BIP-0322: clarify motivation/purpose, add prefix, clarify Proof of Funds format, describe PSBT based signing by guggero · Pull Request #2141 · bitcoin/bips

guggero · 2026-04-14T14:32:54Z

This PR is an attempt to push this PR forward, hopefully closer to a Complete state.

If it helps the process and @kallewoof agrees, I'm volunteering to be named as a deputy for this BIP.

The PR addresses the following discussion items:

BIP-322 basic support bitcoin#24058 (comment)
- Distinction between "signer receives fund with the address" and "signer sent a prior transaction": addressed, only first is supported by the BIP
https://bitcoin.stackexchange.com/questions/126277/where-can-i-use-bip322-to-sign-a-message-to-verify-a-multisig-address
- Inability to prove private key possession, differentiation between address signature and UTXO set completion: Use case and motivation is clarified accordingly
https://groups.google.com/g/bitcoindev/c/RCi1Exs0ZvQ/m/vp6Xo36aBwAJ
- Collecting an authentic UTXO set for a given list of addresses: clarified that this is out of scope of the BIP.
- Prefix for signing result: added a proposal for a prefix.
BIP-322: Generic signed message format bitcoin#16440 (comment)
- Usefulness and completeness of Proof of Funds: This PR suggests a way that at least allows offline verification of the Proof of Funds variant by providing the UTXO information using a finalized PSBT. It remains to be discussed if we should instead completely remove the Proof of Funds use case in this BIP (which was suggested several times but I don't have an opinion about it)

TODO (will follow up with these items soon):

BIP-322: Generic signed message format bitcoin#16440 (comment)
- Clean up wording: Clarify that there might not always be a cryptographic signature involved (e.g. pure script spend address types)
Update btcd pull request to reflect above changes, update test vectors in this PR (prefix and Proof of Funds implementation)
Rebase and update after BIP174: Deduplicate type definitions by introducing registry file #2135 is merged

@murchandamus I went through the different discussions you linked and also both Bitcoin Core PRs and tried to extract all discussion items that I felt were not yet addressed.
If anyone feels like a previous discussion item is missing here and not yet addressed by my changes, please comment below!

jonatack · 2026-04-14T15:28:01Z

Thank you @guggero for picking this up.

If it helps the process and @kallewoof agrees, I'm volunteering to be named as a deputy for this BIP.

@kallewoof thoughts? (If helpful, see BIP3 here for details about the Deputy role.)

murchandamus

Partial review of the first three commits.

kallewoof · 2026-04-14T23:25:59Z

Thank you @guggero for picking this up.

If it helps the process and @kallewoof agrees, I'm volunteering to be named as a deputy for this BIP.

@kallewoof thoughts? (If helpful, see BIP3 here for details about the Deputy role.)

Sounds good to me!

guggero · 2026-04-15T05:17:56Z

I updated the prefixes to be fixed-size (smp, ful, pof) and removed the colon to make copy/paste errors by users less likely.

@murchandamus I don't really understand the failing CI check... Am I supposed to change the background color of the row in the README?

guggero · 2026-04-15T12:48:40Z

I've implemented the proposed changes (prefix, Proof of Funds format) in the btcd PR and updated the test vectors here. With that, all (current) TODOs are addressed and I think this PR is ready for a closer look by anyone interested.

murchandamus

Finished my first pass. I think it’s great that you want to pick up this proposal and bring it up to speed. Strong concept ACK. You also seem to have buy-in from @kallewoof, which is great.
Given the age of the proposal and the breaking change, I would heartily recommend that you write to the mailing list about the changes you are proposing in this PR.

murchandamus

Oh one more observation:

This re-formats the document for easier editing and diff viewing. Wiki syntax is weird for lists and line wraps break them. Simple lists were changed to <ul> or <ol> tags but complex lists remain as they are to not bloat the diff too much.

This fixes small inconsistencies or incomplete definitions based on previous, already merged changes.

This addresses two discussion items: - The list of UTXOs should not be interpreted as a "proof that no other UTXOs for an address exist". - The BIP only addresses "signer receives funds with the address" and not "signer sent a previous transaction" use case.

Since the term "signature" can be pretty overloaded dependin on the context, we clarify what it actually means in this BIP.

