that and rejected-despite-that. The
> former covers things like child-pays-for-parent and the priority
> area. The latter covers other cases like Eligius censoring "spam",
> bitcoin version differences, etc.
>
There is a chance that the bit prefix of the added or removed tx is not
unique within the receiver's mempool. In that case the receiver can
probably just use the earliest matching transaction and hope for the best.
If not -> bad luck. Is that how you do it?
> 4. Cost to represent these exceptional added or excluded transactions is
> (on average) log2(transactions in mempool) bits.
These exceptional tx *could* instead be encoded in the IBLT, just as if
they were unknown differences. Your bitmaps is probably a more compact
representation, but it's also more complex.
>
> 5. At Peiter Wuille's suggestion, it is designed to be reencoded between
> nodes. It seems fast enough for that, and neighboring nodes should
> have most similar mempools.
>
What is the purpose of reencoding when relaying? Is that to improve the
failure probability as new tx may have arrived in the mempool of the
intermediary node?
> 6. It performs reasonably well on my 100 block sample in bitcoin-corpus
> (chosen to include a mempool spike):
>
> Average block range (bytes): 7988-999829
> Block size mean (bytes): 401926
>
> Minimal decodable BLT size range (bytes): 314-386361
> Minimal decodable BLT size mean (bytes): 13265
>
> 7. Actual results will have to be worse than these minima, as peers will
> have to oversize the IBLT to have reasonable chance of success.
>
Yes, I have made some analysis on this here:
https://github.com/kallerosenbaum/bitcoin-iblt/wiki/FailureProbability. We
use quite different data structures for encoding blocks in IBLT, but it
might apply to your implementation as well. An interesting result is that
the space saving percentage actually increases as blocks grow.
> 8. There is more work to do, and more investigation to be done, but I
> don't expect more than a 25% reduction in this "ideal minimum"
> result.
>
> Special thanks to Kalle Rosenbaum for helping investigate IBLTs with me
> last year.
Thank you too!
Regards,
Kalle
>
> Cheers,
> Rusty.
> PS. I work for Blockstream. And I'm supposed to be working on
> Lightning, not this.
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2023-06-07 15:39:43

- reply

📅 Original date posted:2015-06-22
📝 Original message:Thank you!
A few questions/comments:
* In the specification, you refer to "t_start". I guess you mean "time_start"?
* Miners can, especially when close to a block doubling or shortly
after activation, to some extent manipulate max block size by
manipulating the time stamp in the block header within valid limits.
According to the pseudo code in the specification, the first and a
handful of subsequent blocks after activation could actually have
negative max block sizes due to this (depending on how you define the
% operator of the pseudo code). I haven't checked the reference
implementation, but I do think that the specification section should
explicitly handle this.
Regards,
Kalle
2015-06-22 20:18 GMT+02:00 Gavin Andresen <gavinandresen at gmail.com>:
> I promised to write a BIP after I'd implemented
> increase-the-maximum-block-size code, so here it is. It also lives at:
> https://github.com/gavinandresen/bips/blob/blocksize/bip-8MB.mediawiki
>
> I don't expect any proposal to please everybody; there are unavoidable
> tradeoffs to increasing the maximum block size. I prioritize implementation
> simplicity -- it is hard to write consensus-critical code, so simpler is
> better.
>
>
>
>
> BIP: ??
> Title: Increase Maximum Block Size
> Author: Gavin Andresen <gavinandresen at gmail.com>
> Status: Draft
> Type: Standards Track
> Created: 2015-06-22
>
> ==Abstract==
>
> This BIP proposes replacing the fixed one megabyte maximum block size with a
> maximum size that grows over time at a predictable rate.
>
> ==Motivation==
>
> Transaction volume on the Bitcoin network has been growing, and will soon
> reach the one-megabyte-every-ten-minutes limit imposed by the one megabyte
> maximum block size. Increasing the maximum size reduces the impact of that
> limit on Bitcoin adoption and growth.
>
> ==Specification==
>
> After deployment on the network (see the Deployment section for details),
> the maximum allowed size of a block on the main network shall be calculated
> based on the timestamp in the block header.
>
> The maximum size shall be 8,000,000 bytes at a timestamp of 2016-01-11
> 00:00:00 UTC (timestamp 1452470400), and shall double every 63,072,000
> seconds (two years, ignoring leap years), until 2036-01-06 00:00:00 UTC
> (timestamp 2083190400). The maximum size of blocks in between doublings will
> increase linearly based on the block's timestamp. The maximum size of blocks
> after 2036-01-06 00:00:00 UTC shall be 8,192,000,000 bytes.
>
> Expressed in pseudo-code, using integer math:
>
> function max_block_size(block_timestamp):
>
> time_start = 1452470400
> time_double = 60*60*24*365*2
> size_start = 8000000
> if block_timestamp >= time_start+time_double*10
> return size_start * 2^10
>
> // Piecewise-linear-between-doublings growth:
> time_delta = block_timestamp - t_start
> doublings = time_delta / time_double
> remainder = time_delta % time_double
> interpolate = (size_start * 2^doublings * remainder) / time_double
> max_size = size_start * 2^doublings + interpolate
>
> return max_size
>
> ==Deployment==
>
> Deployment shall be controlled by hash-power supermajority vote (similar to
> the technique used in BIP34), but the earliest possible activation time is
> 2016-01-11 00:00:00 UTC.
>
> Activation is achieved when 750 of 1,000 consecutive blocks in the best
> chain have a version number with bits 3 and 14 set (0x20000004 in hex). The
> activation time will be the timestamp of the 750'th block plus a two week
> (1,209,600 second) grace period to give any remaining miners or services
> time to upgrade to support larger blocks. If a supermajority is achieved
> more than two weeks before 2016-01-11 00:00:00 UTC, the activation time will
> be 2016-01-11 00:00:00 UTC.
>
> Block version numbers are used only for activation; once activation is
> achieved, the maximum block size shall be as described in the specification
> section, regardless of the version number of the block.
>
>
> ==Rationale==
>
> The initial size of 8,000,000 bytes was chosen after testing the current
> reference implementation code with larger block sizes and receiving feedback
> from miners stuck behind bandwidth-constrained networks (in particular,
> Chinese miners behind the Great Firewall of China).
>
> The doubling interval was chosen based on long-term growth trends for CPU
> power, storage, and Internet bandwidth. The 20-year limit was chosen because
> exponential growth cannot continue forever.
>
> Calculations are based on timestamps and not blockchain height because a
> timestamp is part of every block's header. This allows implementations to
> know a block's maximum size after they have downloaded it's header, but
> before downloading any transactions.
>
> The deployment plan is taken from Jeff Garzik's proposed BIP100 block size
> increase, and is designed to give miners, merchants, and
> full-node-running-end-users sufficient time to upgrade to software that
> supports bigger blocks. A 75% supermajority was chosen so that one large
> mining pool does not have effective veto power over a blocksize increase.
> The version number scheme is designed to be compatible with Pieter's
> Wuille's proposed "Version bits" BIP.
>
> TODO: summarize objections/arguments from
> http://gavinandresen.ninja/time-to-roll-out-bigger-blocks.
>
> TODO: describe other proposals and their advantages/disadvantages over this
> proposal.
>
>
> ==Compatibility==
>
> This is a hard-forking change to the Bitcoin protocol; anybody running code
> that fully validates blocks must upgrade before the activation time or they
> will risk rejecting a chain containing larger-than-one-megabyte blocks.
>
> Simplified Payment Verification software is not affected, unless it makes
> assumptions about the maximum depth of a transaction's merkle branch based
> on the minimum size of a transaction and the maximum block size.
>
> ==Implementation==
>
> https://github.com/gavinandresen/bitcoinxt/tree/blocksize_fork
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

2023-06-07 15:37:00

- reply

📅 Original date posted:2015-06-06
📝 Original message:Hi
Following earlier posts on Proof of Payment I'm now proposing the following
BIP for a Proof of Payment URI scheme (To read it formatted instead, go to
https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP).
Regards,
Kalle Rosenbaum
<pre>
BIP: <BIP number>
Title: Proof of Payment URI scheme
Author: Kalle Rosenbaum <kalle at rosenbaum.se>
Status: Draft
Type: Standards Track
Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
</pre>
== Abstract ==
This is a proposal for a URI scheme to be used in the Proof of Payment
process.
== Motivation ==
To make a Proof of Payment, the party that wants the proof needs to
transfer a Proof of Payment request to the wallet software of the
other party. To facilitate that transfer, a new URI scheme
representing the PoP request is proposed. This URI can then be encoded
in QR images or sent over NFC in order to transfer it to the wallet.
== Specification ==
The specification is the same as BIP0021, with the following
differences:
* The URI scheme is <tt>btcpop</tt> instead of <tt>bitcoin</tt>
* The path component, i.e. the address part, is always empty.
* A mandatory <tt>p</tt> parameter whose value contains the destination for
the PoP. This could for example be a <tt>https:</tt> URL or a <tt>mailto:</tt>
URI.
* A mandatory <tt>n</tt> parameter representing the nonce, base58 encoded.
* An optional <tt>txid</tt> parameter containing the Base58 encoded hash of
the transaction to prove.
Just as in BIP0021, elements of the query component may contain
characters outside the valid range. These must first be encoded
according to UTF-8, and then each octet of the corresponding UTF-8
sequence must be percent-encoded as described in RFC 3986.
All parameters except <tt>p</tt> and <tt>n</tt> are hints to the
wallet on which transaction to create a PoP for.
The extensibility of BIP0021 applies to this scheme as well. For
example, a <tt>date</tt> parameter or a <tt>toaddr</tt> parameter
might be useful. <tt>req-*</tt> parameters are also allowed and obey
the same rules as in BIP0021, clients not supporting a <tt>req-*</tt>
parameter must consider the URI invalid.
=== Keep URIs short ===
Implementations should keep the URIs as short as possible. This is
because it makes QR decoding more stable. A camera with a scratched
lens or low resolution may run into problems scanning huge QR
codes. This is why the <tt>txid</tt> parameter is encoded in Base58
instead of the classic hex encoded string. We get away with 44
characters instead of 64. Also, the <tt>nonce</tt> parameter is Base58
encoded for the same reason.
== Interpretation ==
=== Transaction hints ===
The wallet processing the URI must use the hints in the PoP request to
filter its transaction set. The <tt>label</tt>, <tt>amount</tt> and
<tt>message</tt> parameters must, if present in the URI, exactly match
the data associated with the original payment according to the
following table:
{|
| <tt>btcpop:</tt> URI parameter || <tt>bitcoin:</tt> URI parameter ||
BIP70 PaymentDetails data
|-
| <tt>label</tt> || <tt>label</tt> ||
<tt>merchant_data</tt>
|-
| <tt>amount</tt> || <tt>amount</tt> ||
<tt>sum of outputs.amount</tt>
|-
| <tt>message</tt> || <tt>message</tt> ||
<tt>memo</tt>
|}
The <tt>txid</tt> parameter value must match the transaction hash of
the payment.
After filtering, the resulting transaction set is displayed to the
user who selects one of them to prove. An implementation could also
automatically select a transaction in the filtered set, but
there must still be a way for the user to select freely among the
matching transactions. If the filtered set is empty, no transaction
fits the hints and a message about that is presented to the user. If
the filtered set contains exactly one transaction, which is
preferable, that transaction can be automatically selected.
As a fallback, there must also be a way for the user to select any
transaction from the wallet regardless of the transaction hints. This
can be useful if the metadata of the wallet is lost, possibly due to a
restore from backup.
=== PoP destination <tt>p</tt> ===
The <tt>p</tt> parameter value is the destination where to send the
PoP to. This destination is typically a <tt>https:</tt> URL or a
<tt>http:</tt> URL, but it could be any type of URI, for example
<tt>mailto:</tt>. To keep <tt>btcpop:</tt> URIs short, users should
not make their <tt>p</tt> parameter unneccesarily long.
==== <tt>http:</tt> and <tt>https:</tt> URLs ====
Wallet implementations must support the <tt>http:</tt> and
<tt>https:</tt> schemes in which case <tt>POST</tt> method must be
used. The content type of the POST request must be set to
Content-Type: application/bitcoin-pop
Content-Transfer-Encoding: binary
== Examples ==
Send PoP for a transaction with label "video 42923" to
<tt>https://www.example.com/pop/352</tt>, using nonce <tt>0x73 0xd5
0x1a 0xbb 0xd8 0x9c</tt>:
btcpop:?p=https://www.example.com/pop/352&n=zgWTm8yH&label=video 42923
Send PoP through mail using
<tt>mailto:pop at example.com?subject=pop444</tt>, amount is 13370000
satoshis, nonce is <tt>0x6f 0xe 0xfb 0x68 0x92 0xf9</tt>. Note that
the <tt>?</tt> before <tt>subject</tt> is OK according to RFC3986,
since the query part starts from the first <tt>?</tt>:
btcpop:?p=mailto:pop at example.com?subject%3Dpop444&n=xJdKmEbr&amount=0.1337
Send PoP for transaction with id
<tt>cca7507897abc89628f450e8b1e0c6fca4ec3f7b34cccf55f3f531c659ff4d79</tt>
to pizza place at <tt>http://pizza.example.com/pop/laszlo111</tt>
using nonce <tt>0xfc 0xcc 0x2c 0x35 0xf0 0xb8</tt>
btcpop:?p=
http://pizza.example.com/pop/laszlo111&n=3AtNpVrPh&txid=Emt9MPvt1joznqHy5eEHkNtcuQuYWXzYJBQZN6BJm6NL
== Reference implementation ==
[https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
[https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
== References ==
[https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki BIP21]: URI
Scheme
[[Proof of Payment BIP]]
[https://www.ietf.org/rfc/rfc3986.txt RFC3986]: Uniform Resource Identifier
(URI): Generic Syntax
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2023-06-07 15:36:59

- reply

📅 Original date posted:2015-06-21
📝 Original message:Hi Greg!
After a lot of constructive discussion, feedback and updating, I'm
requesting that you please assign these proposals BIP numbers. It's both
the "Proof of Payment" proposal and the "Proof of Payment URI scheme"
proposal that I'm referring to.
The wikimedia source is available here:
https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP.
Is this what you need in order to proceed or is there something else you
need from me?
Best regards,
/Kalle
2015-06-17 11:51 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
> 2015-06-16 21:48 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
> > I don't see why existing software could create a 40-byte OP_RETURN but
> not
> > larger? The limitation comes from a relay policy in full nodes, not a
> > limitation is wallet software... and PoPs are not relayed on the network.
>
> You are probably right here. The thing is that I don't know how *all*
> wallet signing and validating software is written, so I figure it's
> better to stick to a "valid" output. Since I don't *need* more data
> than 40 bytes, why bother. There's another constraint to this as well:
> The other BIP proposal, "Proof of Payment URI scheme", includes a
> nonce parameter in the URI. If the nonce is very long, the QR code
> will be unnecessarily big. The server should try to detect a brute
> force of the 48 bit nonce, or at least delay the pop requests by some
> 100 ms or so.
>
> Do you think this is an actual problem, and why? Is your suggestion to
> use a bigger nonce, given the above?
>
> >
> > Regarding sharing, I think you're talking about a different use case. Say
> > you want to pay for 1-week valid entrance to some venue. I thought the
> > purpose of the PoP was to be sure that only the person who paid for it,
> and
> > not anyone else can use it during that week.
> >
>
> That's right. That's one use case. You pay for the 1-week entrance and
> then you use your wallet to sign PoPs when you enter the venue.
>
> > My argument against that is that the original payer can also hand the
> > private keys in his wallet to someone else, who would then become able to
> > create PoPs for the service. He does not lose anything by this, assuming
> the
> > address is not reused.
> >
>
> Yes, that is possible. It's about the same as giving out a
> username/password for a service that you have paid for. In the case of
> a concert ticket, it's simple. Just allow one entrance per payment.
> But in the example you gave, it's a bit more complicated. You could
> for example give all guests a bracelet upon first entry or upon first
> exit. Or you can put a stamp on people leaving the venue, and demand
> that all re-entries show the stamp, possibly along with a new PoP.
> Pretty much as is done already. Different use cases will need
> different protection. In this example, the value added by PoP is that
> the venue does not have to distribute tickets in advance. This in turn
> allows for better privacy for the customer, who don't have to give out
> personal information such as an email-address.
>
> > So, using a token does not change anything, except it can be provided to
> the
> > payer - instead of relying on creating an implicit identity based on who
> > seems to have held particular private keys in the past.
> >
>
> Yes, that's a difference, but it comes at the cost of security. The
> stolen token can be used over and over. In the case of PoP it's only
> usable once, and it's only created when it's actually needed,
> minimizing the window of opportunity for the thief.
>
> Regards,
> Kalle
>
> > On Jun 16, 2015 9:41 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
> >>
> >> 2015-06-16 21:25 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
> >> > You can't avoid sharing the token, and you can't avoid sharing the
> >> > private
> >> > keys used for signing either. If they are single use, you don't lose
> >> > anything by sharing them.
> >>
> >> Forwarding the PoP request would be a way to avoid sharing keys, as
> >> suggested above.
> >>
> >> >
> >> > Also you are not creating a real transaction. Why does the OP_RETURN
> >> > limitation matter?
> >>
> >> This was discussed in the beginning of this thread: "The idea is to
> >> simplify implementation. Existing software can be used as is to sign
> >> and validate PoPs"
> >>
> >> Regards,
> >> Kalle
> >>
> >> >
> >> > On Jun 16, 2015 9:22 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se>
> wrote:
> >> >>
> >> >> Thank you for your comments Pieter! Please find my answers below.
> >> >>
> >> >> 2015-06-16 16:31 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
> >> >> > On Mon, Jun 15, 2015 at 1:59 PM, Kalle Rosenbaum <
> kalle at rosenbaum.se>
> >> >> > wrote:
> >> >> >>
> >> >> >> 2015-06-15 12:00 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com
> >:
> >> >> >> I'm not sure if we will be able to support PoP with CoinJoin.
> Maybe
> >> >> >> someone with more insight into CoinJoin have some input?
> >> >> >
> >> >> >
> >> >> > Not really. The problem is that you assume a transaction
> corresponds
> >> >> > to
> >> >> > a
> >> >> > single payment. This is true for simple wallet use cases, but not
> >> >> > compatible
> >> >> > with CoinJoin, or with systems that for example would want to
> combine
> >> >> > multiple payments in a single transaction.
> >> >> >
> >> >>
> >> >> Yes, you are right. It's not compatible with CoinJoin and the likes.
> >> >>
> >> >> >
> >> >> > 48 bits seems low to me, but it does indeed solve the problem. Why
> >> >> > not
> >> >> > 128
> >> >> > or 256 bits?
> >> >>
> >> >> The nonce is limited because of the OP_RETURN output being limited to
> >> >> 40 bytes of data: 2 bytes version, 32 bytes txid, 6 bytes nonce.
> >> >>
> >> >> >
> >> >> >> > Why does anyone care who paid? This is like walking into a
> >> >> >> > coffeshop,
> >> >> >> > noticing I don't have money with me, let me friend pay for me,
> and
> >> >> >> > then
> >> >> >> > have
> >> >> >> > the shop insist that I can't drink it because I'm not the buyer.
> >> >> >>
> >> >> >> If you pay as you use the service (ie pay for coffee upfront),
> >> >> >> there's
> >> >> >> no need for PoP. Please see the Motivation section. But you are
> >> >> >> right
> >> >> >> that you must have the wallet(s) that paid at hand when you issue
> a
> >> >> >> PoP.
> >> >> >>
> >> >> >> >
> >> >> >> > Track payments, don't try to assign identities to payers.
> >> >> >>
> >> >> >> Please elaborate, I don't understand what you mean here.
> >> >> >
> >> >> >
> >> >> > I think that is a mistake. You should not assume that the wallet
> who
> >> >> > held
> >> >> > the coins is the payer/buyer. That's what I said earlier; you're
> >> >> > implicitly
> >> >> > creating an identity (the one who holds these keys) based on the
> >> >> > transaction. This seems fundamentally wrong to me, and not
> necessary.
> >> >> > The
> >> >> > receiver should not care who paid or how, he should care what was
> >> >> > payed
> >> >> > for.
> >> >>
> >> >> You are saying that it's a problem that the wallet used to pay, must
> >> >> also be used to issue the PoP? That may very well be a problem in
> some
> >> >> cases. People using PoP should of course be aware of it's limitations
> >> >> and act accordingly, i.e. don't pay for concert tickets for a friend
> >> >> and expect your friend to be able to enter the arena with her wallet.
> >> >> As Tom Harding noted, it is possible to transfer keys to your
> friend's
> >> >> wallet, but that might not be desirable if those keys are also used
> >> >> for other payments. Also that would weaken the security of an HD
> >> >> wallet, since a chain code along with a private key would reveal all
> >> >> keys in that tree. Another solution is that your friend forwards the
> >> >> PoP request to your wallet, through twitter or SMS, and you send the
> >> >> PoP for her. Maybe that forwarding mechanism can be built into
> wallets
> >> >> and automated so that the wallet automatically suggests to sign the
> >> >> PoP for your friend. This is probably something to investigate
> >> >> further, but not within the scope of this BIP.
> >> >>
> >> >> Of course the simplest solution would be to send money to your friend
> >> >> first so that she can pay for the ticket from her own wallet, but
> >> >> that's not always feasible.
> >> >>
> >> >> >
> >> >> > The easiest solution to this IMHO would be an extension to the
> >> >> > payment
> >> >> > protocol that gives you (or your wallet) a token in return for
> >> >> > paying,
> >> >> > and
> >> >> > that knowledge of that token is used to gain access to the services
> >> >> > you
> >> >> > provide.
> >> >> >
> >> >>
> >> >> That token would then be reusable. Someone stealing it would be able
> >> >> to use it as much as she wants. That is what I want to avoid with
> PoP.
> >> >> The BIP proposal briefly mentions something like this in the
> >> >> rationale. I also had a discussion about this with Mike Hearn on this
> >> >> list on Mars 13 that I think covers most pros and cons of the
> >> >> different approaches.
> >> >>
> >> >> While your suggestion does indeed separate the transaction from the
> >> >> proof of payment, it also assumes that the token is held in the
> wallet
> >> >> that pays. Otherwise you would need to keep it in another safe place,
> >> >> remember it's reusable. Where would that be? How would you transfer
> >> >> that token to your friend?
> >> >>
> >> >> Thank you again for your comments. I appreciate it.
> >> >>
> >> >> Best regards,
> >> >> Kalle
> >> >>
> >> >> > --
> >> >> > Pieter
> >> >> >
>
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2023-06-07 15:36:58

