Antoine Riard [ARCHIVE] on Nostr: 📅 Original date posted:2020-01-29 📝 Original message: Hey thanks for this ...

📅 Original date posted:2020-01-29
📝 Original message:
Hey thanks for this proposal!

2 high-level questions:

What about multi-party tx construction ? By multi-party, let's define
Alice initiate a tx construction to Bob and then Bob announce a
construction to Caroll and "bridge" all inputs/outputs
additions/substractions
in both directions. I think the current proposal hold, if you are a bit more
tolerant and bridge peer don't send a tx_complete before receiving ones
from all its peers.

What about transactions format ? I think we should coordinate with Coinjoin
people to converge to a common one to avoid leaking protocol usage when
we can hinder under Taproot. Like setting the nLocktime or sorting inputs
in some protocol-specific fashion. Ideally we should have a BIP for format
but every layer 2 protocols its own set of messages concerning the
construction.

> nLocktime is always set to 0x000000
Maybe we can implement anti-fee sniping and mask among wallet core
txn set:
https://github.com/bitcoin/bitcoin/blob/aabec94541e23a67a9f30dc2c80dab3383a01737/src/wallet/wallet.cpp#L2519
?

> In the case of a close, a failed collaborative close would result in an
error and a uninlateral close"
Or can we do first a mutual closing tx, hold tx broadcast for a bit if
"opt_dual_fund"
is signaled to see if a tx_construction + add_funding_input for the channel
is received
soon ? At least that would be a dual opt-in to know than one party can
submit a funding-outpoint
as part of a composed tx ?

Antoine

Le lun. 27 janv. 2020 à 20:51, lisa neigut <niftynei at gmail.com> a écrit :