This commit proposes a fix for the problem that an offline verifier previously was not able to even verify the witness stack of additional inputs. By providing the full finalized PSBT, a verifier has all the input data necessary to run the script through the validation engine. We require the PSBT to be finalized to make sure it contains the final script witness or final script sig but no extra potentially privacy-sensitive fields. The Non-Witness and Witness UTXO fields are explicitly allowed for finalized PSBTs, which makes the format perfect for the use case.

This commit proposes a new PSBT input field type for transporting the message to be signed to different signers in a multisig signing use case.

This commit updates the test vectors to reflect all the changes in the previous commits and also introduces new test vectors for the Proof of Funds variant.

As described in BIP-0003, the comments section is no longer required. Instead we add all relevant discussions.

guggero · 2026-04-20T07:52:59Z

Thank you all for your inputs and reviews so far! As you might already have received in your respective inboxes, my message to the mailing list has been published: https://groups.google.com/g/bitcoindev/c/qd6BNz9gxCk

jonatack

Given the work here, would it make sense for @guggero to be an author? @kallewoof

murchandamus

I gave the document another full read, it looks good to me. I left one more suggestion.

murchandamus

I went over the commits one more time, LGTM. It might be good to have a PSBT expert take a look. Are you otherwise still waiting for review or is this ready to go from your perspective?

Edit: Ava Chow took a look and stated "seems fine" above in #2141 (comment).

guggero · 2026-04-22T06:36:23Z

Are you otherwise still waiting for review or is this ready to go from your perspective?

I didn't consult with @kallewoof about my suggested changes before opening the PR, as I wanted to show a complete picture before starting any discussions.
So a quick word from the original author would be appreciated to ensure my updates still align with the initial vision for the BIP.

And I also want to give the mailing list thread a bit of time for discussions to unfold. There already is a proposal for a change to move the PSBT field from an input field to a global field.

Detailed review is definitely welcome but a merge would be a bit premature at this point IMO.

murchandamus · 2026-04-22T22:51:14Z

Okay great, let’s revisit in a week or so, on April 28th or later.

jonatack added Proposed BIP modification PR by non-owner to update BIP content Pending acceptance This BIP modification requires sign-off by the champion of the BIP being modified labels Apr 14, 2026

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guggero force-pushed the bip-0322-finalization branch 2 times, most recently from f3ffd34 to 7809e72 Compare April 15, 2026 04:47

guggero force-pushed the bip-0322-finalization branch from d9d4bf3 to 1ee1a21 Compare April 15, 2026 12:54

bucko13 mentioned this pull request Apr 15, 2026

April 2026 austinbitdevs/austinbitdevs.com#65

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brenorb mentioned this pull request Apr 17, 2026

Abril 2026 ClubeBitcoinUnB/bitdevs.bsb.br#41

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guggero added 11 commits April 20, 2026 09:43

BIP-0322: wrap long lines at 100 characters

6f3fce2

This re-formats the document for easier editing and diff viewing. Wiki syntax is weird for lists and line wraps break them. Simple lists were changed to <ul> or <ol> tags but complex lists remain as they are to not bloat the diff too much.

BIP-0322: small semantic and formatting fixes

bbaf40c

This fixes small inconsistencies or incomplete definitions based on previous, already merged changes.

BIP-0322: reference btcd implementation

665d960

BIP-0322: clarify terminology used

8a46a5b

Since the term "signature" can be pretty overloaded dependin on the context, we clarify what it actually means in this BIP.

BIP-0322: add prefix to message signature

c2850a0

BIP-0174+BIP-0322: describe PSBT based signing

9fae276

This commit proposes a new PSBT input field type for transporting the message to be signed to different signers in a multisig signing use case.

BIP-0322: update test vectors

77fe1fc

This commit updates the test vectors to reflect all the changes in the previous commits and also introduces new test vectors for the Proof of Funds variant.

BIP-0322: add guggero as deputy

46fe60e

BIP-0322: remove comments, add discussion links

ff4c657

As described in BIP-0003, the comments section is no longer required. Instead we add all relevant discussions.

guggero force-pushed the bip-0322-finalization branch from 81b5a1c to 78c96cf Compare April 20, 2026 07:45

README+BIP-0322: add changelog, mark Complete

3300b28

guggero force-pushed the bip-0322-finalization branch from 78c96cf to 3300b28 Compare April 20, 2026 07:51

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fixup! BIP-0322: remove comments, add discussion links

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BIP Draft: Quantum-Resistant Transition for Dormant P2PKH Addresses #2147

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