- reply

📅 Original date posted:2015-06-17
📝 Original message:2015-06-16 21:48 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
> I don't see why existing software could create a 40-byte OP_RETURN but not
> larger? The limitation comes from a relay policy in full nodes, not a
> limitation is wallet software... and PoPs are not relayed on the network.
You are probably right here. The thing is that I don't know how *all*
wallet signing and validating software is written, so I figure it's
better to stick to a "valid" output. Since I don't *need* more data
than 40 bytes, why bother. There's another constraint to this as well:
The other BIP proposal, "Proof of Payment URI scheme", includes a
nonce parameter in the URI. If the nonce is very long, the QR code
will be unnecessarily big. The server should try to detect a brute
force of the 48 bit nonce, or at least delay the pop requests by some
100 ms or so.
Do you think this is an actual problem, and why? Is your suggestion to
use a bigger nonce, given the above?
>
> Regarding sharing, I think you're talking about a different use case. Say
> you want to pay for 1-week valid entrance to some venue. I thought the
> purpose of the PoP was to be sure that only the person who paid for it, and
> not anyone else can use it during that week.
>
That's right. That's one use case. You pay for the 1-week entrance and
then you use your wallet to sign PoPs when you enter the venue.
> My argument against that is that the original payer can also hand the
> private keys in his wallet to someone else, who would then become able to
> create PoPs for the service. He does not lose anything by this, assuming the
> address is not reused.
>
Yes, that is possible. It's about the same as giving out a
username/password for a service that you have paid for. In the case of
a concert ticket, it's simple. Just allow one entrance per payment.
But in the example you gave, it's a bit more complicated. You could
for example give all guests a bracelet upon first entry or upon first
exit. Or you can put a stamp on people leaving the venue, and demand
that all re-entries show the stamp, possibly along with a new PoP.
Pretty much as is done already. Different use cases will need
different protection. In this example, the value added by PoP is that
the venue does not have to distribute tickets in advance. This in turn
allows for better privacy for the customer, who don't have to give out
personal information such as an email-address.
> So, using a token does not change anything, except it can be provided to the
> payer - instead of relying on creating an implicit identity based on who
> seems to have held particular private keys in the past.
>
Yes, that's a difference, but it comes at the cost of security. The
stolen token can be used over and over. In the case of PoP it's only
usable once, and it's only created when it's actually needed,
minimizing the window of opportunity for the thief.
Regards,
Kalle
> On Jun 16, 2015 9:41 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>
>> 2015-06-16 21:25 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>> > You can't avoid sharing the token, and you can't avoid sharing the
>> > private
>> > keys used for signing either. If they are single use, you don't lose
>> > anything by sharing them.
>>
>> Forwarding the PoP request would be a way to avoid sharing keys, as
>> suggested above.
>>
>> >
>> > Also you are not creating a real transaction. Why does the OP_RETURN
>> > limitation matter?
>>
>> This was discussed in the beginning of this thread: "The idea is to
>> simplify implementation. Existing software can be used as is to sign
>> and validate PoPs"
>>
>> Regards,
>> Kalle
>>
>> >
>> > On Jun 16, 2015 9:22 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>> >>
>> >> Thank you for your comments Pieter! Please find my answers below.
>> >>
>> >> 2015-06-16 16:31 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>> >> > On Mon, Jun 15, 2015 at 1:59 PM, Kalle Rosenbaum <kalle at rosenbaum.se>
>> >> > wrote:
>> >> >>
>> >> >> 2015-06-15 12:00 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>> >> >> I'm not sure if we will be able to support PoP with CoinJoin. Maybe
>> >> >> someone with more insight into CoinJoin have some input?
>> >> >
>> >> >
>> >> > Not really. The problem is that you assume a transaction corresponds
>> >> > to
>> >> > a
>> >> > single payment. This is true for simple wallet use cases, but not
>> >> > compatible
>> >> > with CoinJoin, or with systems that for example would want to combine
>> >> > multiple payments in a single transaction.
>> >> >
>> >>
>> >> Yes, you are right. It's not compatible with CoinJoin and the likes.
>> >>
>> >> >
>> >> > 48 bits seems low to me, but it does indeed solve the problem. Why
>> >> > not
>> >> > 128
>> >> > or 256 bits?
>> >>
>> >> The nonce is limited because of the OP_RETURN output being limited to
>> >> 40 bytes of data: 2 bytes version, 32 bytes txid, 6 bytes nonce.
>> >>
>> >> >
>> >> >> > Why does anyone care who paid? This is like walking into a
>> >> >> > coffeshop,
>> >> >> > noticing I don't have money with me, let me friend pay for me, and
>> >> >> > then
>> >> >> > have
>> >> >> > the shop insist that I can't drink it because I'm not the buyer.
>> >> >>
>> >> >> If you pay as you use the service (ie pay for coffee upfront),
>> >> >> there's
>> >> >> no need for PoP. Please see the Motivation section. But you are
>> >> >> right
>> >> >> that you must have the wallet(s) that paid at hand when you issue a
>> >> >> PoP.
>> >> >>
>> >> >> >
>> >> >> > Track payments, don't try to assign identities to payers.
>> >> >>
>> >> >> Please elaborate, I don't understand what you mean here.
>> >> >
>> >> >
>> >> > I think that is a mistake. You should not assume that the wallet who
>> >> > held
>> >> > the coins is the payer/buyer. That's what I said earlier; you're
>> >> > implicitly
>> >> > creating an identity (the one who holds these keys) based on the
>> >> > transaction. This seems fundamentally wrong to me, and not necessary.
>> >> > The
>> >> > receiver should not care who paid or how, he should care what was
>> >> > payed
>> >> > for.
>> >>
>> >> You are saying that it's a problem that the wallet used to pay, must
>> >> also be used to issue the PoP? That may very well be a problem in some
>> >> cases. People using PoP should of course be aware of it's limitations
>> >> and act accordingly, i.e. don't pay for concert tickets for a friend
>> >> and expect your friend to be able to enter the arena with her wallet.
>> >> As Tom Harding noted, it is possible to transfer keys to your friend's
>> >> wallet, but that might not be desirable if those keys are also used
>> >> for other payments. Also that would weaken the security of an HD
>> >> wallet, since a chain code along with a private key would reveal all
>> >> keys in that tree. Another solution is that your friend forwards the
>> >> PoP request to your wallet, through twitter or SMS, and you send the
>> >> PoP for her. Maybe that forwarding mechanism can be built into wallets
>> >> and automated so that the wallet automatically suggests to sign the
>> >> PoP for your friend. This is probably something to investigate
>> >> further, but not within the scope of this BIP.
>> >>
>> >> Of course the simplest solution would be to send money to your friend
>> >> first so that she can pay for the ticket from her own wallet, but
>> >> that's not always feasible.
>> >>
>> >> >
>> >> > The easiest solution to this IMHO would be an extension to the
>> >> > payment
>> >> > protocol that gives you (or your wallet) a token in return for
>> >> > paying,
>> >> > and
>> >> > that knowledge of that token is used to gain access to the services
>> >> > you
>> >> > provide.
>> >> >
>> >>
>> >> That token would then be reusable. Someone stealing it would be able
>> >> to use it as much as she wants. That is what I want to avoid with PoP.
>> >> The BIP proposal briefly mentions something like this in the
>> >> rationale. I also had a discussion about this with Mike Hearn on this
>> >> list on Mars 13 that I think covers most pros and cons of the
>> >> different approaches.
>> >>
>> >> While your suggestion does indeed separate the transaction from the
>> >> proof of payment, it also assumes that the token is held in the wallet
>> >> that pays. Otherwise you would need to keep it in another safe place,
>> >> remember it's reusable. Where would that be? How would you transfer
>> >> that token to your friend?
>> >>
>> >> Thank you again for your comments. I appreciate it.
>> >>
>> >> Best regards,
>> >> Kalle
>> >>
>> >> > --
>> >> > Pieter
>> >> >

2023-06-07 15:36:58

- reply

📅 Original date posted:2015-06-16
📝 Original message:Thank you for the clarification Tom!
/Kalle
2015-06-16 16:05 GMT+02:00 Tom Harding <tomh at thinlink.com>:
> On 6/16/2015 5:12 AM, Kalle Rosenbaum wrote:
>> 2015-06-16 7:26 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>>> Kalle goes to some trouble to describe how merchants need to ensure that
>>> they only accept a PoP provided as a response to their challenge.
>>>
>> Do you mean that it will be hard to explain to merchants that they
>> must check the nonce in the PoP so that it matches the nonce in the
>> pop request?
>
> Sorry for the idiomatic language. No, I just meant that you have
> thought it out in detail! You standardize a latent capability of the
> cryptosystem. It seems very powerful for some classes of users.
>
>