> Some of the feedback I received from the check-in for the dual-funding
> proposal this past Monday was along the lines that we look at simplifying
> for breaking it into smaller, more manageable chunks.
>
> The biggest piece of the dual-funding protocol update is definitely the
> move from a single peer constructing a transaction to two participants.
> We're also going to likely want to reuse this portion of the protocol for
> batched closings and splicing. To that extent, it seemed useful to
> highlight it in a separate email.
>
> This is a change from the existing proposal in the dual-funding PR #524
> <https://github.com/lightningnetwork/lightning-rfc/pull/524>; -- it allows
> for the removal of inputs and outputs.
>
> The set of messages are as follows.
>
>
> Note that the 'initiation' of this protocol will be different depending
> on the case of the transaction (open, close or splice):
>
> 1. type: 440 `tx_add_input`
>
> 2. data:
>
> * [`32*byte`:`channel_identifier`]
>
> * [`u64`:`sats`]
>
> * [`sha256`:`prevtx_txid`]
>
> * [`u32`:`prevtx_vout`]
>
> * [`u16`:`prevtx_scriptpubkey_len`]
>
> * [`prevtx_scriptpubkey_len*byte`:`prevtx_scriptpubkey`]
>
> * [`u16`:`max_witness_len`]
>
> * [`u16`:`scriptlen`]
>
> * [`scriptlen*byte`:`script`]
>
> * [`byte`:`signal_rbf`]
>
> 1. type: 442 `tx_add_output`
>
> 2. data:
>
> * [`32*byte`:`channel_identifier`]
>
> * [`u64`:`sats`]
>
> * [`u16`:`scriptlen`]
>
> * [`scriptlen*byte`:`script`]
>
> 1. type: 444 `tx_remove_input`
>
> 2. data:
>
> * [`32*byte`:`channel_identifier`]
>
> * [`sha256`:`prevtx_txid`]
>
> * [`u32`:`prevtx_vout`]
>
> 1. type: 446 `tx_remove_output`
>
> 2. data:
>
> * [`32*byte`:`channel_identifier`]
>
> * [`u64`:`sats`]
>
> * [`u16`:`scriptlen`]
>
> * [`scriptlen*byte`:`script`]
>
> 1. type: 448 `tx_complete`
>
> 2. data:
>
> * [`32*byte`:`channel_identifier`]
>
> * [`u16`:`num_inputs`]
>
> * [`u16`:`num_outputs`]
>
> 1. type: 448 `tx_sigs`
>
> 2. data:
>
> * [`channel_id`:`channel_identifier`]
>
> * [`u16`:`num_witnesses`]
>
> * [`num_witnesses*witness_stack`:`witness_stack`]
>
> 1. subtype: `witness_stack`
>
> 2. data:
>
> * [`sha256`:`prevtx_txid`]
>
> * [`u32`:`prevtx_vout`]
>
> * [`u16`:`num_input_witness`]
>
> * [`num_input_witness*witness_element`:`witness_element`]
>
> 1. subtype: `witness_element`
>
> 2. data:
>
> * [`u16`:`len`]
>
> * [`len*byte`:`witness`]
>
>
>
> ## General Notes
>
> - Validity of inputs/outputs is not checked until both peers have sent
> consecutive `tx_complete` messages.
>
> - Duplicate inputs or outputs is a protocol error.
>
> - Feerate is set by the initiator, or in the case of a closing
> transaction, negotiated before the transaction construction is initiated.
>
> - Every peer pays fees for the inputs + outputs they contribute, plus
> enough to cover the maximum estimate of their witnesses. Overpayment of
> fees is permissible.
>
> - Initiator is responsible for contributing the output/input in question,
> i.e. the
>
> funding output in the case of an opening, or the funding input in the
> case of a close.
>
> (This means that the opener will pay for the opening output). In the
> case of a splice,
>
> the initiator of the splice pays for the funding tx's inclusion as an
> input and the
>
> new 'funding tx' output.
>
> - Any contributor may signal that their input is RBF'able. The nSequence
> for this input should be set to 0xFEFF FFFF, 0xFFFFFFFF otherwise.
>
> - The initiating peer is understood to be paying the fee for the shared
> transaction fields (nVersion [4], segwit marker + flag [2], input + output
> counts [2-18], witness count [1-9], nLocktime [4]; total [13-40bytes])
>
> - Inputs MUST be segwit compatible (PW* or P2SH-PW*)
>
> - All output scripts must be standard
>
> - nLocktime is always set to 0x00000000.
>
> - The `num_inputs` and `num_outputs` in `tx_complete` is a count of that
> peer’s final input and output contributions, net any removals.
>
> - Either peer may add or remove inputs and outputs until both peers have
> successfully
>
> exchanged a `tx_complete` message in succession.
>
> - Either peer may only add or remove their own input or output.
>
> - In the case that a `tx_complete` agreement cannot be reached, either
> peer may
>
> fail the channel or open protocol (whatever is reasonable for the
> particular case)
>
> - In the case of a splice, this would be a soft error (channel returns
> to normal operation until
>
> otherwise failed or closed.)
>
> - In the case of an open, this would be a failure to open the channel.
>
> - In the case of a close, a failed collaborative close would result in
> an error and a unilateral close.
>
> ### Considering the Simple Open case (2 parties)
>
> - Both peers signal `opt_dual_fund`
>
> - Opener initiates a channel open with `open_channel2` message, indicating
> the feerate for the opening transaction
>
> - Accepter signals acceptance of channel open as proposed, including
> proposed feerate, via `accept_channel2`
>
> - Opener sends `tx_add_output`, with the funding output for the sum of
> both peer’s funding_amount
>
> - Opener sends `tx_add_input` for each input the wish to add to the
> funding transaction
>
> - Opener sends `tx_add_output` for their change
>
> - Opener sends `tx_complete`
>
> - Accepter sends `tx_add_input` for each input they wish to add to the
> funding transaction
>
> - Accepter sends `tx_add_output` for their change.
>
> - Accepter sends `tx_complete`
>
> - Opener sends `tx_complete`
>
> - Opener and accepter exchange commitment signatures; etc.
>
> ### Considering the Splice case:
>
> - Both peers signal `opt_splice_ok`
>
> - One peer initiates a splice, also signaling the feerate for the
> transaction. Exact protocol unspecified herein.
>
> - Initiator sends `tx_add_input` with the original funding output
>
> - Initiator sends `tx_add_output` with the new, post-splice funding output
>
> - Initiator sends `tx_add_input/output` as needed to add all desired
> inputs + outputs
>
> - Initiator sends `tx_complete`
>
> - Peer sends `tx_add_input/output` as needed to add all desired inputs +
> outputs
>
> - Initiator sends `tx_complete`
>
> - Peer sends `tx_complete`
>
> - Initiator + peer exchange commitment signatures, etc.
>
> ### Considering the Close case:
>
> - Both peers signal `opt_collaborative_close` in their `node_announcement`.
>
> - A peer initiates a close sending a `shutdown`, as per usual.
>
> - A feerate is negotiated. Out of band for this particular portion of the
> protocol.
>
> -The closing initiator (peer which first sent `shutdown`), sends
> `tx_add_input` to spend the funding output and `tx_add_output` to add their
> output for the channel closure.
>
> - The peer responds with `tx_add_output`, adding their output to the close
> transaction.
>
> - If `option_upfront_shutdown_script` is flagged but no such output with a
> value at or within a reasonable feerate gap of the peer's funding output is
> present, then the peer must fail the channel.
>
>
> ## Updating a collaborative transaction with RBF:
>
> - If any input is flagged as RBF’able, then the transaction is considered
> eligible for RBF
>
> - RBF can be initiated by either party, and serves as an initiation for
> another round of transaction composition, as outlined above.
>
> - Note that this section has been cribbed and re-purposed from the
> original RBF proposal for splicing, see
> https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-November/001621.html
>
> 1. type: 45 (`init_rbf`) (`option_collaborative_rbf`)
>
> 2. data:
>
> * [`32`:`channel_id`]
>
> * [`4`:`fee_step`]
>
> Each `fee_step` adds 1/4 (rounded down) to the initial
>
> transaction feerate. eg. if the initial feerate was 512 satoshis per
> kiloweight, `fee_step` 1
>
> is 512 + 512 / 4 = 640, `fee_step` 2 is 640 + 640 / 4 = 800.
>
> The sender:
>
> - MUST set `fee_step` greater than zero and greater than any prior
> `fee_step`.
>
> The recipient:
>
> - if the new fee exceeds the sender's current balance minus reserve
>
> after it is applied to the splice transaction:
>
> - MUST error.
>
>
>
> NOTES:
>
> 1. 1/4 is a reasonable minimal RBF, but as each one requires more
>
> tracking by the recipient, serves to limit the number you can create.
>
> 2. Rule 4 of BIP125 requires a feerate increase to at least surpass the
> minimum transaction relay setting. Ratcheting by 25% should satisfy this
> requirement
>
> 3. An additional rule will be added to the checks of an RBF transaction
> that it must include at least one identical, replaceable input as the
> original transaction.
>
> _______________________________________________
> Lightning-dev mailing list
> Lightning-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev
>
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