đ
Original date posted:2022-02-19
đ Original message:
On Fri, Feb 18, 2022 at 04:38:27PM -0800, Jeremy Rubin wrote:
> > As I said, it's a new kind of pinning attack, distinct from other types
> of pinning attack.
>
> I think pinning is "formally defined" as sequences of transactions which
> prevent or make it less likely for you to make any progress (in terms of
> units of computation proceeding).
Mentioning "computation" when talking about transactions is misleading:
blockchain transactions have nothing to do with computation.
> Something that only increases possibility to make progress cannot be
> pinning.
It is incorrect to say that all use-cases have the property that any version of
a transaction being mined is progress.
> If you want to call it something else, with a negative connotation, maybe
> call it "necromancing" (bringing back txns that would otherwise be
> feerate/fee irrational).
Necromancing might be a reasonable name for attacks that work by getting an
out-of-date version of a tx mined.
> In particular, for the use case you mentioned "Eg a third party could mess
> up OpenTimestamps calendars at relatively low cost by delaying the mining
> of timestamp txs.", this is incorrect. A third party can only accelerate
> the mining on the timestamp transactions, but they *can* accelerate the
> mining of any such timestamp transaction. If you have a single output chain
> that you're RBF'ing per block, then at most they can cause you to shift the
> calendar commits forward one block. But again, they cannot pin you. If you
> want to shift it back one block earlier, just offer a higher fee for the
> later RBF'd calendar. Thus the interference is limited by how much you wish
> to pay to guarantee your commitment is in this block as opposed to the next.
Your understanding of how OpenTimestamps calendars work appears to be
incorrect. There is no chain of unconfirmed transactions. Rather, OTS calendars
use RBF to _update_ the timestamp tx with a new merkle tip hash for to all
outstanding per-second commitments once per new block. In high fee situations
it's normal for there to be dozens of versions of that same tx, each with a
slightly higher feerate.
OTS calendars can handle any of those versions getting mined. But older
versions getting mined wastes money, as the remaining commitments still need to
get mined in a subsequent transaction. Those remaining commitments are also
delayed by the time it takes for the next tx to get mined.
There are many use-cases beyond OTS with this issue. For example, some entities
use "in-place" replacement for update low-time-preference settlement
transactions by adding new txouts and updating existing ones. Older versions of
those settlement transactions getting mined rather than the newer version
wastes money and delays settlement for the exact same reason it does in OTS.
If fee accounts or any similar mechanism get implemented, they absolutely
should be opt-in. Obviously, using a currently non-standard nVersion bit is a
possible approach. Conversely, with CPFP it may be desirable in the settlement
case to be able to *prevent* outputs from being spent in the same block. Again,
an nVersion bit is a possible approach.
> By the way, you can already do out-of-band transaction fees to a very
> similar effect, google "BTC transaction accelerator". If the attack were at
> all valuable to perform, it could happen today.
I just checked: all the BTC transaction accellerator services I could find look
to be either scams, or very expensive. We need compelling reasons to make this
nuisance attack significantly cheaper.
> Lastly, if you do get "necromanced" on an earlier RBF'd transaction by a
> third party for OTS, you should be relatively happy because it cost you
> less fees overall, since the undoing of your later RBF surely returned some
> satoshis to your wallet.
As I said above, no it doesn't.