2023-06-07 15:36:57

- reply

📅 Original date posted:2015-06-16
📝 Original message:Another thing worth mentioning is that an SPV wallet cannot validate a
PoP without fetching the input transactions of the PoP from an
external (not bitcoin network) source, for example chain.com or some
other trusted full node's API.
The validation of the PoP depends on the external source(s) being
honest. It can make a valid pop look invalid, but it cannot make an
invalid pop look valid.
/Kalle
2015-06-16 14:12 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
> 2015-06-16 7:26 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>>
>> Kalle goes to some trouble to describe how merchants need to ensure that
>> they only accept a PoP provided as a response to their challenge.
>>
>
> Do you mean that it will be hard to explain to merchants that they
> must check the nonce in the PoP so that it matches the nonce in the
> pop request? I think not, this is a commonly used pattern that anyone
> should be able to grasp. Anyway, merchants will probably use a library
> (though yet non-existing) for PoP, that will hide the gory details. I
> also think that payment providers may want to add PoP to their
> offering to customers (merchants).
>
> Regards,
> /Kalle
>
>>
>>
>> On 6/15/2015 3:00 AM, Pieter Wuille wrote:
>>
>> I did misunderstand that. That changes things significantly.
>>
>> However, having paid is not the same as having had access to the input
>> coins. What about shared wallets or coinjoin?
>>
>> Also, if I understand correctly, there is no commitment to anything you're
>> trying to say about the sender? So once I obtain a proof-of-payment from you
>> about something you paid, I can go claim that it's mine?
>>
>> Why does anyone care who paid? This is like walking into a coffeshop,
>> noticing I don't have money with me, let me friend pay for me, and then have
>> the shop insist that I can't drink it because I'm not the buyer.
>>
>> Track payments, don't try to assign identities to payers.
>>
>> On Jun 15, 2015 11:35 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>>
>>> Hi Pieter!
>>>
>>> It is intended to be a proof that you *have paid* for something. Not
>>> that you have the intent to pay for something. You cannot use PoP
>>> without a transaction to prove.
>>>
>>> So, yes, it's just a proof of access to certain coins that you no longer
>>> have.
>>>
>>> Maybe I don't understand you correctly?
>>>
>>> /Kalle
>>>
>>> 2015-06-15 11:27 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>>> > Now that you have removed the outputs, I don't think it's even a intent
>>> > of
>>> > payment, but just a proof of access to certain coins.
>>> >
>>> > On Jun 15, 2015 11:24 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>> >>
>>> >> Hi all!
>>> >>
>>> >> I have made the discussed changes and updated my implementation
>>> >> (https://github.com/kallerosenbaum/poppoc) accordingly. These are the
>>> >> changes:
>>> >>
>>> >> * There is now only one output, the "pop output", of value 0.
>>> >> * The sequence number of all inputs of the PoP must be set to 0. I
>>> >> chose to set it to 0 for all inputs for simplicity.
>>> >> * The lock_time of the PoP must be set to 499999999 (max block height
>>> >> lock
>>> >> time).
>>> >>
>>> >> The comments so far has been mainly positive or neutral. Are there any
>>> >> major objections against any of the two proposals? If not, I will ask
>>> >> Gregory Maxwell to assign them BIP numbers.
>>> >>
>>> >> The two BIP proposals can be found at
>>> >> https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
>>> >> https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP. The
>>> >> source
>>> >> for the Proof of Payment BIP proposal is also in-lined below.
>>> >>
>>> >> A number of alternative names have been proposed:
>>> >>
>>> >> * Proof of Potential
>>> >> * Proof of Control
>>> >> * Proof of Signature
>>> >> * Signatory Proof
>>> >> * Popo: Proof of payment origin
>>> >> * Pots: Proof of transaction signer
>>> >> * proof of transaction intent
>>> >> * Declaration of intent
>>> >> * Asset-access-and-action-affirmation, AAaAA, or A5
>>> >> * VeriBit
>>> >> * CertiBTC
>>> >> * VBit
>>> >> * PayID
>>> >>
>>> >> Given this list, I still think "Proof of Payment" is the most
>>> >> descriptive
>>> >> to non-technical people.
>>> >>
>>> >> Regards,
>>> >> Kalle
>>> >>
>>> >>
>>> >> #################################################
>>> >> <pre>
>>> >> BIP: <BIP number>
>>> >> Title: Proof of Payment
>>> >> Author: Kalle Rosenbaum <kalle at rosenbaum.se>
>>> >> Status: Draft
>>> >> Type: Standards Track
>>> >> Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
>>> >> </pre>
>>> >>
>>> >> == Abstract ==
>>> >>
>>> >> This BIP describes how a wallet can prove to a server that it has the
>>> >> ability to sign a certain transaction.
>>> >>
>>> >> == Motivation ==
>>> >>
>>> >> There are several scenarios in which it would be useful to prove that
>>> >> you
>>> >> have paid for something. For example:
>>> >>
>>> >> * A pre-paid hotel room where your PoP functions as a key to the door.
>>> >> * An online video rental service where you pay for a video and watch it
>>> >> on
>>> >> any device.
>>> >> * An ad-sign where you pay in advance for e.g. 2 weeks exclusivity.
>>> >> During
>>> >> this period you can upload new content to the sign whenever you like
>>> >> using
>>> >> PoP.
>>> >> * Log in to a pay site using a PoP.
>>> >> * A parking lot you pay for monthly and the car authenticates itself
>>> >> using
>>> >> PoP.
>>> >> * A lottery where all participants pay to the same address, and the
>>> >> winner
>>> >> is selected among the transactions to that address. You exchange the
>>> >> prize
>>> >> for a PoP for the winning transaction.
>>> >>
>>> >> With Proof of Payment, these use cases can be achieved without any
>>> >> personal information (user name, password, e-mail address, etc) being
>>> >> involved.
>>> >>
>>> >> == Rationale ==
>>> >>
>>> >> Desirable properties:
>>> >>
>>> >> # A PoP should be generated on demand.
>>> >> # It should only be usable once to avoid issues due to theft.
>>> >> # It should be able to create a PoP for any payment, regardless of
>>> >> script
>>> >> type (P2SH, P2PKH, etc.).
>>> >> # It should prove that you have enough credentials to unlock all the
>>> >> inputs of the proven transaction.
>>> >> # It should be easy to implement by wallets and servers to ease
>>> >> adoption.
>>> >>
>>> >> Current methods of proving a payment:
>>> >>
>>> >> * In BIP0070, the PaymentRequest together with the transactions
>>> >> fulfilling
>>> >> the request makes some sort of proof. However, it does not meet 1, 2 or
>>> >> 4
>>> >> and it obviously only meets 3 if the payment is made through BIP0070.
>>> >> Also,
>>> >> there's no standard way to request/provide the proof. If standardized
>>> >> it
>>> >> would probably meet 5.
>>> >> * Signing messages, chosen by the server, with the private keys used to
>>> >> sign the transaction. This could meet 1 and 2 but probably not 3. This
>>> >> is
>>> >> not standardized either. 4 Could be met if designed so.
>>> >>
>>> >> If an input script type is P2SH, any satisfying script should do, just
>>> >> as
>>> >> if it was a payment. For M-of-N multisig scripts, that would mean that
>>> >> any
>>> >> set of M keys should be sufficient, not neccesarily the same set of M
>>> >> keys
>>> >> that signed the transaction. This is important because strictly
>>> >> demanding
>>> >> the same set of M keys would defeat the purpose of a multisig address.
>>> >>
>>> >> == Specification ==
>>> >>
>>> >> === Data structure ===
>>> >>
>>> >> A proof of payment for a transaction T, here called PoP(T), is used to
>>> >> prove that one has ownership of the credentials needed to unlock all
>>> >> the
>>> >> inputs of T. It has the exact same structure as a bitcoin transaction
>>> >> with
>>> >> the same inputs as T and in the same order as in T, but with each
>>> >> sequence
>>> >> number set to 0. There is exactly one output, here called the pop
>>> >> output,
>>> >> with value 0. The pop output must have the following format:
>>> >>
>>> >> OP_RETURN <version> <txid> <nonce>
>>> >>
>>> >> {|
>>> >> ! Field !! Size [B] !! Description
>>> >> |-
>>> >> | <version> || 2 || Version, little endian, currently 0x01
>>> >> 0x00
>>> >> |-
>>> >> | <txid> || 32 || The transaction to prove
>>> >> |-
>>> >> | <nonce> || 6 || Random data
>>> >> |}
>>> >>
>>> >> The lock_time of the PoP must be set to 499999999 to prevent the PoP
>>> >> from
>>> >> being included in a block, should it appear on the bitcoin p2p network.
>>> >> This
>>> >> is also the reason for setting the sequence numbers to 0, since
>>> >> sequence
>>> >> number of ffffffff would make lock_time ineffective. This specification
>>> >> demands that all input sequence numbers are 0, not just one of them,
>>> >> which
>>> >> would be sufficient to make lock_time effective. This is for simplicity
>>> >> reasons.
>>> >>
>>> >> An illustration of the PoP data structure and its original payment is
>>> >> shown below.
>>> >>
>>> >> <pre>
>>> >> T
>>> >> +------------------------------------------------+
>>> >> |inputs | outputs |
>>> >> | Value,Sequence | Value,Script |
>>> >> +------------------------------------------------+
>>> >> |input0 1,ffffffff | 0,pay to A |
>>> >> |input1 3,ffffffff | 2,OP_RETURN <some data> |
>>> >> |input2 4,ffffffff | 1,pay to B |
>>> >> | | 4,pay to C |
>>> >> +------------------------------------------------+
>>> >>
>>> >> PoP(T)
>>> >> +-------------------------------------------------------------+
>>> >> | inputs | outputs |
>>> >> | Value,Sequence | Value,Script |
>>> >> +-------------------------------------------------------------+
>>> >> |input0 1,00000000 | 0,OP_RETURN <version> <txid> <nonce> |
>>> >> |input1 3,00000000 | |
>>> >> |input2 4,00000000 | |
>>> >> +-------------------------------------------------------------+
>>> >> | lock_time=499999999 |
>>> >> +-------------------------------------------------------------+
>>> >> </pre>
>>> >>
>>> >> The PoP is signed using the same signing process that is used for
>>> >> bitcoin
>>> >> transactions.
>>> >>
>>> >> The purpose of the nonce is to make it harder to use a stolen PoP; Once
>>> >> the PoP has reached the server, that PoP is useless since the server
>>> >> will
>>> >> generate a new nonce for every PoP request.
>>> >>
>>> >> === Process ===
>>> >>
>>> >> # A proof of payment request is sent from the server to the wallet. The
>>> >> PoP request contains:
>>> >> ## a random nonce
>>> >> ## a destination where to send the PoP, for example a https URL
>>> >> ## data hinting the wallet which transaction to create a proof for. For
>>> >> example:
>>> >> ##* txid, if known by the server
>>> >> ##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
>>> >> payment)
>>> >> ##* amount, label, message or other information from a BIP0021 URI
>>> >> # The wallet identifies a transaction T, if possible. Otherwise it asks
>>> >> the user to select among the ones that match the hints in 1.iii.
>>> >> # The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
>>> >> sign it.
>>> >> # The user confirms
>>> >> # The UPoP(T) is signed by the wallet, creating PoP(T).
>>> >> # The PoP is sent to the destination in 1.ii.
>>> >> # The server receiving the PoP validates it and responds with “valid”
>>> >> or
>>> >> “invalid”.
>>> >> # The wallet displays the response in some way to the user.
>>> >>
>>> >> '''Remarks:'''
>>> >>
>>> >> * The method of transferring the PoP request at step 1 is not specified
>>> >> here. Instead that is specified in separate specifications. See [btcpop
>>> >> scheme BIP](btcpop scheme BIP).
>>> >> * The nonce must be randomly generated by the server for every new PoP
>>> >> request.
>>> >>
>>> >> === Validating a PoP ===
>>> >>
>>> >> The server needs to validate the PoP and reply with "valid" or
>>> >> "invalid".
>>> >> That process is outlined below. If any step fails, the validation is
>>> >> aborted
>>> >> and "invalid" is returned:
>>> >>
>>> >> # Check the format of the PoP. It must pass normal transaction checks,
>>> >> except that the inputs may already be spent.
>>> >> # Check that lock_time is 499999999.
>>> >> # Check that there is exactly one output. This output must have value 0
>>> >> and conform to the OP_RETURN output format outlined above.
>>> >> # Check that the nonce is the same as the one requested.
>>> >> # Check that the inputs of the PoP are exactly the same as in
>>> >> transaction
>>> >> T, except that the sequence numbers must all be 0. The ordering of the
>>> >> inputs must also be the same as in T.
>>> >> # Run the scripts of all the inputs. All scipts must return true.
>>> >> # Check that the txid in the PoP output is the transaction you actually
>>> >> want proof for. If you don’t know exactly what transaction you want
>>> >> proof
>>> >> for, check that the transaction actually pays for the product/service
>>> >> you
>>> >> deliver.
>>> >> # Return "valid".
>>> >>
>>> >> == Security considerations ==
>>> >>
>>> >> * Someone can intercept the PoP-request and change any parameter in it.
>>> >> These can be mitigated by using secure connections. For example:
>>> >> ** Pop destination - Stealing your PoP.
>>> >> ** label - Trick you to sign an unintended pop or set a label that your
>>> >> wallet doesn't have any record for, resulting in a broken service.
>>> >> Always
>>> >> check the PoP before signing.
>>> >> ** nonce - Your pop will not validate on server.
>>> >> * Someone can steal a PoP, for example by tampering with the PoP
>>> >> request,
>>> >> and try to use the service hoping to get a matching nonce. Probability
>>> >> per
>>> >> try: 1/(2^48). The server should have a mechanism for detecting a brute
>>> >> force attack of this kind, or at least slow down the process by
>>> >> delaying the
>>> >> PoP request by some 100 ms or so.
>>> >> * Even if a wallet has no funds it might still be valuable as a
>>> >> generator
>>> >> for PoPs. This makes it important to keep the security of the wallet
>>> >> after
>>> >> it has been emptied.
>>> >> * Transaction malleability may cause the server to have another
>>> >> transaction id for a payment than the client's wallet. In that case the
>>> >> wallet will not be able to prove the transaction to the server. Wallets
>>> >> should not rely on the transaction id of the outgoing transaction.
>>> >> Instead
>>> >> it should listen for the transaction on the network and put that in its
>>> >> list
>>> >> of transactions.
>>> >>
>>> >> == Reference implementation ==
>>> >>
>>> >> [https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
>>> >>
>>> >> [https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
>>> >>
>>> >> == References ==
>>> >>
>>> >> [https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki
>>> >> BIP0021]:
>>> >> URI Scheme
>>> >>
>>> >> [https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki
>>> >> BIP0070]:
>>> >> Payment Protocol
>>> >>
>>> >> [[btcpop scheme BIP]]
>>> >>
>>> >> #########################################################
>>> >>
>>> >> 2015-06-06 23:25 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>>> >> > Thank you all for the feedback.
>>> >> >
>>> >> > I will change the data structure as follows:
>>> >> >
>>> >> > * There will be only one output, the "pop output", and no outputs
>>> >> > from
>>> >> > T will be copied to the PoP.
>>> >> > * The pop output will have value 0.
>>> >> > * The sequence number of all inputs of the PoP will be set to 0. I
>>> >> > chose to set it to 0 for all inputs for simplicity.
>>> >> > * The lock_time of the PoP is always set to 499999999.
>>> >> >
>>> >> > Any comments on this?
>>> >> >
>>> >> > /Kalle
>>> >> >
>>> >> > 2015-06-06 19:00 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>>> >> >> 2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>>> >> >>> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se>
>>> >> >>> wrote:
>>> >> >>>
>>> >> >>>> I'm open to changes here.
>>> >> >>>
>>> >> >>> I suggest:
>>> >> >>>
>>> >> >>> - Don't include any real outputs. They are redundant because the
>>> >> >>> txid is
>>> >> >>> already referenced.
>>> >> >>
>>> >> >> with the nLocktime solution, the copied outputs are not needed.
>>> >> >>
>>> >> >>>
>>> >> >>> - Start the proof script, which should be invalid, with a magic
>>> >> >>> constant and
>>> >> >>> include space for future expansion. This makes PoP's easy to
>>> >> >>> identify
>>> >> >>> and
>>> >> >>> extend.
>>> >> >>
>>> >> >> I did remore the constant (a "PoP" literal ascii encoded string)
>>> >> >> because it didn't add much. The recipient will expect a pop, so it
>>> >> >> will simply treat it as one. I did add a 2 byte version field to
>>> >> >> make
>>> >> >> it extendable.
>>> >> >>
>>> >> >>>
>>> >> >>> - "Proof of Potential"
>>> >> >>
>>> >> >> Noted :-)
>>> >> >>
>>> >> >> Thank you
>>> >> >> /Kalle
>>> >>
>>> >>
>>> >>
>>> >> ------------------------------------------------------------------------------
>>> >>
>>> >> _______________________________________________
>>> >> Bitcoin-development mailing list
>>> >> Bitcoin-development at lists.sourceforge.net
>>> >> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>>> >>
>>> >
>>
>>
>>
>> ------------------------------------------------------------------------------
>>
>>
>>
>> _______________________________________________
>> Bitcoin-development mailing list
>> Bitcoin-development at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>>
>>
>>
>> ------------------------------------------------------------------------------
>>
>> _______________________________________________
>> Bitcoin-development mailing list
>> Bitcoin-development at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>>

2023-06-07 15:36:56

- reply

📅 Original date posted:2015-06-16
📝 Original message:2015-06-16 7:26 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>
> Kalle goes to some trouble to describe how merchants need to ensure that
> they only accept a PoP provided as a response to their challenge.
>
Do you mean that it will be hard to explain to merchants that they
must check the nonce in the PoP so that it matches the nonce in the
pop request? I think not, this is a commonly used pattern that anyone
should be able to grasp. Anyway, merchants will probably use a library
(though yet non-existing) for PoP, that will hide the gory details. I
also think that payment providers may want to add PoP to their
offering to customers (merchants).
Regards,
/Kalle
>
>
> On 6/15/2015 3:00 AM, Pieter Wuille wrote:
>
> I did misunderstand that. That changes things significantly.
>
> However, having paid is not the same as having had access to the input
> coins. What about shared wallets or coinjoin?
>
> Also, if I understand correctly, there is no commitment to anything you're
> trying to say about the sender? So once I obtain a proof-of-payment from you
> about something you paid, I can go claim that it's mine?
>
> Why does anyone care who paid? This is like walking into a coffeshop,
> noticing I don't have money with me, let me friend pay for me, and then have
> the shop insist that I can't drink it because I'm not the buyer.
>
> Track payments, don't try to assign identities to payers.
>
> On Jun 15, 2015 11:35 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>
>> Hi Pieter!
>>
>> It is intended to be a proof that you *have paid* for something. Not
>> that you have the intent to pay for something. You cannot use PoP
>> without a transaction to prove.
>>
>> So, yes, it's just a proof of access to certain coins that you no longer
>> have.
>>
>> Maybe I don't understand you correctly?
>>
>> /Kalle
>>
>> 2015-06-15 11:27 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>> > Now that you have removed the outputs, I don't think it's even a intent
>> > of
>> > payment, but just a proof of access to certain coins.
>> >
>> > On Jun 15, 2015 11:24 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>> >>
>> >> Hi all!
>> >>
>> >> I have made the discussed changes and updated my implementation
>> >> (https://github.com/kallerosenbaum/poppoc) accordingly. These are the
>> >> changes:
>> >>
>> >> * There is now only one output, the "pop output", of value 0.
>> >> * The sequence number of all inputs of the PoP must be set to 0. I
>> >> chose to set it to 0 for all inputs for simplicity.
>> >> * The lock_time of the PoP must be set to 499999999 (max block height
>> >> lock
>> >> time).
>> >>
>> >> The comments so far has been mainly positive or neutral. Are there any
>> >> major objections against any of the two proposals? If not, I will ask
>> >> Gregory Maxwell to assign them BIP numbers.
>> >>
>> >> The two BIP proposals can be found at
>> >> https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
>> >> https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP. The
>> >> source
>> >> for the Proof of Payment BIP proposal is also in-lined below.
>> >>
>> >> A number of alternative names have been proposed:
>> >>
>> >> * Proof of Potential
>> >> * Proof of Control
>> >> * Proof of Signature
>> >> * Signatory Proof
>> >> * Popo: Proof of payment origin
>> >> * Pots: Proof of transaction signer
>> >> * proof of transaction intent
>> >> * Declaration of intent
>> >> * Asset-access-and-action-affirmation, AAaAA, or A5
>> >> * VeriBit
>> >> * CertiBTC
>> >> * VBit
>> >> * PayID
>> >>
>> >> Given this list, I still think "Proof of Payment" is the most
>> >> descriptive
>> >> to non-technical people.
>> >>
>> >> Regards,
>> >> Kalle
>> >>
>> >>
>> >> #################################################
>> >> <pre>
>> >> BIP: <BIP number>
>> >> Title: Proof of Payment
>> >> Author: Kalle Rosenbaum <kalle at rosenbaum.se>
>> >> Status: Draft
>> >> Type: Standards Track
>> >> Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
>> >> </pre>
>> >>
>> >> == Abstract ==
>> >>
>> >> This BIP describes how a wallet can prove to a server that it has the
>> >> ability to sign a certain transaction.
>> >>
>> >> == Motivation ==
>> >>
>> >> There are several scenarios in which it would be useful to prove that
>> >> you
>> >> have paid for something. For example:
>> >>
>> >> * A pre-paid hotel room where your PoP functions as a key to the door.
>> >> * An online video rental service where you pay for a video and watch it
>> >> on
>> >> any device.
>> >> * An ad-sign where you pay in advance for e.g. 2 weeks exclusivity.
>> >> During
>> >> this period you can upload new content to the sign whenever you like
>> >> using
>> >> PoP.
>> >> * Log in to a pay site using a PoP.
>> >> * A parking lot you pay for monthly and the car authenticates itself
>> >> using
>> >> PoP.
>> >> * A lottery where all participants pay to the same address, and the
>> >> winner
>> >> is selected among the transactions to that address. You exchange the
>> >> prize
>> >> for a PoP for the winning transaction.
>> >>
>> >> With Proof of Payment, these use cases can be achieved without any
>> >> personal information (user name, password, e-mail address, etc) being
>> >> involved.
>> >>
>> >> == Rationale ==
>> >>
>> >> Desirable properties:
>> >>
>> >> # A PoP should be generated on demand.
>> >> # It should only be usable once to avoid issues due to theft.
>> >> # It should be able to create a PoP for any payment, regardless of
>> >> script
>> >> type (P2SH, P2PKH, etc.).
>> >> # It should prove that you have enough credentials to unlock all the
>> >> inputs of the proven transaction.
>> >> # It should be easy to implement by wallets and servers to ease
>> >> adoption.
>> >>
>> >> Current methods of proving a payment:
>> >>
>> >> * In BIP0070, the PaymentRequest together with the transactions
>> >> fulfilling
>> >> the request makes some sort of proof. However, it does not meet 1, 2 or
>> >> 4
>> >> and it obviously only meets 3 if the payment is made through BIP0070.
>> >> Also,
>> >> there's no standard way to request/provide the proof. If standardized
>> >> it
>> >> would probably meet 5.
>> >> * Signing messages, chosen by the server, with the private keys used to
>> >> sign the transaction. This could meet 1 and 2 but probably not 3. This
>> >> is
>> >> not standardized either. 4 Could be met if designed so.
>> >>
>> >> If an input script type is P2SH, any satisfying script should do, just
>> >> as
>> >> if it was a payment. For M-of-N multisig scripts, that would mean that
>> >> any
>> >> set of M keys should be sufficient, not neccesarily the same set of M
>> >> keys
>> >> that signed the transaction. This is important because strictly
>> >> demanding
>> >> the same set of M keys would defeat the purpose of a multisig address.
>> >>
>> >> == Specification ==
>> >>
>> >> === Data structure ===
>> >>
>> >> A proof of payment for a transaction T, here called PoP(T), is used to
>> >> prove that one has ownership of the credentials needed to unlock all
>> >> the
>> >> inputs of T. It has the exact same structure as a bitcoin transaction
>> >> with
>> >> the same inputs as T and in the same order as in T, but with each
>> >> sequence
>> >> number set to 0. There is exactly one output, here called the pop
>> >> output,
>> >> with value 0. The pop output must have the following format:
>> >>
>> >> OP_RETURN <version> <txid> <nonce>
>> >>
>> >> {|
>> >> ! Field !! Size [B] !! Description
>> >> |-
>> >> | <version> || 2 || Version, little endian, currently 0x01
>> >> 0x00
>> >> |-
>> >> | <txid> || 32 || The transaction to prove
>> >> |-
>> >> | <nonce> || 6 || Random data
>> >> |}
>> >>
>> >> The lock_time of the PoP must be set to 499999999 to prevent the PoP
>> >> from
>> >> being included in a block, should it appear on the bitcoin p2p network.
>> >> This
>> >> is also the reason for setting the sequence numbers to 0, since
>> >> sequence
>> >> number of ffffffff would make lock_time ineffective. This specification
>> >> demands that all input sequence numbers are 0, not just one of them,
>> >> which
>> >> would be sufficient to make lock_time effective. This is for simplicity
>> >> reasons.
>> >>
>> >> An illustration of the PoP data structure and its original payment is
>> >> shown below.
>> >>
>> >> <pre>
>> >> T
>> >> +------------------------------------------------+
>> >> |inputs | outputs |
>> >> | Value,Sequence | Value,Script |
>> >> +------------------------------------------------+
>> >> |input0 1,ffffffff | 0,pay to A |
>> >> |input1 3,ffffffff | 2,OP_RETURN <some data> |
>> >> |input2 4,ffffffff | 1,pay to B |
>> >> | | 4,pay to C |
>> >> +------------------------------------------------+
>> >>
>> >> PoP(T)
>> >> +-------------------------------------------------------------+
>> >> | inputs | outputs |
>> >> | Value,Sequence | Value,Script |
>> >> +-------------------------------------------------------------+
>> >> |input0 1,00000000 | 0,OP_RETURN <version> <txid> <nonce> |
>> >> |input1 3,00000000 | |
>> >> |input2 4,00000000 | |
>> >> +-------------------------------------------------------------+
>> >> | lock_time=499999999 |
>> >> +-------------------------------------------------------------+
>> >> </pre>
>> >>
>> >> The PoP is signed using the same signing process that is used for
>> >> bitcoin
>> >> transactions.
>> >>
>> >> The purpose of the nonce is to make it harder to use a stolen PoP; Once
>> >> the PoP has reached the server, that PoP is useless since the server
>> >> will
>> >> generate a new nonce for every PoP request.
>> >>
>> >> === Process ===
>> >>
>> >> # A proof of payment request is sent from the server to the wallet. The
>> >> PoP request contains:
>> >> ## a random nonce
>> >> ## a destination where to send the PoP, for example a https URL
>> >> ## data hinting the wallet which transaction to create a proof for. For
>> >> example:
>> >> ##* txid, if known by the server
>> >> ##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
>> >> payment)
>> >> ##* amount, label, message or other information from a BIP0021 URI
>> >> # The wallet identifies a transaction T, if possible. Otherwise it asks
>> >> the user to select among the ones that match the hints in 1.iii.
>> >> # The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
>> >> sign it.
>> >> # The user confirms
>> >> # The UPoP(T) is signed by the wallet, creating PoP(T).
>> >> # The PoP is sent to the destination in 1.ii.
>> >> # The server receiving the PoP validates it and responds with “valid”
>> >> or
>> >> “invalid”.
>> >> # The wallet displays the response in some way to the user.
>> >>
>> >> '''Remarks:'''
>> >>
>> >> * The method of transferring the PoP request at step 1 is not specified
>> >> here. Instead that is specified in separate specifications. See [btcpop
>> >> scheme BIP](btcpop scheme BIP).
>> >> * The nonce must be randomly generated by the server for every new PoP
>> >> request.
>> >>
>> >> === Validating a PoP ===
>> >>
>> >> The server needs to validate the PoP and reply with "valid" or
>> >> "invalid".
>> >> That process is outlined below. If any step fails, the validation is
>> >> aborted
>> >> and "invalid" is returned:
>> >>
>> >> # Check the format of the PoP. It must pass normal transaction checks,
>> >> except that the inputs may already be spent.
>> >> # Check that lock_time is 499999999.
>> >> # Check that there is exactly one output. This output must have value 0
>> >> and conform to the OP_RETURN output format outlined above.
>> >> # Check that the nonce is the same as the one requested.
>> >> # Check that the inputs of the PoP are exactly the same as in
>> >> transaction
>> >> T, except that the sequence numbers must all be 0. The ordering of the
>> >> inputs must also be the same as in T.
>> >> # Run the scripts of all the inputs. All scipts must return true.
>> >> # Check that the txid in the PoP output is the transaction you actually
>> >> want proof for. If you don’t know exactly what transaction you want
>> >> proof
>> >> for, check that the transaction actually pays for the product/service
>> >> you
>> >> deliver.
>> >> # Return "valid".
>> >>
>> >> == Security considerations ==
>> >>
>> >> * Someone can intercept the PoP-request and change any parameter in it.
>> >> These can be mitigated by using secure connections. For example:
>> >> ** Pop destination - Stealing your PoP.
>> >> ** label - Trick you to sign an unintended pop or set a label that your
>> >> wallet doesn't have any record for, resulting in a broken service.
>> >> Always
>> >> check the PoP before signing.
>> >> ** nonce - Your pop will not validate on server.
>> >> * Someone can steal a PoP, for example by tampering with the PoP
>> >> request,
>> >> and try to use the service hoping to get a matching nonce. Probability
>> >> per
>> >> try: 1/(2^48). The server should have a mechanism for detecting a brute
>> >> force attack of this kind, or at least slow down the process by
>> >> delaying the
>> >> PoP request by some 100 ms or so.
>> >> * Even if a wallet has no funds it might still be valuable as a
>> >> generator
>> >> for PoPs. This makes it important to keep the security of the wallet
>> >> after
>> >> it has been emptied.
>> >> * Transaction malleability may cause the server to have another
>> >> transaction id for a payment than the client's wallet. In that case the
>> >> wallet will not be able to prove the transaction to the server. Wallets
>> >> should not rely on the transaction id of the outgoing transaction.
>> >> Instead
>> >> it should listen for the transaction on the network and put that in its
>> >> list
>> >> of transactions.
>> >>
>> >> == Reference implementation ==
>> >>
>> >> [https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
>> >>
>> >> [https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
>> >>
>> >> == References ==
>> >>
>> >> [https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki
>> >> BIP0021]:
>> >> URI Scheme
>> >>
>> >> [https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki
>> >> BIP0070]:
>> >> Payment Protocol
>> >>
>> >> [[btcpop scheme BIP]]
>> >>
>> >> #########################################################
>> >>
>> >> 2015-06-06 23:25 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>> >> > Thank you all for the feedback.
>> >> >
>> >> > I will change the data structure as follows:
>> >> >
>> >> > * There will be only one output, the "pop output", and no outputs
>> >> > from
>> >> > T will be copied to the PoP.
>> >> > * The pop output will have value 0.
>> >> > * The sequence number of all inputs of the PoP will be set to 0. I
>> >> > chose to set it to 0 for all inputs for simplicity.
>> >> > * The lock_time of the PoP is always set to 499999999.
>> >> >
>> >> > Any comments on this?
>> >> >
>> >> > /Kalle
>> >> >
>> >> > 2015-06-06 19:00 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>> >> >> 2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>> >> >>> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se>
>> >> >>> wrote:
>> >> >>>
>> >> >>>> I'm open to changes here.
>> >> >>>
>> >> >>> I suggest:
>> >> >>>
>> >> >>> - Don't include any real outputs. They are redundant because the
>> >> >>> txid is
>> >> >>> already referenced.
>> >> >>
>> >> >> with the nLocktime solution, the copied outputs are not needed.
>> >> >>
>> >> >>>
>> >> >>> - Start the proof script, which should be invalid, with a magic
>> >> >>> constant and
>> >> >>> include space for future expansion. This makes PoP's easy to
>> >> >>> identify
>> >> >>> and
>> >> >>> extend.
>> >> >>
>> >> >> I did remore the constant (a "PoP" literal ascii encoded string)
>> >> >> because it didn't add much. The recipient will expect a pop, so it
>> >> >> will simply treat it as one. I did add a 2 byte version field to
>> >> >> make
>> >> >> it extendable.
>> >> >>
>> >> >>>
>> >> >>> - "Proof of Potential"
>> >> >>
>> >> >> Noted :-)
>> >> >>
>> >> >> Thank you
>> >> >> /Kalle
>> >>
>> >>
>> >>
>> >> ------------------------------------------------------------------------------
>> >>
>> >> _______________________________________________
>> >> Bitcoin-development mailing list
>> >> Bitcoin-development at lists.sourceforge.net
>> >> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>> >>
>> >
>
>
>
> ------------------------------------------------------------------------------
>
>
>
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>
>
>
> ------------------------------------------------------------------------------
>
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>

