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LibraryMarkets2017Design paperCorpus record

Partially Signed Bitcoin Transactions

BIP 174. Andrew Chow.

A PSBT is a standard container for a transaction, the inputs' previous outputs, and the partial signatures. Roles are creator, updater, signer, combiner, finaliser and extractor.

A reading of the public document. Not a copy of it, and not a claim about a later network that reused the name.

A custody workflow that cannot show the PSBT's outputs to the signer has hidden the only thing the signer is for.
Evidence
Primary paper
Re-measured
No
Assumptions
3
Records linked
4

Code

Source, repository, and what is actually hosted

  • BIP 174https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki
  • bitcoin/bipsRepository taken from the source URL. 97 other studies in this library cite the same repository. This is not an audit.
  • Full upstream textMirrored 2026-10-10 under BSD-2-Clause. The desk study is not part of that licence.
  • Add to a reading list

01 Claim ledger

What the paper is allowed to say

Each row is a sentence already in the study. The status is the same on every row: a model claim, not a live measurement.

  1. Claim 01 · Paper model

    The defect

    A multi-signature transaction used to be a private file format for each wallet. Hardware wallets, coordinators and humans could not pass one object around.

  2. Claim 02 · Paper model

    The rule

    A PSBT is a standard container for a transaction, the inputs' previous outputs, and the partial signatures. Roles are creator, updater, signer, combiner, finaliser and extractor.

  3. Claim 03 · Paper model

    How it is put together

    The unsigned transaction and the signatures travel together. A signer does not have to trust a coordinator with keys. The format is versioned. v2 is a later BIP.

  4. Claim 04 · Paper model

    Where the claim stops

    PSBT does not choose the policy. A 2-of-3 is still a wallet decision.

02 Three cuts

Observation, model, falsifier

A desk does not stop at the summary. Each claim is cut three ways, using only this study's own assumptions and checks. Nothing here is a new figure.

  1. 01 The defect

    Observation

    What the study says

    A multi-signature transaction used to be a private file format for each wallet. Hardware wallets, coordinators and humans could not pass one object around.

    Model

    What has to hold

    PSBT does not choose the policy. A 2-of-3 is still a wallet decision.

    Falsifier

    What would retire it

    Which role is this software playing?

  2. 02 The rule

    Observation

    What the study says

    A PSBT is a standard container for a transaction, the inputs' previous outputs, and the partial signatures. Roles are creator, updater, signer, combiner, finaliser and extractor.

    Model

    What has to hold

    A malicious creator can still propose a payment the signer must read.

    Falsifier

    What would retire it

    Can the signer see every output?

  3. 03 How it is put together

    Observation

    What the study says

    The unsigned transaction and the signatures travel together. A signer does not have to trust a coordinator with keys. The format is versioned. v2 is a later BIP.

    Model

    What has to hold

    A malicious creator can still propose a payment the signer must read.

    Falsifier

    What would retire it

    Can the signer see every output?

  4. 04 Where the claim stops

    Observation

    What the study says

    PSBT does not choose the policy. A 2-of-3 is still a wallet decision.

    Model

    What has to hold

    PSBT does not choose the policy. A 2-of-3 is still a wallet decision.

    Falsifier

    What would retire it

    Which role is this software playing?

03 Sequence

One action, as an operating tape

  1. 01Create a PSBT with inputs and outputs.
  2. 02Each signer adds a partial signature.
  3. 03A finaliser attaches the witness and an extractor broadcasts.
  4. 04Which role is this software playing?

04 Load-bearing

The argument, and where a pitch drops it

  1. Why it is still on the desk

    The cut

    A custody workflow that cannot show the PSBT's outputs to the signer has hidden the only thing the signer is for.

    Why it carries weight

    If this cut is skipped, the paper's name is being used without the mechanism that makes the name mean anything.

    Where it is dropped

    A malicious creator can still propose a payment the signer must read.

  2. After the text

    The cut

    Hardware wallets standardised on this. BIP 370 updates the format. The roles are the 2017 idea.

    Why it carries weight

    If this cut is skipped, the paper's name is being used without the mechanism that makes the name mean anything.

    Where it is dropped

    The format is not a custody model.

05 Register

What has to be true

  • Model · Not re-measured

    PSBT does not choose the policy. A 2-of-3 is still a wallet decision.

  • Model · Not re-measured

    A malicious creator can still propose a payment the signer must read.

  • Model · Not re-measured

    The format is not a custody model.

06 Divergence

What happened after the paper

Hardware wallets standardised on this. BIP 370 updates the format. The roles are the 2017 idea.

A later client, parameter set, or reward formula is a different object. Cite this paper for the mechanism. Cite a primary release for the network. This desk has not re-run the proof.

07 Pre-mortem

What to check before you use the idea

  4. 0 of 3 marked on this browser. A mark is a reading note, not a pass, a rating, or a recommendation.

08 Anatomy

The paper, in the order a builder needs

The problem it names

A multi-signature transaction used to be a private file format for each wallet. Hardware wallets, coordinators and humans could not pass one object around.

What the design proposes

  • The unsigned transaction and the signatures travel together.
  • A signer does not have to trust a coordinator with keys.
  • The format is versioned. v2 is a later BIP.

How the mechanism is specified

  • Create a PSBT with inputs and outputs.
  • Each signer adds a partial signature.
  • A finaliser attaches the witness and an extractor broadcasts.

What this page does not treat as proven

  • PSBT does not choose the policy. A 2-of-3 is still a wallet decision.
  • A malicious creator can still propose a payment the signer must read.
  • The format is not a custody model.

Why the desk still reads it

A custody workflow that cannot show the PSBT's outputs to the signer has hidden the only thing the signer is for.

09 Lexicon

Terms, opened into the record

Updater
A party that adds input metadata the signer needs.
Finaliser
The party that turns partial signatures into a valid witness.

10 Repository

Every linked record on this page

Underlined words open a page that already exists: a concept, a protocol profile, a failure record, or another paper. If a word is not underlined, this desk does not have a record for it.

Upstream

The file, in full

Licence recorded on the mirror: BSD-2-Clause. Canonical file: https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki. Numbers and web addresses in the file open a study or the address itself.

Loading the mirrored file.

This is Blockchain Lab's reading of a public design paper. It is not the paper, not a copy of it, and not an offer of tokens, equity, custody or a partnership. Later network behaviour can diverge from the text. Nothing here is investment, legal or technical advice.

Research status: Design paper. Last reviewed: 1 October 2026. This is a reading of a public paper, not investment, legal or security advice.