--
https://petertodd.org 'peter'[:-1]@petertodd.org
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Peter Todd [ARCHIVE] /
npub1m2âŚa2np2
2023-06-09 13:05:09
in reply to nevent1qâŚfpj6
Author Public Key
npub1m230cem2yh3mtdzkg32qhj73uytgkyg5ylxsu083n3tpjnajxx4qqa2np2Published at
2023-06-09 13:05:09Event JSON
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Original date posted:2022-02-19\nđ Original message:\nOn Fri, Feb 18, 2022 at 04:38:27PM -0800, Jeremy Rubin wrote:\n\u003e \u003e As I said, it's a new kind of pinning attack, distinct from other types\n\u003e of pinning attack.\n\u003e \n\u003e I think pinning is \"formally defined\" as sequences of transactions which\n\u003e prevent or make it less likely for you to make any progress (in terms of\n\u003e units of computation proceeding).\n\nMentioning \"computation\" when talking about transactions is misleading:\nblockchain transactions have nothing to do with computation.\n\n\u003e Something that only increases possibility to make progress cannot be\n\u003e pinning.\n\nIt is incorrect to say that all use-cases have the property that any version of\na transaction being mined is progress.\n\n\u003e If you want to call it something else, with a negative connotation, maybe\n\u003e call it \"necromancing\" (bringing back txns that would otherwise be\n\u003e feerate/fee irrational).\n\nNecromancing might be a reasonable name for attacks that work by getting an\nout-of-date version of a tx mined.\n\n\u003e In particular, for the use case you mentioned \"Eg a third party could mess\n\u003e up OpenTimestamps calendars at relatively low cost by delaying the mining\n\u003e of timestamp txs.\", this is incorrect. A third party can only accelerate\n\u003e the mining on the timestamp transactions, but they *can* accelerate the\n\u003e mining of any such timestamp transaction. If you have a single output chain\n\u003e that you're RBF'ing per block, then at most they can cause you to shift the\n\u003e calendar commits forward one block. But again, they cannot pin you. If you\n\u003e want to shift it back one block earlier, just offer a higher fee for the\n\u003e later RBF'd calendar. Thus the interference is limited by how much you wish\n\u003e to pay to guarantee your commitment is in this block as opposed to the next.\n\nYour understanding of how OpenTimestamps calendars work appears to be\nincorrect. There is no chain of unconfirmed transactions. Rather, OTS calendars\nuse RBF to _update_ the timestamp tx with a new merkle tip hash for to all\noutstanding per-second commitments once per new block. In high fee situations\nit's normal for there to be dozens of versions of that same tx, each with a\nslightly higher feerate.\n\nOTS calendars can handle any of those versions getting mined. But older\nversions getting mined wastes money, as the remaining commitments still need to\nget mined in a subsequent transaction. Those remaining commitments are also\ndelayed by the time it takes for the next tx to get mined.\n\nThere are many use-cases beyond OTS with this issue. For example, some entities\nuse \"in-place\" replacement for update low-time-preference settlement\ntransactions by adding new txouts and updating existing ones. Older versions of\nthose settlement transactions getting mined rather than the newer version\nwastes money and delays settlement for the exact same reason it does in OTS.\n\nIf fee accounts or any similar mechanism get implemented, they absolutely\nshould be opt-in. Obviously, using a currently non-standard nVersion bit is a\npossible approach. Conversely, with CPFP it may be desirable in the settlement\ncase to be able to *prevent* outputs from being spent in the same block. Again,\nan nVersion bit is a possible approach.\n\n\u003e By the way, you can already do out-of-band transaction fees to a very\n\u003e similar effect, google \"BTC transaction accelerator\". If the attack were at\n\u003e all valuable to perform, it could happen today.\n\nI just checked: all the BTC transaction accellerator services I could find look\nto be either scams, or very expensive. We need compelling reasons to make this\nnuisance attack significantly cheaper.\n\n\u003e Lastly, if you do get \"necromanced\" on an earlier RBF'd transaction by a\n\u003e third party for OTS, you should be relatively happy because it cost you\n\u003e less fees overall, since the undoing of your later RBF surely returned some\n\u003e satoshis to your wallet.\n\nAs I said above, no it doesn't.\n\n-- \nhttps://petertodd.org 'peter'[:-1]@petertodd.org\n-------------- next part --------------\nA non-text attachment was scrubbed...\nName: signature.asc\nType: application/pgp-signature\nSize: 833 bytes\nDesc: not available\nURL: \u003chttp://lists.linuxfoundation.org/pipermail/lightning-dev/attachments/20220219/e3194806/attachment-0001.sig\u003e",
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