2023-06-07 15:36:54

- reply

📅 Original date posted:2015-06-16
📝 Original message:Thank you for your comments Pieter! Please find my answers below.
2015-06-16 16:31 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
> On Mon, Jun 15, 2015 at 1:59 PM, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>>
>> 2015-06-15 12:00 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>> I'm not sure if we will be able to support PoP with CoinJoin. Maybe
>> someone with more insight into CoinJoin have some input?
>
>
> Not really. The problem is that you assume a transaction corresponds to a
> single payment. This is true for simple wallet use cases, but not compatible
> with CoinJoin, or with systems that for example would want to combine
> multiple payments in a single transaction.
>
Yes, you are right. It's not compatible with CoinJoin and the likes.
>
> 48 bits seems low to me, but it does indeed solve the problem. Why not 128
> or 256 bits?
The nonce is limited because of the OP_RETURN output being limited to
40 bytes of data: 2 bytes version, 32 bytes txid, 6 bytes nonce.
>
>> > Why does anyone care who paid? This is like walking into a coffeshop,
>> > noticing I don't have money with me, let me friend pay for me, and then
>> > have
>> > the shop insist that I can't drink it because I'm not the buyer.
>>
>> If you pay as you use the service (ie pay for coffee upfront), there's
>> no need for PoP. Please see the Motivation section. But you are right
>> that you must have the wallet(s) that paid at hand when you issue a
>> PoP.
>>
>> >
>> > Track payments, don't try to assign identities to payers.
>>
>> Please elaborate, I don't understand what you mean here.
>
>
> I think that is a mistake. You should not assume that the wallet who held
> the coins is the payer/buyer. That's what I said earlier; you're implicitly
> creating an identity (the one who holds these keys) based on the
> transaction. This seems fundamentally wrong to me, and not necessary. The
> receiver should not care who paid or how, he should care what was payed for.
You are saying that it's a problem that the wallet used to pay, must
also be used to issue the PoP? That may very well be a problem in some
cases. People using PoP should of course be aware of it's limitations
and act accordingly, i.e. don't pay for concert tickets for a friend
and expect your friend to be able to enter the arena with her wallet.
As Tom Harding noted, it is possible to transfer keys to your friend's
wallet, but that might not be desirable if those keys are also used
for other payments. Also that would weaken the security of an HD
wallet, since a chain code along with a private key would reveal all
keys in that tree. Another solution is that your friend forwards the
PoP request to your wallet, through twitter or SMS, and you send the
PoP for her. Maybe that forwarding mechanism can be built into wallets
and automated so that the wallet automatically suggests to sign the
PoP for your friend. This is probably something to investigate
further, but not within the scope of this BIP.
Of course the simplest solution would be to send money to your friend
first so that she can pay for the ticket from her own wallet, but
that's not always feasible.
>
> The easiest solution to this IMHO would be an extension to the payment
> protocol that gives you (or your wallet) a token in return for paying, and
> that knowledge of that token is used to gain access to the services you
> provide.
>
That token would then be reusable. Someone stealing it would be able
to use it as much as she wants. That is what I want to avoid with PoP.
The BIP proposal briefly mentions something like this in the
rationale. I also had a discussion about this with Mike Hearn on this
list on Mars 13 that I think covers most pros and cons of the
different approaches.
While your suggestion does indeed separate the transaction from the
proof of payment, it also assumes that the token is held in the wallet
that pays. Otherwise you would need to keep it in another safe place,
remember it's reusable. Where would that be? How would you transfer
that token to your friend?
Thank you again for your comments. I appreciate it.
Best regards,
Kalle
> --
> Pieter
>

2023-06-07 15:36:53

- reply

📅 Original date posted:2015-06-15
📝 Original message:2015-06-15 12:00 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
> I did misunderstand that. That changes things significantly.
>
> However, having paid is not the same as having had access to the input
> coins. What about shared wallets or coinjoin?
Wallets will have the same ability to make PoPs as they have in making
payments, see my motivation and rationale sections. CoinJoin is not
compatible with PoP, Luke-Jr brought that up a week ago:
"This appears to be incompatible with CoinJoin at least. Maybe there's some
clean way to avoid that by using
https://github.com/Blockstream/contracthashtool ?"
I'm not sure if we will be able to support PoP with CoinJoin. Maybe
someone with more insight into CoinJoin have some input?
>
> Also, if I understand correctly, there is no commitment to anything you're
> trying to say about the sender? So once I obtain a proof-of-payment from you
> about something you paid, I can go claim that it's mine?
I don't understand this. The pop includes a nonce randomly generated
by the server. If you're very lucky, 1/(2^48) per try, you can reuse a
pop.
>
> Why does anyone care who paid? This is like walking into a coffeshop,
> noticing I don't have money with me, let me friend pay for me, and then have
> the shop insist that I can't drink it because I'm not the buyer.
If you pay as you use the service (ie pay for coffee upfront), there's
no need for PoP. Please see the Motivation section. But you are right
that you must have the wallet(s) that paid at hand when you issue a
PoP.
>
> Track payments, don't try to assign identities to payers.
Please elaborate, I don't understand what you mean here.
Regards,
Kalle
>
> On Jun 15, 2015 11:35 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>
>> Hi Pieter!
>>
>> It is intended to be a proof that you *have paid* for something. Not
>> that you have the intent to pay for something. You cannot use PoP
>> without a transaction to prove.
>>
>> So, yes, it's just a proof of access to certain coins that you no longer
>> have.
>>
>> Maybe I don't understand you correctly?
>>
>> /Kalle
>>
>> 2015-06-15 11:27 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>> > Now that you have removed the outputs, I don't think it's even a intent
>> > of
>> > payment, but just a proof of access to certain coins.
>> >
>> > On Jun 15, 2015 11:24 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>> >>
>> >> Hi all!
>> >>
>> >> I have made the discussed changes and updated my implementation
>> >> (https://github.com/kallerosenbaum/poppoc) accordingly. These are the
>> >> changes:
>> >>
>> >> * There is now only one output, the "pop output", of value 0.
>> >> * The sequence number of all inputs of the PoP must be set to 0. I
>> >> chose to set it to 0 for all inputs for simplicity.
>> >> * The lock_time of the PoP must be set to 499999999 (max block height
>> >> lock
>> >> time).
>> >>
>> >> The comments so far has been mainly positive or neutral. Are there any
>> >> major objections against any of the two proposals? If not, I will ask
>> >> Gregory Maxwell to assign them BIP numbers.
>> >>
>> >> The two BIP proposals can be found at
>> >> https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
>> >> https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP. The
>> >> source
>> >> for the Proof of Payment BIP proposal is also in-lined below.
>> >>
>> >> A number of alternative names have been proposed:
>> >>
>> >> * Proof of Potential
>> >> * Proof of Control
>> >> * Proof of Signature
>> >> * Signatory Proof
>> >> * Popo: Proof of payment origin
>> >> * Pots: Proof of transaction signer
>> >> * proof of transaction intent
>> >> * Declaration of intent
>> >> * Asset-access-and-action-affirmation, AAaAA, or A5
>> >> * VeriBit
>> >> * CertiBTC
>> >> * VBit
>> >> * PayID
>> >>
>> >> Given this list, I still think "Proof of Payment" is the most
>> >> descriptive
>> >> to non-technical people.
>> >>
>> >> Regards,
>> >> Kalle
>> >>
>> >>
>> >> #################################################
>> >> <pre>
>> >> BIP: <BIP number>
>> >> Title: Proof of Payment
>> >> Author: Kalle Rosenbaum <kalle at rosenbaum.se>
>> >> Status: Draft
>> >> Type: Standards Track
>> >> Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
>> >> </pre>
>> >>
>> >> == Abstract ==
>> >>
>> >> This BIP describes how a wallet can prove to a server that it has the
>> >> ability to sign a certain transaction.
>> >>
>> >> == Motivation ==
>> >>
>> >> There are several scenarios in which it would be useful to prove that
>> >> you
>> >> have paid for something. For example:
>> >>
>> >> * A pre-paid hotel room where your PoP functions as a key to the door.
>> >> * An online video rental service where you pay for a video and watch it
>> >> on
>> >> any device.
>> >> * An ad-sign where you pay in advance for e.g. 2 weeks exclusivity.
>> >> During
>> >> this period you can upload new content to the sign whenever you like
>> >> using
>> >> PoP.
>> >> * Log in to a pay site using a PoP.
>> >> * A parking lot you pay for monthly and the car authenticates itself
>> >> using
>> >> PoP.
>> >> * A lottery where all participants pay to the same address, and the
>> >> winner
>> >> is selected among the transactions to that address. You exchange the
>> >> prize
>> >> for a PoP for the winning transaction.
>> >>
>> >> With Proof of Payment, these use cases can be achieved without any
>> >> personal information (user name, password, e-mail address, etc) being
>> >> involved.
>> >>
>> >> == Rationale ==
>> >>
>> >> Desirable properties:
>> >>
>> >> # A PoP should be generated on demand.
>> >> # It should only be usable once to avoid issues due to theft.
>> >> # It should be able to create a PoP for any payment, regardless of
>> >> script
>> >> type (P2SH, P2PKH, etc.).
>> >> # It should prove that you have enough credentials to unlock all the
>> >> inputs of the proven transaction.
>> >> # It should be easy to implement by wallets and servers to ease
>> >> adoption.
>> >>
>> >> Current methods of proving a payment:
>> >>
>> >> * In BIP0070, the PaymentRequest together with the transactions
>> >> fulfilling
>> >> the request makes some sort of proof. However, it does not meet 1, 2 or
>> >> 4
>> >> and it obviously only meets 3 if the payment is made through BIP0070.
>> >> Also,
>> >> there's no standard way to request/provide the proof. If standardized
>> >> it
>> >> would probably meet 5.
>> >> * Signing messages, chosen by the server, with the private keys used to
>> >> sign the transaction. This could meet 1 and 2 but probably not 3. This
>> >> is
>> >> not standardized either. 4 Could be met if designed so.
>> >>
>> >> If an input script type is P2SH, any satisfying script should do, just
>> >> as
>> >> if it was a payment. For M-of-N multisig scripts, that would mean that
>> >> any
>> >> set of M keys should be sufficient, not neccesarily the same set of M
>> >> keys
>> >> that signed the transaction. This is important because strictly
>> >> demanding
>> >> the same set of M keys would defeat the purpose of a multisig address.
>> >>
>> >> == Specification ==
>> >>
>> >> === Data structure ===
>> >>
>> >> A proof of payment for a transaction T, here called PoP(T), is used to
>> >> prove that one has ownership of the credentials needed to unlock all
>> >> the
>> >> inputs of T. It has the exact same structure as a bitcoin transaction
>> >> with
>> >> the same inputs as T and in the same order as in T, but with each
>> >> sequence
>> >> number set to 0. There is exactly one output, here called the pop
>> >> output,
>> >> with value 0. The pop output must have the following format:
>> >>
>> >> OP_RETURN <version> <txid> <nonce>
>> >>
>> >> {|
>> >> ! Field !! Size [B] !! Description
>> >> |-
>> >> | <version> || 2 || Version, little endian, currently 0x01
>> >> 0x00
>> >> |-
>> >> | <txid> || 32 || The transaction to prove
>> >> |-
>> >> | <nonce> || 6 || Random data
>> >> |}
>> >>
>> >> The lock_time of the PoP must be set to 499999999 to prevent the PoP
>> >> from
>> >> being included in a block, should it appear on the bitcoin p2p network.
>> >> This
>> >> is also the reason for setting the sequence numbers to 0, since
>> >> sequence
>> >> number of ffffffff would make lock_time ineffective. This specification
>> >> demands that all input sequence numbers are 0, not just one of them,
>> >> which
>> >> would be sufficient to make lock_time effective. This is for simplicity
>> >> reasons.
>> >>
>> >> An illustration of the PoP data structure and its original payment is
>> >> shown below.
>> >>
>> >> <pre>
>> >> T
>> >> +------------------------------------------------+
>> >> |inputs | outputs |
>> >> | Value,Sequence | Value,Script |
>> >> +------------------------------------------------+
>> >> |input0 1,ffffffff | 0,pay to A |
>> >> |input1 3,ffffffff | 2,OP_RETURN <some data> |
>> >> |input2 4,ffffffff | 1,pay to B |
>> >> | | 4,pay to C |
>> >> +------------------------------------------------+
>> >>
>> >> PoP(T)
>> >> +-------------------------------------------------------------+
>> >> | inputs | outputs |
>> >> | Value,Sequence | Value,Script |
>> >> +-------------------------------------------------------------+
>> >> |input0 1,00000000 | 0,OP_RETURN <version> <txid> <nonce> |
>> >> |input1 3,00000000 | |
>> >> |input2 4,00000000 | |
>> >> +-------------------------------------------------------------+
>> >> | lock_time=499999999 |
>> >> +-------------------------------------------------------------+
>> >> </pre>
>> >>
>> >> The PoP is signed using the same signing process that is used for
>> >> bitcoin
>> >> transactions.
>> >>
>> >> The purpose of the nonce is to make it harder to use a stolen PoP; Once
>> >> the PoP has reached the server, that PoP is useless since the server
>> >> will
>> >> generate a new nonce for every PoP request.
>> >>
>> >> === Process ===
>> >>
>> >> # A proof of payment request is sent from the server to the wallet. The
>> >> PoP request contains:
>> >> ## a random nonce
>> >> ## a destination where to send the PoP, for example a https URL
>> >> ## data hinting the wallet which transaction to create a proof for. For
>> >> example:
>> >> ##* txid, if known by the server
>> >> ##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
>> >> payment)
>> >> ##* amount, label, message or other information from a BIP0021 URI
>> >> # The wallet identifies a transaction T, if possible. Otherwise it asks
>> >> the user to select among the ones that match the hints in 1.iii.
>> >> # The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
>> >> sign it.
>> >> # The user confirms
>> >> # The UPoP(T) is signed by the wallet, creating PoP(T).
>> >> # The PoP is sent to the destination in 1.ii.
>> >> # The server receiving the PoP validates it and responds with “valid”
>> >> or
>> >> “invalid”.
>> >> # The wallet displays the response in some way to the user.
>> >>
>> >> '''Remarks:'''
>> >>
>> >> * The method of transferring the PoP request at step 1 is not specified
>> >> here. Instead that is specified in separate specifications. See [btcpop
>> >> scheme BIP](btcpop scheme BIP).
>> >> * The nonce must be randomly generated by the server for every new PoP
>> >> request.
>> >>
>> >> === Validating a PoP ===
>> >>
>> >> The server needs to validate the PoP and reply with "valid" or
>> >> "invalid".
>> >> That process is outlined below. If any step fails, the validation is
>> >> aborted
>> >> and "invalid" is returned:
>> >>
>> >> # Check the format of the PoP. It must pass normal transaction checks,
>> >> except that the inputs may already be spent.
>> >> # Check that lock_time is 499999999.
>> >> # Check that there is exactly one output. This output must have value 0
>> >> and conform to the OP_RETURN output format outlined above.
>> >> # Check that the nonce is the same as the one requested.
>> >> # Check that the inputs of the PoP are exactly the same as in
>> >> transaction
>> >> T, except that the sequence numbers must all be 0. The ordering of the
>> >> inputs must also be the same as in T.
>> >> # Run the scripts of all the inputs. All scipts must return true.
>> >> # Check that the txid in the PoP output is the transaction you actually
>> >> want proof for. If you don’t know exactly what transaction you want
>> >> proof
>> >> for, check that the transaction actually pays for the product/service
>> >> you
>> >> deliver.
>> >> # Return "valid".
>> >>
>> >> == Security considerations ==
>> >>
>> >> * Someone can intercept the PoP-request and change any parameter in it.
>> >> These can be mitigated by using secure connections. For example:
>> >> ** Pop destination - Stealing your PoP.
>> >> ** label - Trick you to sign an unintended pop or set a label that your
>> >> wallet doesn't have any record for, resulting in a broken service.
>> >> Always
>> >> check the PoP before signing.
>> >> ** nonce - Your pop will not validate on server.
>> >> * Someone can steal a PoP, for example by tampering with the PoP
>> >> request,
>> >> and try to use the service hoping to get a matching nonce. Probability
>> >> per
>> >> try: 1/(2^48). The server should have a mechanism for detecting a brute
>> >> force attack of this kind, or at least slow down the process by
>> >> delaying the
>> >> PoP request by some 100 ms or so.
>> >> * Even if a wallet has no funds it might still be valuable as a
>> >> generator
>> >> for PoPs. This makes it important to keep the security of the wallet
>> >> after
>> >> it has been emptied.
>> >> * Transaction malleability may cause the server to have another
>> >> transaction id for a payment than the client's wallet. In that case the
>> >> wallet will not be able to prove the transaction to the server. Wallets
>> >> should not rely on the transaction id of the outgoing transaction.
>> >> Instead
>> >> it should listen for the transaction on the network and put that in its
>> >> list
>> >> of transactions.
>> >>
>> >> == Reference implementation ==
>> >>
>> >> [https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
>> >>
>> >> [https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
>> >>
>> >> == References ==
>> >>
>> >> [https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki
>> >> BIP0021]:
>> >> URI Scheme
>> >>
>> >> [https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki
>> >> BIP0070]:
>> >> Payment Protocol
>> >>
>> >> [[btcpop scheme BIP]]
>> >>
>> >> #########################################################
>> >>
>> >> 2015-06-06 23:25 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>> >> > Thank you all for the feedback.
>> >> >
>> >> > I will change the data structure as follows:
>> >> >
>> >> > * There will be only one output, the "pop output", and no outputs
>> >> > from
>> >> > T will be copied to the PoP.
>> >> > * The pop output will have value 0.
>> >> > * The sequence number of all inputs of the PoP will be set to 0. I
>> >> > chose to set it to 0 for all inputs for simplicity.
>> >> > * The lock_time of the PoP is always set to 499999999.
>> >> >
>> >> > Any comments on this?
>> >> >
>> >> > /Kalle
>> >> >
>> >> > 2015-06-06 19:00 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>> >> >> 2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>> >> >>> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se>
>> >> >>> wrote:
>> >> >>>
>> >> >>>> I'm open to changes here.
>> >> >>>
>> >> >>> I suggest:
>> >> >>>
>> >> >>> - Don't include any real outputs. They are redundant because the
>> >> >>> txid is
>> >> >>> already referenced.
>> >> >>
>> >> >> with the nLocktime solution, the copied outputs are not needed.
>> >> >>
>> >> >>>
>> >> >>> - Start the proof script, which should be invalid, with a magic
>> >> >>> constant and
>> >> >>> include space for future expansion. This makes PoP's easy to
>> >> >>> identify
>> >> >>> and
>> >> >>> extend.
>> >> >>
>> >> >> I did remore the constant (a "PoP" literal ascii encoded string)
>> >> >> because it didn't add much. The recipient will expect a pop, so it
>> >> >> will simply treat it as one. I did add a 2 byte version field to
>> >> >> make
>> >> >> it extendable.
>> >> >>
>> >> >>>
>> >> >>> - "Proof of Potential"
>> >> >>
>> >> >> Noted :-)
>> >> >>
>> >> >> Thank you
>> >> >> /Kalle
>> >>
>> >>
>> >>
>> >> ------------------------------------------------------------------------------
>> >>
>> >> _______________________________________________
>> >> Bitcoin-development mailing list
>> >> Bitcoin-development at lists.sourceforge.net
>> >> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>> >>
>> >

2023-06-07 15:36:52

- reply

📅 Original date posted:2015-06-06
📝 Original message:2015-06-06 17:32 GMT+02:00 Peter Todd <pete at petertodd.org>:
> On Sat, Jun 06, 2015 at 05:23:48PM +0200, Pieter Wuille wrote:
>> On Sat, Jun 6, 2015 at 5:18 PM, Luke Dashjr <luke at dashjr.org> wrote:
>>
>> > I also agree with Pieter, that this should *not* be so cleanly compatible
>> > with Bitcoin transactions. If you wish to share code, perhaps using an
>> > invalid opcode rather than OP_RETURN would be appropriate.
>>
>>
>> Using an invalid opcode would merely send funds into the void. It wouldn't
>> invalidate the transaction.
>
> Just set nLockTime to 500000000-1 and nSequence appropriately to make
> the transaction impossible to mine for the next 9500 years.
Actually, I suggested that on this list on april 27, but shortly after
rejected my own idea:
#######################
"Or a really high lock_time, but it would not make it invalid, just delayed."
Ok, this was a bad idea, since nodes would have to keep it in memory.
Please disregard that idea...
########################
Now I think I rejected it on based on a misunderstanding. Nodes will
not put them in their mempool unless it's value is near in time,
right? From the 0.9.0 release notes: "Accept nLockTime transactions
that finalize in the next block".
In that case this is a really nice option.
>
> Though I agree that this whole idea seems a bit dubious to me.
>
> --
> 'peter'[:-1]@petertodd.org
> 00000000000000000000dd919214b66444dcebb4aa0214c1ab7c8b3b633be71f
>
> ------------------------------------------------------------------------------
>
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>

2023-06-07 15:36:50

- reply

📅 Original date posted:2015-06-15
📝 Original message:Hi all!
I have made the discussed changes and updated my implementation (
https://github.com/kallerosenbaum/poppoc) accordingly. These are the
changes:
* There is now only one output, the "pop output", of value 0.
* The sequence number of all inputs of the PoP must be set to 0. I
chose to set it to 0 for all inputs for simplicity.
* The lock_time of the PoP must be set to 499999999 (max block height lock
time).
The comments so far has been mainly positive or neutral. Are there any
major objections against any of the two proposals? If not, I will ask
Gregory Maxwell to assign them BIP numbers.
The two BIP proposals can be found at
https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP. The source
for the Proof of Payment BIP proposal is also in-lined below.
A number of alternative names have been proposed:
* Proof of Potential
* Proof of Control
* Proof of Signature
* Signatory Proof
* Popo: Proof of payment origin
* Pots: Proof of transaction signer
* proof of transaction intent
* Declaration of intent
* Asset-access-and-action-affirmation, AAaAA, or A5
* VeriBit
* CertiBTC
* VBit
* PayID
Given this list, I still think "Proof of Payment" is the most descriptive
to non-technical people.
Regards,
Kalle
#################################################
<pre>
BIP: <BIP number>
Title: Proof of Payment
Author: Kalle Rosenbaum <kalle at rosenbaum.se>
Status: Draft
Type: Standards Track
Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
</pre>
== Abstract ==
This BIP describes how a wallet can prove to a server that it has the
ability to sign a certain transaction.
== Motivation ==
There are several scenarios in which it would be useful to prove that you
have paid for something. For example:
* A pre-paid hotel room where your PoP functions as a key to the door.
* An online video rental service where you pay for a video and watch it on
any device.
* An ad-sign where you pay in advance for e.g. 2 weeks exclusivity. During
this period you can upload new content to the sign whenever you like using
PoP.
* Log in to a pay site using a PoP.
* A parking lot you pay for monthly and the car authenticates itself using
PoP.
* A lottery where all participants pay to the same address, and the winner
is selected among the transactions to that address. You exchange the prize
for a PoP for the winning transaction.
With Proof of Payment, these use cases can be achieved without any personal
information (user name, password, e-mail address, etc) being involved.
== Rationale ==
Desirable properties:
# A PoP should be generated on demand.
# It should only be usable once to avoid issues due to theft.
# It should be able to create a PoP for any payment, regardless of script
type (P2SH, P2PKH, etc.).
# It should prove that you have enough credentials to unlock all the inputs
of the proven transaction.
# It should be easy to implement by wallets and servers to ease adoption.
Current methods of proving a payment:
* In BIP0070, the PaymentRequest together with the transactions fulfilling
the request makes some sort of proof. However, it does not meet 1, 2 or 4
and it obviously only meets 3 if the payment is made through BIP0070. Also,
there's no standard way to request/provide the proof. If standardized it
would probably meet 5.
* Signing messages, chosen by the server, with the private keys used to
sign the transaction. This could meet 1 and 2 but probably not 3. This is
not standardized either. 4 Could be met if designed so.
If an input script type is P2SH, any satisfying script should do, just as
if it was a payment. For M-of-N multisig scripts, that would mean that any
set of M keys should be sufficient, not neccesarily the same set of M keys
that signed the transaction. This is important because strictly demanding
the same set of M keys would defeat the purpose of a multisig address.
== Specification ==
=== Data structure ===
A proof of payment for a transaction T, here called PoP(T), is used to
prove that one has ownership of the credentials needed to unlock all the
inputs of T. It has the exact same structure as a bitcoin transaction with
the same inputs as T and in the same order as in T, but with each sequence
number set to 0. There is exactly one output, here called the pop output,
with value 0. The pop output must have the following format:
OP_RETURN <version> <txid> <nonce>
{|
! Field !! Size [B] !! Description
|-
| <version> || 2 || Version, little endian, currently 0x01 0x00
|-
| <txid> || 32 || The transaction to prove
|-
| <nonce> || 6 || Random data
|}
The lock_time of the PoP must be set to 499999999 to prevent the PoP from
being included in a block, should it appear on the bitcoin p2p network.
This is also the reason for setting the sequence numbers to 0, since
sequence number of ffffffff would make lock_time ineffective. This
specification demands that all input sequence numbers are 0, not just one
of them, which would be sufficient to make lock_time effective. This is for
simplicity reasons.
An illustration of the PoP data structure and its original payment is shown
below.
<pre>
T
+------------------------------------------------+
|inputs | outputs |
| Value,Sequence | Value,Script |
+------------------------------------------------+
|input0 1,ffffffff | 0,pay to A |
|input1 3,ffffffff | 2,OP_RETURN <some data> |
|input2 4,ffffffff | 1,pay to B |
| | 4,pay to C |
+------------------------------------------------+
PoP(T)
+-------------------------------------------------------------+
| inputs | outputs |
| Value,Sequence | Value,Script |
+-------------------------------------------------------------+
|input0 1,00000000 | 0,OP_RETURN <version> <txid> <nonce> |
|input1 3,00000000 | |
|input2 4,00000000 | |
+-------------------------------------------------------------+
| lock_time=499999999 |
+-------------------------------------------------------------+
</pre>
The PoP is signed using the same signing process that is used for bitcoin
transactions.
The purpose of the nonce is to make it harder to use a stolen PoP; Once the
PoP has reached the server, that PoP is useless since the server will
generate a new nonce for every PoP request.
=== Process ===
# A proof of payment request is sent from the server to the wallet. The PoP
request contains:
## a random nonce
## a destination where to send the PoP, for example a https URL
## data hinting the wallet which transaction to create a proof for. For
example:
##* txid, if known by the server
##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
payment)
##* amount, label, message or other information from a BIP0021 URI
# The wallet identifies a transaction T, if possible. Otherwise it asks the
user to select among the ones that match the hints in 1.iii.
# The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
sign it.
# The user confirms
# The UPoP(T) is signed by the wallet, creating PoP(T).
# The PoP is sent to the destination in 1.ii.
# The server receiving the PoP validates it and responds with “valid” or
“invalid”.
# The wallet displays the response in some way to the user.
'''Remarks:'''
* The method of transferring the PoP request at step 1 is not specified
here. Instead that is specified in separate specifications. See [btcpop
scheme BIP](btcpop scheme BIP).
* The nonce must be randomly generated by the server for every new PoP
request.
=== Validating a PoP ===
The server needs to validate the PoP and reply with "valid" or "invalid".
That process is outlined below. If any step fails, the validation is
aborted and "invalid" is returned:
# Check the format of the PoP. It must pass normal transaction checks,
except that the inputs may already be spent.
# Check that lock_time is 499999999.
# Check that there is exactly one output. This output must have value 0 and
conform to the OP_RETURN output format outlined above.
# Check that the nonce is the same as the one requested.
# Check that the inputs of the PoP are exactly the same as in transaction
T, except that the sequence numbers must all be 0. The ordering of the
inputs must also be the same as in T.
# Run the scripts of all the inputs. All scipts must return true.
# Check that the txid in the PoP output is the transaction you actually
want proof for. If you don’t know exactly what transaction you want proof
for, check that the transaction actually pays for the product/service you
deliver.
# Return "valid".
== Security considerations ==
* Someone can intercept the PoP-request and change any parameter in it.
These can be mitigated by using secure connections. For example:
** Pop destination - Stealing your PoP.
** label - Trick you to sign an unintended pop or set a label that your
wallet doesn't have any record for, resulting in a broken service. Always
check the PoP before signing.
** nonce - Your pop will not validate on server.
* Someone can steal a PoP, for example by tampering with the PoP request,
and try to use the service hoping to get a matching nonce. Probability per
try: 1/(2^48). The server should have a mechanism for detecting a brute
force attack of this kind, or at least slow down the process by delaying
the PoP request by some 100 ms or so.
* Even if a wallet has no funds it might still be valuable as a generator
for PoPs. This makes it important to keep the security of the wallet after
it has been emptied.
* Transaction malleability may cause the server to have another transaction
id for a payment than the client's wallet. In that case the wallet will not
be able to prove the transaction to the server. Wallets should not rely on
the transaction id of the outgoing transaction. Instead it should listen
for the transaction on the network and put that in its list of transactions.
== Reference implementation ==
[https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
[https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
== References ==
[https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki BIP0021]:
URI Scheme
[https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki BIP0070]:
Payment Protocol
[[btcpop scheme BIP]]
#########################################################
2015-06-06 23:25 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
> Thank you all for the feedback.
>
> I will change the data structure as follows:
>
> * There will be only one output, the "pop output", and no outputs from
> T will be copied to the PoP.
> * The pop output will have value 0.
> * The sequence number of all inputs of the PoP will be set to 0. I
> chose to set it to 0 for all inputs for simplicity.
> * The lock_time of the PoP is always set to 499999999.
>
> Any comments on this?
>
> /Kalle
>
> 2015-06-06 19:00 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>> 2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>>> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>>
>>>> I'm open to changes here.
>>>
>>> I suggest:
>>>
>>> - Don't include any real outputs. They are redundant because the txid
is
>>> already referenced.
>>
>> with the nLocktime solution, the copied outputs are not needed.
>>
>>>
>>> - Start the proof script, which should be invalid, with a magic
constant and
>>> include space for future expansion. This makes PoP's easy to identify
and
>>> extend.
>>
>> I did remore the constant (a "PoP" literal ascii encoded string)
>> because it didn't add much. The recipient will expect a pop, so it
>> will simply treat it as one. I did add a 2 byte version field to make
>> it extendable.
>>
>>>
>>> - "Proof of Potential"
>>
>> Noted :-)
>>
>> Thank you
>> /Kalle
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2023-06-07 15:36:50

- reply

📅 Original date posted:2015-06-06
📝 Original message:Thank you all for the feedback.
I will change the data structure as follows:
* There will be only one output, the "pop output", and no outputs from
T will be copied to the PoP.
* The pop output will have value 0.
* The sequence number of all inputs of the PoP will be set to 0. I
chose to set it to 0 for all inputs for simplicity.
* The lock_time of the PoP is always set to 499999999.
Any comments on this?
/Kalle
2015-06-06 19:00 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
> 2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>
>>> I'm open to changes here.
>>
>> I suggest:
>>
>> - Don't include any real outputs. They are redundant because the txid is
>> already referenced.
>
> with the nLocktime solution, the copied outputs are not needed.
>
>>
>> - Start the proof script, which should be invalid, with a magic constant and
>> include space for future expansion. This makes PoP's easy to identify and
>> extend.
>
> I did remore the constant (a "PoP" literal ascii encoded string)
> because it didn't add much. The recipient will expect a pop, so it
> will simply treat it as one. I did add a 2 byte version field to make
> it extendable.
>
>>
>> - "Proof of Potential"
>
> Noted :-)
>
> Thank you
> /Kalle

2023-06-07 15:36:50

- reply

📅 Original date posted:2015-06-06
📝 Original message:2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>
>> I'm open to changes here.
>
> I suggest:
>
> - Don't include any real outputs. They are redundant because the txid is
> already referenced.
with the nLocktime solution, the copied outputs are not needed.
>
> - Start the proof script, which should be invalid, with a magic constant and
> include space for future expansion. This makes PoP's easy to identify and
> extend.
I did remore the constant (a "PoP" literal ascii encoded string)
because it didn't add much. The recipient will expect a pop, so it
will simply treat it as one. I did add a 2 byte version field to make
it extendable.
>
> - "Proof of Potential"
Noted :-)
Thank you
/Kalle

2023-06-07 15:36:49

- reply

📅 Original date posted:2015-06-06
📝 Original message:>> The idea is to simplify implementation. Existing software can be used
>> as is to sign and validate PoPs. But I do agree that it would be a
>> cleaner specification if we would make the PoP invalid as a
>> transaction. I'm open to changes here. I do like the idea to prepend a
>> constant string. But that would require changes in transaction signing
>> and validation code, wouldn't it?
>
>
> Yes, of course. An alternative is adding a 21M BTC output at the end, or
> bitflipping the txin prevout hashes, or another reversible transformation on
> the transaction data that is guaranteed to invalidate it.
If we do decide to make Pops invalid as transactions, there are a lot
of ways to do that. I guess the main question is if we should make
Pops invalid as transactions or not. So far I prefer to keep them
valid for the above reason.
>
> I think that the risk of asking people to sign something that is not an
> actual transaction, but could be used as one, is very scary.
>
I would feel comfortable doing it. It's just a matter of trusting your
wallet, which you already do with your ordinary transactions.
>>
>> > Also, I would call it "proof of transaction intent", as it's a
>> > commitment to
>> > a transaction and proof of its validity, but not a proof that an actual
>> > transaction took place, nor a means to prevent it from being double
>> > spent.
>>
>>
>> Naming is hard. I think a simpler name that explains what its main
>> purpose is (prove that you paid for something) is better than a name
>> that exactly tries to explain what it is.
>
>
> "Proof of Payment" indeed does make me think it's something that proves you
> paid. But as described, that is not what a PoP does. It proves the ability
> to create a particular transaction, and committing to it. There is no actual
> payment involved (plus, payment makes me think you're talking about BIP70
> payments, not simple Bitcoin transactions).
>
>>
>> "Proof of transaction
>> intent" does not help me understand what this is about. But I would
>> like to see more name suggestions. The name does not prevent people
>> from using it for other purposes, ie internet over telephone network.
>
>
> I don't understand why something like "Proof of Transaction Intent" would be
> incompatible with internet over telephone network either...
>
No, I meant that it's ok to call it Proof of Payment even though
people may use it for other stuff.
> --
> Pieter
>

2023-06-07 15:36:48

- reply

📅 Original date posted:2015-06-06
📝 Original message:> What do you gain by making PoPs actually valid transactions? You could for
> example change the signature hashing algorithm (prepend a constant string,
> or add a second hashing step) for signing, rendering the signatures in a PoP
> unusable for actual transaction, while still committing to the same actual
> transaction. That would also remove the need for the OP_RETURN to catch
> fees.
The idea is to simplify implementation. Existing software can be used
as is to sign and validate PoPs. But I do agree that it would be a
cleaner specification if we would make the PoP invalid as a
transaction. I'm open to changes here. I do like the idea to prepend a
constant string. But that would require changes in transaction signing
and validation code, wouldn't it?
>
> Also, I would call it "proof of transaction intent", as it's a commitment to
> a transaction and proof of its validity, but not a proof that an actual
> transaction took place, nor a means to prevent it from being double spent.
>
Naming is hard. I think a simpler name that explains what its main
purpose is (prove that you paid for something) is better than a name
that exactly tries to explain what it is. "Proof of transaction
intent" does not help me understand what this is about. But I would
like to see more name suggestions. The name does not prevent people
from using it for other purposes, ie internet over telephone network.
Thank you
/Kalle
>
>
> On Sat, Jun 6, 2015 at 4:35 PM, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>>
>> Hi
>>
>> Following earlier posts on Proof of Payment I'm now proposing the
>> following BIP (To read it formatted instead, go to
>> https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP).
>>
>> Regards,
>> Kalle Rosenbaum
>>
>> <pre>
>> BIP: <BIP number>
>> Title: Proof of Payment
>> Author: Kalle Rosenbaum <kalle at rosenbaum.se>
>> Status: Draft
>> Type: Standards Track
>> Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
>> </pre>
>>
>> == Abstract ==
>>
>> This BIP describes how a wallet can prove to a server that it has the
>> ability to sign a certain transaction.
>>
>> == Motivation ==
>>
>> There are several scenarios in which it would be useful to prove that you
>> have paid for something. For example:
>>
>> * A pre-paid hotel room where your PoP functions as a key to the door.
>> * An online video rental service where you pay for a video and watch it on
>> any device.
>> * An ad-sign where you pay in advance for e.g. 2 weeks exclusivity. During
>> this period you can upload new content to the sign whenever you like using
>> PoP.
>> * Log in to a pay site using a PoP.
>> * A parking lot you pay for monthly and the car authenticates itself using
>> PoP.
>> * A lottery where all participants pay to the same address, and the winner
>> is selected among the transactions to that address. You exchange the prize
>> for a PoP for the winning transaction.
>>
>> With Proof of Payment, these use cases can be achieved without any
>> personal information (user name, password, e-mail address, etc) being
>> involved.
>>
>> == Rationale ==
>>
>> Desirable properties:
>>
>> # A PoP should be generated on demand.
>> # It should only be usable once to avoid issues due to theft.
>> # It should be able to create a PoP for any payment, regardless of script
>> type (P2SH, P2PKH, etc.).
>> # It should prove that you have enough credentials to unlock all the
>> inputs of the proven transaction.
>> # It should be easy to implement by wallets and servers to ease adoption.
>>
>> Current methods of proving a payment:
>>
>> * In BIP0070, the PaymentRequest together with the transactions fulfilling
>> the request makes some sort of proof. However, it does not meet 1, 2 or 4
>> and it obviously only meets 3 if the payment is made through BIP0070. Also,
>> there's no standard way to request/provide the proof. If standardized it
>> would probably meet 5.
>> * Signing messages, chosen by the server, with the private keys used to
>> sign the transaction. This could meet 1 and 2 but probably not 3. This is
>> not standardized either. 4 Could be met if designed so.
>>
>> If the script type is P2SH, any satisfying script should do, just like for
>> a payment. For M-of-N multisig scripts, that would mean that any set of M
>> keys should be sufficient, not neccesarily the same set of M keys that
>> signed the transaction. This is important because strictly demanding the
>> same set of M keys would undermine the purpose of a multisig address.
>>
>> == Specification ==
>>
>> === Data structure ===
>>
>> A proof of payment for a transaction T, here called PoP(T), is used to
>> prove that one has ownership of the credentials needed to unlock all the
>> inputs of T. It has the exact same structure as a bitcoin transaction with
>> the same inputs and outputs as T and in the same order as in T. There is
>> also one OP_RETURN output inserted at index 0, here called the pop output.
>> This output must have the following format:
>>
>> OP_RETURN <version> <txid> <nonce>
>>
>> {|
>> ! Field !! Size [B] !! Description
>> |-
>> | <version> || 2 || Version, little endian, currently 0x01 0x00
>> |-
>> | <txid> || 32 || The transaction to prove
>> |-
>> | <nonce> || 6 || Random data
>> |}
>>
>> The value of the pop output is set to the same value as the transaction
>> fee of T. Also, if the outputs of T contains an OP_RETURN output, that
>> output must not be included in the PoP because there can only be one
>> OP_RETURN output in a transaction. The value of that OP_RETURN output is
>> instead added to the value of the pop output.
>>
>> An illustration of the PoP data structure and its original payment is
>> shown below.
>>
>> <pre>
>> T
>> +----------------------------------------------+
>> |inputs | outputs |
>> | Value | Value Script |
>> +----------------------------------------------+
>> |input0 1 | 0 pay to A |
>> |input1 3 | 2 OP_RETURN <some data> |
>> |input2 4 | 1 pay to B |
>> | | 4 pay to C |
>> +----------------------------------------------+
>>
>> PoP(T)
>> +----------------------------------------------------------+
>> |inputs | outputs |
>> | Value | Value Script |
>> +----------------------------------------------------------+
>> |input0 1 | 3 OP_RETURN <version> <txid> <nonce> |
>> |input1 3 | 0 pay to A |
>> |input2 4 | 1 pay to B |
>> | | 4 pay to C |
>> +----------------------------------------------------------+
>> </pre>
>>
>> The PoP is signed using the same signing process that is used for bitcoin
>> transactions.
>>
>> The purpose of the nonce is to make it harder to use a stolen PoP; Once
>> the PoP has reached the server, that PoP is useless since the server will
>> generate a new nonce for every PoP request.
>>
>> Since a PoP is indistinguishable from a bitcoin transaction, there is a
>> risk that it, accidently or maliciously, enters the bitcoin p2p network. If
>> T is still unconfirmed, or if a reorg takes place, chances are that PoP(T)
>> ends up in a block, invalidating T. Therefore it is important that the
>> outputs of the PoP are the same as in T. The zero transaction fee in PoP(T)
>> is to minimize the incentives for miners to select PoP(T) for inclusion.
>>
>> === Process ===
>>
>> # A proof of payment request is sent from the server to the wallet. The
>> PoP request contains:
>> ## a random nonce
>> ## a destination where to send the PoP, for example a https URL
>> ## data hinting the wallet which transaction to create a proof for. For
>> example:
>> ##* txid, if known by the server
>> ##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
>> payment)
>> ##* amount, label, message or other information from a BIP0021 URL
>> # The wallet identifies a transaction T, if possible. Otherwise it asks
>> the user to select among the ones that match the hints in 1.iii.
>> # The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
>> sign it.
>> # The user confirms
>> # The UPoP(T) is signed by the wallet, creating PoP(T).
>> # The PoP is sent to the destination in 1.ii.
>> # The server receiving the PoP validates it and responds with “valid” or
>> “invalid”.
>> # The wallet displays the response in some way to the user.
>>
>> '''Remarks:'''
>>
>> * The method of transferring the PoP request at step 1 is not specified
>> here. Instead that is specified in separate specifications. See [btcpop
>> scheme BIP](btcpop scheme BIP).
>> * The nonce must be randomly generated by the server for every new PoP
>> request.
>>
>> === Validating a PoP ===
>>
>> The server needs to validate the PoP and reply with "valid" or "invalid".
>> That process is outlined below. If any step fails, the validation is aborted
>> and "invalid" is returned:
>>
>> # Check the format of the PoP. It must pass normal transaction checks,
>> except that the inputs may already be spent.
>> # Check the PoP output at index 0. It must conform to the OP_RETURN output
>> format outlined above.
>> # Check that the rest of the outputs exactly corresponds to the outputs of
>> T and that they appear in the same order as in T. An exception to this is
>> that any OP_RETURN outputs of T must not be included in the PoP. All output
>> value from the OP_RETURN must instead be included in the PoP output.
>> # Check that the nonce is the same as the one you requested.
>> # Check that the inputs of the PoP are exactly the same as in transaction
>> T, and in the same order.
>> # Check the scripts of all the inputs, as would be done on a normal
>> transaction.
>> # Check that the txid in the PoP output is the transaction you actually
>> want proof for. If you don’t know exactly what transaction you want proof
>> for, check that the transaction actually pays for the product/service you
>> deliver.
>> # Return "valid".
>>
>> == Security considerations ==
>>
>> * Someone can intercept the PoP-request and change the PoP destination so
>> that the user sends the PoP to the bad actor.
>> * Someone can intercept the PoP-request and change for example the txid to
>> trick the user to sign a PoP for another transaction than the intended. This
>> can of course be avoided if the user is actually looking at the UPoP before
>> signing it. The bad actor could also set hints for a transaction, existing
>> or not, that the user didn’t make, resulting in a broken service.
>> * Someone can steal a PoP and try to use the service hoping to get a
>> matching nonce. Probability per try: 1/(2^48). The server should have a
>> mechanism for detecting a brute force attack of this kind, or at least slow
>> down the process by delaying the PoP request by some 100 ms or so.
>> * Even if a wallet has no funds it might still be valuable as a generator
>> for PoPs. This makes it important to keep the security of the wallet after
>> it has been emptied.
>> * Transaction malleability may cause the server to have another
>> transaction id than the wallet for the payment. In that case the wallet will
>> not be able to prove the transaction for the server. Wallets should not rely
>> on the transaction id of the outgoing transaction. Instead it should listen
>> for the transaction on the network and put that in its list of transactions.
>>
>> The first two issues are the same attack vector as for traditional, ie
>> BIP0021, bitcoin payments. They could be mitigated by using secure
>> connections.
>>
>> == Reference implementation ==
>>
>> [https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
>>
>> [https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
>>
>> == References ==
>>
>> [https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki BIP0021]:
>> URI Scheme
>>
>> [https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki BIP0070]:
>> Payment Protocol
>>
>> [[btcpop scheme BIP]]
>>
>>
>>
>> ------------------------------------------------------------------------------
>>
>> _______________________________________________
>> Bitcoin-development mailing list
>> Bitcoin-development at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>>
>

2023-06-07 15:36:46

- reply

📅 Original date posted:2015-06-06
📝 Original message:Hi
Following earlier posts on Proof of Payment I'm now proposing the following
BIP (To read it formatted instead, go to
https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP).
Regards,
Kalle Rosenbaum
<pre>
BIP: <BIP number>
Title: Proof of Payment
Author: Kalle Rosenbaum <kalle at rosenbaum.se>
Status: Draft
Type: Standards Track
Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
</pre>
== Abstract ==
This BIP describes how a wallet can prove to a server that it has the
ability to sign a certain transaction.
== Motivation ==
There are several scenarios in which it would be useful to prove that you
have paid for something. For example:
* A pre-paid hotel room where your PoP functions as a key to the door.
* An online video rental service where you pay for a video and watch it on
any device.
* An ad-sign where you pay in advance for e.g. 2 weeks exclusivity. During
this period you can upload new content to the sign whenever you like using
PoP.
* Log in to a pay site using a PoP.
* A parking lot you pay for monthly and the car authenticates itself using
PoP.
* A lottery where all participants pay to the same address, and the winner
is selected among the transactions to that address. You exchange the prize
for a PoP for the winning transaction.
With Proof of Payment, these use cases can be achieved without any personal
information (user name, password, e-mail address, etc) being involved.
== Rationale ==
Desirable properties:
# A PoP should be generated on demand.
# It should only be usable once to avoid issues due to theft.
# It should be able to create a PoP for any payment, regardless of script
type (P2SH, P2PKH, etc.).
# It should prove that you have enough credentials to unlock all the inputs
of the proven transaction.
# It should be easy to implement by wallets and servers to ease adoption.
Current methods of proving a payment:
* In BIP0070, the PaymentRequest together with the transactions fulfilling
the request makes some sort of proof. However, it does not meet 1, 2 or 4
and it obviously only meets 3 if the payment is made through BIP0070. Also,
there's no standard way to request/provide the proof. If standardized it
would probably meet 5.
* Signing messages, chosen by the server, with the private keys used to
sign the transaction. This could meet 1 and 2 but probably not 3. This is
not standardized either. 4 Could be met if designed so.
If the script type is P2SH, any satisfying script should do, just like for
a payment. For M-of-N multisig scripts, that would mean that any set of M
keys should be sufficient, not neccesarily the same set of M keys that
signed the transaction. This is important because strictly demanding the
same set of M keys would undermine the purpose of a multisig address.
== Specification ==
=== Data structure ===
A proof of payment for a transaction T, here called PoP(T), is used to
prove that one has ownership of the credentials needed to unlock all the
inputs of T. It has the exact same structure as a bitcoin transaction with
the same inputs and outputs as T and in the same order as in T. There is
also one OP_RETURN output inserted at index 0, here called the pop output.
This output must have the following format:
OP_RETURN <version> <txid> <nonce>
{|
! Field !! Size [B] !! Description
|-
| <version> || 2 || Version, little endian, currently 0x01 0x00
|-
| <txid> || 32 || The transaction to prove
|-
| <nonce> || 6 || Random data
|}
The value of the pop output is set to the same value as the transaction fee
of T. Also, if the outputs of T contains an OP_RETURN output, that output
must not be included in the PoP because there can only be one OP_RETURN
output in a transaction. The value of that OP_RETURN output is instead
added to the value of the pop output.
An illustration of the PoP data structure and its original payment is shown
below.
<pre>
T
+----------------------------------------------+
|inputs | outputs |
| Value | Value Script |
+----------------------------------------------+
|input0 1 | 0 pay to A |
|input1 3 | 2 OP_RETURN <some data> |
|input2 4 | 1 pay to B |
| | 4 pay to C |
+----------------------------------------------+
PoP(T)
+----------------------------------------------------------+
|inputs | outputs |
| Value | Value Script |
+----------------------------------------------------------+
|input0 1 | 3 OP_RETURN <version> <txid> <nonce> |
|input1 3 | 0 pay to A |
|input2 4 | 1 pay to B |
| | 4 pay to C |
+----------------------------------------------------------+
</pre>
The PoP is signed using the same signing process that is used for bitcoin
transactions.
The purpose of the nonce is to make it harder to use a stolen PoP; Once the
PoP has reached the server, that PoP is useless since the server will
generate a new nonce for every PoP request.
Since a PoP is indistinguishable from a bitcoin transaction, there is a
risk that it, accidently or maliciously, enters the bitcoin p2p network. If
T is still unconfirmed, or if a reorg takes place, chances are that PoP(T)
ends up in a block, invalidating T. Therefore it is important that the
outputs of the PoP are the same as in T. The zero transaction fee in PoP(T)
is to minimize the incentives for miners to select PoP(T) for inclusion.
=== Process ===
# A proof of payment request is sent from the server to the wallet. The PoP
request contains:
## a random nonce
## a destination where to send the PoP, for example a https URL
## data hinting the wallet which transaction to create a proof for. For
example:
##* txid, if known by the server
##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
payment)
##* amount, label, message or other information from a BIP0021 URL
# The wallet identifies a transaction T, if possible. Otherwise it asks the
user to select among the ones that match the hints in 1.iii.
# The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
sign it.
# The user confirms
# The UPoP(T) is signed by the wallet, creating PoP(T).
# The PoP is sent to the destination in 1.ii.
# The server receiving the PoP validates it and responds with “valid” or
“invalid”.
# The wallet displays the response in some way to the user.
'''Remarks:'''
* The method of transferring the PoP request at step 1 is not specified
here. Instead that is specified in separate specifications. See [btcpop
scheme BIP](btcpop scheme BIP).
* The nonce must be randomly generated by the server for every new PoP
request.
=== Validating a PoP ===
The server needs to validate the PoP and reply with "valid" or "invalid".
That process is outlined below. If any step fails, the validation is
aborted and "invalid" is returned:
# Check the format of the PoP. It must pass normal transaction checks,
except that the inputs may already be spent.
# Check the PoP output at index 0. It must conform to the OP_RETURN output
format outlined above.
# Check that the rest of the outputs exactly corresponds to the outputs of
T and that they appear in the same order as in T. An exception to this is
that any OP_RETURN outputs of T must not be included in the PoP. All output
value from the OP_RETURN must instead be included in the PoP output.
# Check that the nonce is the same as the one you requested.
# Check that the inputs of the PoP are exactly the same as in transaction
T, and in the same order.
# Check the scripts of all the inputs, as would be done on a normal
transaction.
# Check that the txid in the PoP output is the transaction you actually
want proof for. If you don’t know exactly what transaction you want proof
for, check that the transaction actually pays for the product/service you
deliver.
# Return "valid".
== Security considerations ==
* Someone can intercept the PoP-request and change the PoP destination so
that the user sends the PoP to the bad actor.
* Someone can intercept the PoP-request and change for example the txid to
trick the user to sign a PoP for another transaction than the intended.
This can of course be avoided if the user is actually looking at the UPoP
before signing it. The bad actor could also set hints for a transaction,
existing or not, that the user didn’t make, resulting in a broken service.
* Someone can steal a PoP and try to use the service hoping to get a
matching nonce. Probability per try: 1/(2^48). The server should have a
mechanism for detecting a brute force attack of this kind, or at least slow
down the process by delaying the PoP request by some 100 ms or so.
* Even if a wallet has no funds it might still be valuable as a generator
for PoPs. This makes it important to keep the security of the wallet after
it has been emptied.
* Transaction malleability may cause the server to have another transaction
id than the wallet for the payment. In that case the wallet will not be
able to prove the transaction for the server. Wallets should not rely on
the transaction id of the outgoing transaction. Instead it should listen
for the transaction on the network and put that in its list of transactions.
The first two issues are the same attack vector as for traditional, ie
BIP0021, bitcoin payments. They could be mitigated by using secure
connections.
== Reference implementation ==
[https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
[https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
== References ==
[https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki BIP0021]:
URI Scheme
[https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki BIP0070]:
Payment Protocol
[[btcpop scheme BIP]]
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2023-06-07 15:35:33

- reply

📅 Original date posted:2015-05-24
📝 Original message:Hi all!
As indicated in my first email regarding Proof of Payment (Mars 13, subject
"Proof of Payment"), I would like to BIP it. I have two proposals:
* PoP datastructure and process:
https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment
* btcpop: URI scheme:
https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme
Basically, my question to the community is: Do you agree that these are
BIP-able?
The proposals are not yet BIP formatted, but pretty complete. An
implementation is avaliable at https://github.com/kallerosenbaum/poppoc.
Specifically, the PoP validating code is in PopValidator.java
<https://github.com/kallerosenbaum/poppoc/blob/master/src/main/java/se/rosenbaum/poppoc/core/validate/PopValidator.java>
.
As far as I can tell from the previous thread, no major objection against
the idea was raised. PoP, if standardized, would bring a lot of utility to
bitcoin: Paysite login, concert tickets, left luggage lockers, lotteries,
video rental, etc.
Further on, I'd like to extend BIP70 to support PoP, but that will have to
wait until we have consensus around the two basic proposals above.
I have received some great feedback from the community and included most of
it in the updated version of the specification. The essential changes are:
* If a PoP for some reason appears in the bitcoin p2p network, we must make
sure that IF it is included in a block it should have minimal impact. The
solution I chose was to include all outputs of the original paymet in the
PoP. That way, if the PoP is included it will not alter the payees. (Thanks
to Tom Harding for pointing out the problem and Magnus Andersson for the
initial solution).
* The check if the transaction is actually a tx that you want proof for is
moved to later in the validation process. Otherwise, one could get
information on what transactions pays for which services by simply sending
erroneously signed PoPs with a transaction id we're interested in.
* A version field of 2 bytes is included. Currently the only valid version
is 0x00 0x01. (Thanks Martin Lie)
* The "PoP" literal is removed. It provides little value as the receiver of
a PoP expects a PoP. (Again, thanks Martin Lie for making me think about
this.)
Regards,
Kalle Rosenbaum
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2023-06-07 15:32:43

- reply

📅 Original date posted:2015-04-23
📝 Original message:Hi Martin,
Thank you very much for your comments. See my answers inline:
Den 23 apr 2015 03:28 skrev "Martin Lie" <martin at datamagi.no>:
>
> Hej, Kalle.
>
> I love the idea of standardised PoPs, including a protocol for
requesting/sending them as an extension of BIP-70.
>
Me too!
>
> A couple of comments:
>
> 1. You admit that the txid is just a convenience and not strictly
necessary. Perhaps this should be reflected in the sequence of bits/bytes
in the record you're proposing, e.g. "OP_RETURN POP_LITERAL <nonce> <txid>"?
>
I was thinking that txid should be mandatory just as the nonce so the order
was arbitrarily chosen. I think you may be right that it's more intuitive
to put txid last if it's not mandatory in a future version. It makes sense
to swap order. I'll put that on my todo list.
> 2. Building on #1, perhaps there could be other identifying information
than a txid? Perhaps a txid field shouldn't be "hardcoded" into the
standard at all?
>
> How about taking the same approach as BIP-43 (and others) and use a
prefix that determines how the rest of the records should be interpreted,
i.e. a "type" (or "purpose" or "version" or whatever you'd like to call it)
field. This would allow for different purposes/versions of a PoP, including
as of now unforeseen ones.
>
> The new structure would then be:
> OP_RETURN POP_PREFIX POP_TYPE POP_NONCE POP_PAYLOAD
>
> POP_PREFIX (? bytes): I'll leave it up to you to specify the exact bits
(and length) of the POP_PREFIX, but if your literal is used, it'd be 3
bytes: 0x506f50.
>
> Literals in Bitcoin protocols generally seem to be of the "binary" sort
as opposed to human-readable text, so perhaps the devs wouldn't ACK
something as "wasteful" as using 3 bytes just to identify it as a PoP
record? Obviously, this is a small detail that can be changed at short
notice, but as with all standards - once people start using it, you're
mostly stuck with what you have. ;)
>
Yes, maybe we could drop POP_PREFIX altogether. The server is expecting a
pop and can therefore just assume it's a pop. No need to explicitly write
that inside the pop. Can you think of a scenario where it is actually
needed. Keeping the POP_PREFIX makes sense only if other transaction-like
data structures with OP_RETURN appears in the same contexts as pops. What
do you think?
> POP_TYPE: (1 byte): 0x01 for your "standard" version, which would mean
that the payload contains a txid.
>
This is a good idea. Todo!
> POP_NONCE: (4 bytes): "2^32 re-uses should be enough for everyone", no? ;)
>
Euhm, well, I don't know... The bigger the better. If we drop POP_PREFIX we
could allow for 2 bytes version and 6 bytes nonce. Or 1 byte version and 7
bytes nonce.
> POP_PAYLOAD (32+ bytes): The contents of which is determined by POP_TYPE,
e.g. a txid or possibly extra nonce data. Or perhaps some text that makes
the purpose or context of this PoP human-readable? (This could then be
stored by wallets in order to show a list of what kind of proofs you've
sent.)
>
For now I think I'll stick to "txid is mandatory".
>
> 3. I noticed that your post-OP_RETURN structure included exactly 40
bytes. Is that due to the 40-byte limitation on OP_RETURN's "data"? Are you
aware that it will be increased to 80 bytes? Cf. https://
<https://github.com/bitcoin/bitcoin/pull/5286>github.com
<https://github.com/bitcoin/bitcoin/pull/5286>/
<https://github.com/bitcoin/bitcoin/pull/5286>bitcoin
<https://github.com/bitcoin/bitcoin/pull/5286>/
<https://github.com/bitcoin/bitcoin/pull/5286>bitcoin
<https://github.com/bitcoin/bitcoin/pull/5286>/pull/5286
<https://github.com/bitcoin/bitcoin/pull/5286>
>
Yes, I deliberately limited the data to 40 bytes for that reason. With
versioning, this may change in the future.
> :)
>
>
> Vennlig hilsen
> Martin Lie
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2023-06-07 15:32:42

- reply

📅 Original date posted:2015-04-28
📝 Original message:Hi Jorge,
I don't think I understand the question. Proof of Payment is used to prove
that you have the credentials needed for a certain transaction. It does not
care where in the blockchain the transaction is. Or if it's in the
blockchain at all.
/Kalle
So at the low level, how does a "proof of payment" differ from just proving
that a given transaction is in a given block (what SPV nodes take as proof
of payment today)?
On Apr 27, 2015 2:42 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
> "Or a really high lock_time, but it would not make it invalid, just
> delayed."
>
> Ok, this was a bad idea, since nodes would have to keep it in memory.
> Please disregard that idea...
>
> Kalle
>
> Den 27 apr 2015 14:35 skrev "Kalle Rosenbaum" <kalle at rosenbaum.se>:
> >
> > >
> > > Some more use cases might be:
> > > Waiting in comfort:
> > > - Send a payment ahead of time, then wander over and collect the goods
> > > after X confirmations.
> > >
> > > Authorized pickup :
> > > - Hot wallet software used by related people could facilitate the use
> > > of 1 of N multisig funds. Any one of the N wallets could collect goods
> > > and services purchased by any of the others.
> >
> > I like this one, because it shows the power of reusing the transaction
> data structure.
> >
> > >
> > > Non-monetary gifts:
> > > - Sender exports spent keys to a beneficiary, enabling PoP to work as
> a
> > > gift claim
> > >
> > > Contingent services:
> > > - Without Bob's permission, a 3rd party conditions action on a payment
> > > made from Alice to Bob. For example, if you donated at least .02 BTC
> to
> > > Dorian, you (or combining scenarios, any of your N authorized family
> > > members), can come to my dinner party.
> >
> > This is an interesting one.
> >
> > >
> > > I tried out your demo wallet and service and it worked as advertised.
> > >
> > > Could the same standard also be used to prove that a transaction COULD
> > > BE created? To generalize the concept beyond actual payments, you
> could
> > > call it something like proof of payment potential.
> >
> > I guess it's possible, but we'd have to remove the txid from the output,
> since there is none. This is a way of saying "I'm in control of these
> addresses". The other party/parties can then verify the funds on the
> blockchain and watch those addresses for changes. Maybe there are some
> interesting use cases here. Ideas?
> >
> > >
> > > Why not make these proofs permanently INVALID transactions, to remove
> > > any possibility of their being mined and spending everything to fees
> > > when used in this way, and also in cases involving reorganizations?
> >
> > Yes. Initially I thought it would be enough that the funds are already
> spent, but I think you're right here. Reorgs could be a problem. Worse, you
> also might want to prove 0-confirmation transactions, in which case it's a
> huge security problem. Someone might intercept the PoP and publish it on
> the bitcoin network, spending all the funds. But I still would like wallets
> to be able to build/verify PoPs with little or no modifications. Could we
> possibly change the version number on the PoP to something other than 1?
> Maybe 2^4-1? Or a really high lock_time, but it would not make it invalid,
> just delayed. Any suggestions here?
> >
> > >
> > > I agree that PoP seems complementary to BIP70.
> > >
> > >
> >
> > Thank you very much for your comments!
> >
> > /Kalle
>
>
> ------------------------------------------------------------------------------
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2023-06-07 15:32:41

- reply

📅 Original date posted:2015-04-27
📝 Original message:"Or a really high lock_time, but it would not make it invalid, just
delayed."
Ok, this was a bad idea, since nodes would have to keep it in memory.
Please disregard that idea...
Kalle
Den 27 apr 2015 14:35 skrev "Kalle Rosenbaum" <kalle at rosenbaum.se>:
>
> >
> > Some more use cases might be:
> > Waiting in comfort:
> > - Send a payment ahead of time, then wander over and collect the goods
> > after X confirmations.
> >
> > Authorized pickup :
> > - Hot wallet software used by related people could facilitate the use
> > of 1 of N multisig funds. Any one of the N wallets could collect goods
> > and services purchased by any of the others.
>
> I like this one, because it shows the power of reusing the transaction
data structure.
>
> >
> > Non-monetary gifts:
> > - Sender exports spent keys to a beneficiary, enabling PoP to work as a
> > gift claim
> >
> > Contingent services:
> > - Without Bob's permission, a 3rd party conditions action on a payment
> > made from Alice to Bob. For example, if you donated at least .02 BTC to
> > Dorian, you (or combining scenarios, any of your N authorized family
> > members), can come to my dinner party.
>
> This is an interesting one.
>
> >
> > I tried out your demo wallet and service and it worked as advertised.
> >
> > Could the same standard also be used to prove that a transaction COULD
> > BE created? To generalize the concept beyond actual payments, you could
> > call it something like proof of payment potential.
>
> I guess it's possible, but we'd have to remove the txid from the output,
since there is none. This is a way of saying "I'm in control of these
addresses". The other party/parties can then verify the funds on the
blockchain and watch those addresses for changes. Maybe there are some
interesting use cases here. Ideas?
>
> >
> > Why not make these proofs permanently INVALID transactions, to remove
> > any possibility of their being mined and spending everything to fees
> > when used in this way, and also in cases involving reorganizations?
>
> Yes. Initially I thought it would be enough that the funds are already
spent, but I think you're right here. Reorgs could be a problem. Worse, you
also might want to prove 0-confirmation transactions, in which case it's a
huge security problem. Someone might intercept the PoP and publish it on
the bitcoin network, spending all the funds. But I still would like wallets
to be able to build/verify PoPs with little or no modifications. Could we
possibly change the version number on the PoP to something other than 1?
Maybe 2^4-1? Or a really high lock_time, but it would not make it invalid,
just delayed. Any suggestions here?
>
> >
> > I agree that PoP seems complementary to BIP70.
> >
> >
>
> Thank you very much for your comments!
>
> /Kalle
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2023-06-07 15:32:41

- reply

📅 Original date posted:2015-04-27
📝 Original message:>
> Some more use cases might be:
> Waiting in comfort:
> - Send a payment ahead of time, then wander over and collect the goods
> after X confirmations.
>
> Authorized pickup :
> - Hot wallet software used by related people could facilitate the use
> of 1 of N multisig funds. Any one of the N wallets could collect goods
> and services purchased by any of the others.
I like this one, because it shows the power of reusing the transaction data
structure.
>
> Non-monetary gifts:
> - Sender exports spent keys to a beneficiary, enabling PoP to work as a
> gift claim
>
> Contingent services:
> - Without Bob's permission, a 3rd party conditions action on a payment
> made from Alice to Bob. For example, if you donated at least .02 BTC to
> Dorian, you (or combining scenarios, any of your N authorized family
> members), can come to my dinner party.
This is an interesting one.
>
> I tried out your demo wallet and service and it worked as advertised.
>
> Could the same standard also be used to prove that a transaction COULD
> BE created? To generalize the concept beyond actual payments, you could
> call it something like proof of payment potential.
I guess it's possible, but we'd have to remove the txid from the output,
since there is none. This is a way of saying "I'm in control of these
addresses". The other party/parties can then verify the funds on the
blockchain and watch those addresses for changes. Maybe there are some
interesting use cases here. Ideas?
>
> Why not make these proofs permanently INVALID transactions, to remove
> any possibility of their being mined and spending everything to fees
> when used in this way, and also in cases involving reorganizations?
Yes. Initially I thought it would be enough that the funds are already
spent, but I think you're right here. Reorgs could be a problem. Worse, you
also might want to prove 0-confirmation transactions, in which case it's a
huge security problem. Someone might intercept the PoP and publish it on
the bitcoin network, spending all the funds. But I still would like wallets
to be able to build/verify PoPs with little or no modifications. Could we
possibly change the version number on the PoP to something other than 1?
Maybe 2^4-1? Or a really high lock_time, but it would not make it invalid,
just delayed. Any suggestions here?
>
> I agree that PoP seems complementary to BIP70.
>
>
Thank you very much for your comments!
/Kalle
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2023-06-07 15:32:40

- reply

📅 Original date posted:2015-04-22
📝 Original message:Hi again
I've built a proof-of-concept for Proof of Payment. It's available at
http://www.rosenbaum.se:8080. The site contains links to the source code
for both the server and a Mycelium fork as well as pre-built apk:s.
I'm still very interested in feedback on this, so please let me know what
you think.
Stuff that has come up so far, and my answers:
* Some people think it's too complicated. I disagree. Using transactions as
the data structure actually makes it simple to implement both on the server
and in wallets. Just use existing wallet software to sign and verify PoPs.
* Other ideas on Proof of Payment use a single key from the proven
transaction, for example the first key from the first input of the
transaction. This is problematic when multisig and other P2SH transactions
are used. I also think that it's necessary to use *all* credentials used
for the transaction. Otherwise we wouldn't be sure that the sender actually
have all the needed credentials.
* Another suggestion is that a payment request from BIP70 is used as proof.
That is possible, but it's reusable which makes it inappropriate to send
over networks; If it is stolen somewhere, anyone can use it as many times
they like. As stated in BIP70, the payment request is suitable for dispute
resolution, more like a receipt. On the other hand, I think that PoP would
fit nicely into the workflow of BIP70: a) Read a url for the PoP request,
b) get the (possibly signed) PoP request. c) send the PoP through http POST
to the URL in the PoP request, d) profit!
* A thought of my own: The txid used in the PoP output is not strictly
necessary. It's more of a convenience for the verifier of the PoP. Without
it, the verifier would need to lookup the transaction based on the inputs
of the PoP,
Regards,
Kalle Rosenbaum
2015-03-14 19:16 GMT+01:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
> Den 14 mar 2015 00:59 skrev "Patrick Mccorry (PGR)" <
> patrick.mccorry at newcastle.ac.uk>:
> >
> > That all seems more complicated than it needs to be - the service you
> are paying knows that it had received a payment from some public key Q
> (regardless of script type, as all scripts require a public key).
>
> The service knows it had received a payment from Q1, Q2,...,Qn. A tx may
> have multiple inputs and each input may have several public keys.
>
> >
> > So I want to rent a movie, they send me a challenge and I respond with a
> zero knowledge proof to demonstrate that I am the owner of Q, and as they
> know that Q made a payment - then there is a proof of payment - as this is
> provided by the time stamped transaction on the blockchain - in this sense
> you are bootstrapping trust from the blockchain.
> >
>
> Ok. Without knowing much about zero knowledge proof, i guess you'd need a
> challenge/response for each of the keys Q1,..,Qn. If we settle on only a
> single key, what key from what input should we use? One input may be a
> multisig (2 of 3) input. Is it ok to settle on only one of the multisig
> keys? Probably not. I'd say that we need 2 of 3 signatures (just as in a
> bitcoin transaction), and not necessarily the same two that made the
> payment.
>
> > For all of your scenarios, a simple challenge-response scheme would
> work. Adding an op_return makes the payment transaction worse as it is now
> distinguishable on the blockchain - you want use information that is
> already available on that transaction.
>
> I'm not sure I follow. Do you mean that it's a problem that the PoP itself
> reveals what transaction I'm proving? Well, maybe it is a problem under
> some circumstances. The least you can do to protect yourself from revealing
> information to third party is to communicate over secure channels. Could
> you please elaborate on this?
>
> Anyway, if both the client and the server knows what transaction to prove
> (ad-sign example) you are right that the tx info is kind of redundant. But
> if we don't send the tx hints from server to client, the client user must
> manually select the transaction to prove which makes the user experience
> worse.
>
> Thank you very much for your comments,
>
> /Kalle
>
> >
> > Sent from my iPhone
> >
> > On 13 Mar 2015, at 19:58, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
> >
> >> Hi all,
> >>
> >> I've been thinking about how a person can prove that she has made a
> payment. I came up with an idea I call Proof of Payment (PoP) and I would
> highly appreciate your comments. Has something like this been discussed
> somewhere before?
> >>
> >> Use cases
> >>
> >> There are several scenarios in which it would be useful to prove that
> you have paid for something. For example:
> >> A pre-paid hotel room where your PoP functions as a key to the door.
> >> An online video rental service where you pay for a video and watch it
> on any device.
> >> An ad-sign where you pay in advance for e.g. 2-weeks exclusivity.
> During this period you can upload new content to the sign whenever you like
> using PoP.
> >> A lottery where all participants pay to the same address, and the
> winner of the T-shirt is selected among the transactions to that address.
> You exchange the T-shirt for a PoP for the winning transaction.
> >>
> >> These use cases can be achieved without any personal information (no
> accounts, no e-mails, etc) being involved.
> >>
> >> Desirable properties:
> >> A PoP should be generated on demand.
> >> It should only be usable once to avoid issues due to theft.
> >> It should be able to create a PoP for any payment, regardless of script
> type (P2SH, P2PKH, etc.).
> >> Current methods of proving a payment, as I know of:
> >> BIP0070, The PaymentRequest together with the transactions fulfilling
> the payment makes some sort of proof. However, it does not meet 1 or 2 and
> it obviously only meets 3 if the payment is made through BIP0070. Also,
> there's no standard way to request/provide the proof.
> >> Signing messages, chosen by the entity that the proof is provided to,
> with the private keys used to sign the transaction. This could meet 1 and 2
> but probably not 3. This is not standardized either.
> >> Proof of Payment, the data structure
> >>
> >> A proof of payment for a transaction T, PoP(T), is used to prove that
> one has ownership of the credentials needed to unlock all the inputs of T.
> It has the exact same structure as a bitcoin transaction with the same
> inputs as T and with a single OP_RETURN output:
> >>
> >> OP_RETURN PoP <txid> <nonce>
> >>
> >> | Field | Size [B] | Description |
> >> |-----------|----------|------------------------------------|
> >> | PoP | 3 | Literal identifying this as a PoP |
> >> | <txid> | 32 | The transaction to Prove |
> >> | <nonce> | 5 | Unsigned integer |
> >>
> >> The PoP is signed using the same signing process that is used for
> bitcoin transactions. The purpose of the nonce is to make it harder to use
> a stolen PoP. Once the PoP has reached the destination, that PoP is useless
> since the destination will generate a new nonce for every PoP.
> >>
> >> Proof of Payment, the process
> >> A proof of payment request is sent from the server to the wallet. The
> request contains:
> >> a random nonce
> >> a destination where to send the PoP, for example a https URL
> >> data hinting the wallet which transaction to create a proof for. For
> example:
> >> txid, if known by the server
> >> PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
> payment)
> >> amount
> >> label, message or other information from a BIP0021 URL
> >> The wallet identifies the transaction T, if possible. Otherwise asks
> the user to select among the ones that fit the hints in 1.3.
> >> The wallet checks that T is on the blockchain, meaning all the inputs
> are spent.
> >> The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
> sign it.
> >> The user confirms
> >> The UPoP(T) is signed by the wallet, creating PoP(T).
> >> The PoP is sent to the destination in 1.2.
> >> The server receiving the PoP validates it and responds with “valid” or
> “invalid”
> >> The wallet displays the response in some way to the user.
> >> Remarks:
> >> The method of transferring the PoP request at step 1 is not very well
> thought through, but I think we can extend BIP0021 to cater for this. For
> example read a URI, representing a PoP request, using QR code or NFC. A
> more advanced approach would be to extend BIP0070.
> >> The nonce must be randomly generated by the server for every new PoP
> request.
> >> Validating a PoP
> >>
> >> The server needs to validate the PoP and reply with “valid” or
> “invalid”. That process is outlined below:
> >> Check the format of the PoP. It must pass normal transaction checks,
> except for the inputs being already spent.
> >> Check the output script. It must conform to the OP_RETURN output format
> outlined above.
> >> Check that the nonce is the same as the one you requested.
> >> Check that the txid in the output is the transaction you actually want
> proof for. If you don’t know what transaction you want proof for, check
> that the transaction actually pays for the product/service you deliver (in
> the video rental case, find the transaction among all payments for that
> specific video).
> >> Check that the inputs of the PoP are exactly the same as in transaction
> T.
> >> Check the signatures of all the inputs, as would be done on a normal
> transaction.
> >> If the signatures are valid, the PoP is valid.
> >> Security issues
> >> Someone can intercept the PoP-request and change the destination so
> that the user sends the PoP to the bad actor.
> >> Someone can intercept the PoP-request and change for example the txid
> to trick the user to sign a PoP for another transaction than the intended.
> This can of course be avoided by actually looking at the UPoP before
> signing it. The bad actor could also set hints for a transaction that the
> user didn’t make, resulting in a broken service.
> >> Someone can steal a PoP and try to use the service hoping to get a
> matching nonce. Probability per try: 1/(2^40). The server should have
> mechanism for detecting a brute force attack of this kind, or at least slow
> down the process by delaying the PoP request by some 100 ms or so.
> >> Even if a wallet has no funds it might still be valuable as a generator
> for PoPs. This makes it important to keep the security of the wallet after
> it has been emptied.
> >> The first two issues are the same as for traditional bitcoin payments.
> They could be mitigated by using secure connections and possibly also
> extending BIP0070 to support PoPs.
> >>
> >> Further work
> >> Figure out how to make use of, and extend, BIP0070 for the purpose of
> PoPs
> >> Define an extension for BIP0021 to support PoP requests (something
> along the lines of BIP0072)
> >> Implement a proof-of-concept
> >> Possibly propose BIPs for the different parts.
> >> Looking forward to reading your comments
> >> Regards,
> >> Kalle Rosenbaum
> >>
> >>
> ------------------------------------------------------------------------------
> >> Dive into the World of Parallel Programming The Go Parallel Website,
> sponsored
> >> by Intel and developed in partnership with Slashdot Media, is your hub
> for all
> >> things parallel software development, from weekly thought leadership
> blogs to
> >> news, videos, case studies, tutorials and more. Take a look and join
> the
> >> conversation now. http://goparallel.sourceforge.net/
> >>
> >> _______________________________________________
> >> Bitcoin-development mailing list
> >> Bitcoin-development at lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>
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2023-06-07 15:31:53

- reply

📅 Original date posted:2015-03-14
📝 Original message:>
> Actually, the security of the PaymetRequest is pretty much out of your
>> control as soon as the PaymentRequest is created on the server. You have no
>> idea what the hotel does with it. Also if it's stored in the hotel server I
>> have to trust the hotel to keep it safe for me.
>>
>
> Well, yes. But if the hotel itself is hacked then the whole process is
> meaningless, no? The hacker could just make the hotel think the proof of
> payment is correct even though it was never made at all, for instance.
>
Maybe the hotel example is not perfect for this discussion. Let's instead
assume that the server holds yearly subscriptions to some expensive video
service. If that service stores PaymentRequests for all their subscribers,
and accept them as proof of payment, that would be similar to storing
username and (possibly hashed) passwords for all subscribers. If all the
PaymentRequests for all users are stolen, then they have to shut down all
accounts if they discover the theft. If they don't discover the theft the
"accounts" are out in the wild, for sale, for blackmail, etc.
Wouldn't it be better if the service don't accept the reusable
PaymentRequests as proof, and instead accept a proof generated on demand,
at the very moment it is needed, and that it is only usable once? From a
usability perspective there is no difference; The users simply need access
the service and authorize the proof being sent to the server.
>
>
>> Another thing is that you assume BIP0070 is used for payments, which
>> isn't necessarily is the case.
>>
>
> It's just a convenient place to put things. There are lots of useful
> features that need BIP 70. I hope eventually all wallets will support it.
>
I also hope BIP0070 will take off. It would greatly improve the user
experience. But even then, all payments are not BIP0070. BIP0070 is
primarily for merchants who have the skills, time and money to use
certificates. I don't think a lottery at the local church would want to set
up a secure BIP0070 server, but they still might want to use bitcoin for
their lottery.
Regards,
Kalle
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2023-06-07 15:31:53

- reply

📅 Original date posted:2015-03-14
📝 Original message:Den 14 mar 2015 00:59 skrev "Patrick Mccorry (PGR)" <
patrick.mccorry at newcastle.ac.uk>:
>
> That all seems more complicated than it needs to be - the service you are
paying knows that it had received a payment from some public key Q
(regardless of script type, as all scripts require a public key).
The service knows it had received a payment from Q1, Q2,...,Qn. A tx may
have multiple inputs and each input may have several public keys.
>
> So I want to rent a movie, they send me a challenge and I respond with a
zero knowledge proof to demonstrate that I am the owner of Q, and as they
know that Q made a payment - then there is a proof of payment - as this is
provided by the time stamped transaction on the blockchain - in this sense
you are bootstrapping trust from the blockchain.
>
Ok. Without knowing much about zero knowledge proof, i guess you'd need a
challenge/response for each of the keys Q1,..,Qn. If we settle on only a
single key, what key from what input should we use? One input may be a
multisig (2 of 3) input. Is it ok to settle on only one of the multisig
keys? Probably not. I'd say that we need 2 of 3 signatures (just as in a
bitcoin transaction), and not necessarily the same two that made the
payment.
> For all of your scenarios, a simple challenge-response scheme would work.
Adding an op_return makes the payment transaction worse as it is now
distinguishable on the blockchain - you want use information that is
already available on that transaction.
I'm not sure I follow. Do you mean that it's a problem that the PoP itself
reveals what transaction I'm proving? Well, maybe it is a problem under
some circumstances. The least you can do to protect yourself from revealing
information to third party is to communicate over secure channels. Could
you please elaborate on this?
Anyway, if both the client and the server knows what transaction to prove
(ad-sign example) you are right that the tx info is kind of redundant. But
if we don't send the tx hints from server to client, the client user must
manually select the transaction to prove which makes the user experience
worse.
Thank you very much for your comments,
/Kalle
>
> Sent from my iPhone
>
> On 13 Mar 2015, at 19:58, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>
>> Hi all,
>>
>> I've been thinking about how a person can prove that she has made a
payment. I came up with an idea I call Proof of Payment (PoP) and I would
highly appreciate your comments. Has something like this been discussed
somewhere before?
>>
>> Use cases
>>
>> There are several scenarios in which it would be useful to prove that
you have paid for something. For example:
>> A pre-paid hotel room where your PoP functions as a key to the door.
>> An online video rental service where you pay for a video and watch it on
any device.
>> An ad-sign where you pay in advance for e.g. 2-weeks exclusivity. During
this period you can upload new content to the sign whenever you like using
PoP.
>> A lottery where all participants pay to the same address, and the winner
of the T-shirt is selected among the transactions to that address. You
exchange the T-shirt for a PoP for the winning transaction.
>>
>> These use cases can be achieved without any personal information (no
accounts, no e-mails, etc) being involved.
>>
>> Desirable properties:
>> A PoP should be generated on demand.
>> It should only be usable once to avoid issues due to theft.
>> It should be able to create a PoP for any payment, regardless of script
type (P2SH, P2PKH, etc.).
>> Current methods of proving a payment, as I know of:
>> BIP0070, The PaymentRequest together with the transactions fulfilling
the payment makes some sort of proof. However, it does not meet 1 or 2 and
it obviously only meets 3 if the payment is made through BIP0070. Also,
there's no standard way to request/provide the proof.
>> Signing messages, chosen by the entity that the proof is provided to,
with the private keys used to sign the transaction. This could meet 1 and 2
but probably not 3. This is not standardized either.
>> Proof of Payment, the data structure
>>
>> A proof of payment for a transaction T, PoP(T), is used to prove that
one has ownership of the credentials needed to unlock all the inputs of T.
It has the exact same structure as a bitcoin transaction with the same
inputs as T and with a single OP_RETURN output:
>>
>> OP_RETURN PoP <txid> <nonce>
>>
>> | Field | Size [B] | Description |
>> |-----------|----------|------------------------------------|
>> | PoP | 3 | Literal identifying this as a PoP |
>> | <txid> | 32 | The transaction to Prove |
>> | <nonce> | 5 | Unsigned integer |
>>
>> The PoP is signed using the same signing process that is used for
bitcoin transactions. The purpose of the nonce is to make it harder to use
a stolen PoP. Once the PoP has reached the destination, that PoP is useless
since the destination will generate a new nonce for every PoP.
>>
>> Proof of Payment, the process
>> A proof of payment request is sent from the server to the wallet. The
request contains:
>> a random nonce
>> a destination where to send the PoP, for example a https URL
>> data hinting the wallet which transaction to create a proof for. For
example:
>> txid, if known by the server
>> PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
payment)
>> amount
>> label, message or other information from a BIP0021 URL
>> The wallet identifies the transaction T, if possible. Otherwise asks the
user to select among the ones that fit the hints in 1.3.
>> The wallet checks that T is on the blockchain, meaning all the inputs
are spent.
>> The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
sign it.
>> The user confirms
>> The UPoP(T) is signed by the wallet, creating PoP(T).
>> The PoP is sent to the destination in 1.2.
>> The server receiving the PoP validates it and responds with “valid” or
“invalid”
>> The wallet displays the response in some way to the user.
>> Remarks:
>> The method of transferring the PoP request at step 1 is not very well
thought through, but I think we can extend BIP0021 to cater for this. For
example read a URI, representing a PoP request, using QR code or NFC. A
more advanced approach would be to extend BIP0070.
>> The nonce must be randomly generated by the server for every new PoP
request.
>> Validating a PoP
>>
>> The server needs to validate the PoP and reply with “valid” or
“invalid”. That process is outlined below:
>> Check the format of the PoP. It must pass normal transaction checks,
except for the inputs being already spent.
>> Check the output script. It must conform to the OP_RETURN output format
outlined above.
>> Check that the nonce is the same as the one you requested.
>> Check that the txid in the output is the transaction you actually want
proof for. If you don’t know what transaction you want proof for, check
that the transaction actually pays for the product/service you deliver (in
the video rental case, find the transaction among all payments for that
specific video).
>> Check that the inputs of the PoP are exactly the same as in transaction
T.
>> Check the signatures of all the inputs, as would be done on a normal
transaction.
>> If the signatures are valid, the PoP is valid.
>> Security issues
>> Someone can intercept the PoP-request and change the destination so that
the user sends the PoP to the bad actor.
>> Someone can intercept the PoP-request and change for example the txid to
trick the user to sign a PoP for another transaction than the intended.
This can of course be avoided by actually looking at the UPoP before
signing it. The bad actor could also set hints for a transaction that the
user didn’t make, resulting in a broken service.
>> Someone can steal a PoP and try to use the service hoping to get a
matching nonce. Probability per try: 1/(2^40). The server should have
mechanism for detecting a brute force attack of this kind, or at least slow
down the process by delaying the PoP request by some 100 ms or so.
>> Even if a wallet has no funds it might still be valuable as a generator
for PoPs. This makes it important to keep the security of the wallet after
it has been emptied.
>> The first two issues are the same as for traditional bitcoin payments.
They could be mitigated by using secure connections and possibly also
extending BIP0070 to support PoPs.
>>
>> Further work
>> Figure out how to make use of, and extend, BIP0070 for the purpose of
PoPs
>> Define an extension for BIP0021 to support PoP requests (something along
the lines of BIP0072)
>> Implement a proof-of-concept
>> Possibly propose BIPs for the different parts.
>> Looking forward to reading your comments
>> Regards,
>> Kalle Rosenbaum
>>
>>
------------------------------------------------------------------------------
>> Dive into the World of Parallel Programming The Go Parallel Website,
sponsored
>> by Intel and developed in partnership with Slashdot Media, is your hub
for all
>> things parallel software development, from weekly thought leadership
blogs to
>> news, videos, case studies, tutorials and more. Take a look and join the
>> conversation now. http://goparallel.sourceforge.net/
>>
>> _______________________________________________
>> Bitcoin-development mailing list
>> Bitcoin-development at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
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2023-06-07 15:31:52

- reply

📅 Original date posted:2015-03-13
📝 Original message:Hi
No I don't agree with the analysis.
Yes, the PaymentRequest can be stored with the same security as the private
keys are stored. The big difference is that the keys never leave the
wallet. As soon as that PaymentRequest leaves the wallet on its way to the
hotel server, it is up for grabs which makes it inappropriate for use as a
proof of payment other than for resolving disputes and other one-time stuff.
/Kalle
2015-03-13 22:31 GMT+01:00 Mike Hearn <mike at plan99.net>:
> Hi Kalle,
>
> I think you're thinking along the right lines, but I am skeptical that
> this protocol adds much. A saved payment request is meant to be unique per
> transaction e.g. because the destination address is unique for that payment
> (for privacy reasons). Where would you store the signed payment request?
> Probably in the wallet. You could just extract the metadata that's useful
> for UI rendering into a separate structure and then encrypt the original
> full payment request under the wallet key. At least this is how I imagine
> it would work.
>
> So then, if someone can steal a payment request they can probably steal
> the wallet signing keys too, and thus signing a challenge with the wallet
> keys doesn't add much. It means the wallet doesn't have to store the
> PaymentRequest encrypted. But AFAICT that's about all it does.
>
> Do you agree with this analysis?
>
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2023-06-07 15:31:51

- reply

📅 Original date posted:2015-03-13
📝 Original message:Hi all,
I've been thinking about how a person can prove that she has made a
payment. I came up with an idea I call Proof of Payment (PoP) and I would
highly appreciate your comments. Has something like this been discussed
somewhere before?
*Use cases*
There are several scenarios in which it would be useful to prove that you
have paid for something. For example:
- A pre-paid hotel room where your PoP functions as a key to the door.
- An online video rental service where you pay for a video and watch it
on any device.
- An ad-sign where you pay in advance for e.g. 2-weeks exclusivity.
During this period you can upload new content to the sign whenever you like
using PoP.
- A lottery where all participants pay to the same address, and the
winner of the T-shirt is selected among the transactions to that address.
You exchange the T-shirt for a PoP for the winning transaction.
These use cases can be achieved without any personal information (no
accounts, no e-mails, etc) being involved.
Desirable properties:
1. A PoP should be generated on demand.
2. It should only be usable once to avoid issues due to theft.
3. It should be able to create a PoP for any payment, regardless of
script type (P2SH, P2PKH, etc.).
Current methods of proving a payment, as I know of:
- BIP0070, The PaymentRequest together with the transactions fulfilling
the payment makes some sort of proof. However, it does not meet 1 or 2 and
it obviously only meets 3 if the payment is made through BIP0070. Also,
there's no standard way to request/provide the proof.
- Signing messages, chosen by the entity that the proof is provided to,
with the private keys used to sign the transaction. This could meet 1 and 2
but probably not 3. This is not standardized either.
*Proof of Payment, the data structure*
A proof of payment for a transaction T, PoP(T), is used to prove that one
has ownership of the credentials needed to unlock all the inputs of T. It
has the exact same structure as a bitcoin transaction with the same inputs
as T and with a single OP_RETURN output:
OP_RETURN PoP <txid> <nonce>
| Field | Size [B] | Description |
|-----------|----------|------------------------------------|
| PoP | 3 | Literal identifying this as a PoP |
| <txid> | 32 | The transaction to Prove |
| <nonce> | 5 | Unsigned integer |
The PoP is signed using the same signing process that is used for bitcoin
transactions. The purpose of the nonce is to make it harder to use a stolen
PoP. Once the PoP has reached the destination, that PoP is useless since
the destination will generate a new nonce for every PoP.
*Proof of Payment, the process*
1. A proof of payment request is sent from the server to the wallet. The
request contains:
1. a random nonce
2. a destination where to send the PoP, for example a https URL
3. data hinting the wallet which transaction to create a proof for.
For example:
- txid, if known by the server
- PaymentRequest.PaymentDetails.merchant_data (in case of a
BIP0070 payment)
- amount
- label, message or other information from a BIP0021 URL
2. The wallet identifies the transaction T, if possible. Otherwise
asks the user to select among the ones that fit the hints in 1.3.
3. The wallet checks that T is on the blockchain, meaning all the inputs
are spent.
4. The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
sign it.
5. The user confirms
6. The UPoP(T) is signed by the wallet, creating PoP(T).
7. The PoP is sent to the destination in 1.2.
8. The server receiving the PoP validates it and responds with “valid”
or “invalid”
9. The wallet displays the response in some way to the user.
Remarks:
- The method of transferring the PoP request at step 1 is not very well
thought through, but I think we can extend BIP0021 to cater for this. For
example read a URI, representing a PoP request, using QR code or NFC. A
more advanced approach would be to extend BIP0070.
- The nonce must be randomly generated by the server for every new PoP
request.
*Validating a PoP*
The server needs to validate the PoP and reply with “valid” or “invalid”.
That process is outlined below:
1. Check the format of the PoP. It must pass normal transaction checks,
except for the inputs being already spent.
2. Check the output script. It must conform to the OP_RETURN output
format outlined above.
3. Check that the nonce is the same as the one you requested.
4. Check that the txid in the output is the transaction you actually
want proof for. If you don’t know what transaction you want proof for,
check that the transaction actually pays for the product/service you
deliver (in the video rental case, find the transaction among all payments
for that specific video).
5. Check that the inputs of the PoP are exactly the same as in
transaction T.
6. Check the signatures of all the inputs, as would be done on a normal
transaction.
7. If the signatures are valid, the PoP is valid.
*Security issues*
- Someone can intercept the PoP-request and change the destination so
that the user sends the PoP to the bad actor.
- Someone can intercept the PoP-request and change for example the txid
to trick the user to sign a PoP for another transaction than the intended.
This can of course be avoided by actually looking at the UPoP before
signing it. The bad actor could also set hints for a transaction that the
user didn’t make, resulting in a broken service.
- Someone can steal a PoP and try to use the service hoping to get a
matching nonce. Probability per try: 1/(2^40). The server should have
mechanism for detecting a brute force attack of this kind, or at least slow
down the process by delaying the PoP request by some 100 ms or so.
- Even if a wallet has no funds it might still be valuable as a
generator for PoPs. This makes it important to keep the security of the
wallet after it has been emptied.
The first two issues are the same as for traditional bitcoin payments. They
could be mitigated by using secure connections and possibly also extending
BIP0070 to support PoPs.
*Further work*
- Figure out how to make use of, and extend, BIP0070 for the purpose of
PoPs
- Define an extension for BIP0021 to support PoP requests (something
along the lines of BIP0072)
- Implement a proof-of-concept
- Possibly propose BIPs for the different parts.
Looking forward to reading your comments
Regards,
Kalle Rosenbaum
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