# Bitcoin message signatures: proof of control with clear limits A Bitcoin message signature lets a verifier check a response tied to a stated message and spending condition under a supported format. It is evidence with limits, not automatic proof of personal identity, legal ownership or permanent control of funds. BIP-322 broadens message verification beyond legacy address types, while explicitly warning that someone can sign on another person’s behalf and that circumstances can change immediately afterward. Evidence: [Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki) Canonical: https://degreesofsatoshi.com/encyclopedia/bitcoin-message-signatures/ Published: 2026-10-02 Substantively modified: 2026-10-02 Independently verified by an automated reviewer: 2026-10-02T19:29:20.637Z Data current through: 2026-10-02 AI-assisted research and drafting with a separate automated source-verification pass; no external expert or named human review is implied. ## Key facts - **Message matters:** The exact agreed text is part of verification ([Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki)) - **Format matters:** Legacy, simple and full formats differ ([Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki)) - **Limits:** No permanent or exclusive control guarantee ([Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki)) ## Specify what the signature is meant to establish A verifier should supply a fresh, purpose-specific challenge and preserve the exact signed text, destination and signature format. Otherwise an old proof may be reused outside the context in which the signer intended it. The result should be reported as verification of that challenge. An illustrative message might identify a particular invoice review and its date. It should not make the verifier infer unrelated facts such as the signer’s name, the origin of funds or ownership of every address in a wallet. Evidence: [Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki) ## Use a format the wallet and verifier both understand The cited BIP restricts the legacy format to legacy P2PKH addresses. BIP-322 defines broader script-based formats, including simple and full variants, and allows an inconclusive result when a verifier does not understand required conditions. A failed verification can therefore be a format or implementation mismatch rather than proof of dishonesty. BIP-322’s virtual-transaction construction includes an invalid real-network input so that its message proof is not a spendable ordinary payment. Do not substitute an arbitrary transaction-signing request for the documented message-signing workflow. Evidence: [Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki) ## Keep the conclusion narrower than ownership A key holder may sign messages for someone else without agreeing to move funds for that person. A key may be shared, compromised or changed after the proof. The specification explicitly states that no message-signing protocol can eliminate these limits. It also does not prove that the signer created a particular historical payment. Combine signatures with the appropriate independent records when investigating identity or a commercial claim. Evidence: [Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki) ## Questions ### Does signing a message send bitcoin? A correctly implemented documented message-signing format is distinct from authorizing an ordinary payment. BIP-322 uses virtual transactions that cannot themselves be spent on a real network. Still inspect which operation the wallet actually requests. Evidence: [Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki) ### Does a signed message prove someone owns all coins at an address? No. Verification is evidence about a particular response and script condition. It does not establish exclusive or lasting control, legal ownership, liabilities or the willingness to authorize a real spend. Evidence: [Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki) ## Claims and scope ### bitcoin-message-signatures-quick-answer A Bitcoin message signature lets a verifier check a response tied to a stated message and spending condition under a supported format. It is evidence with limits, not automatic proof of personal identity, legal ownership or permanent control of funds. BIP-322 broadens message verification beyond legacy address types, while explicitly warning that someone can sign on another person’s behalf and that circumstances can change immediately afterward. Educational explanation. Product-specific behavior is scoped to the cited documentation, checked 2026-10-02. Scope: {"collection":"bitcoin","dataAsOf":"2026-10-02","blockHeight":null} ### bitcoin-message-signatures-fact-message-matters Message matters: The exact agreed text is part of verification Scope: {"collection":"bitcoin","dataAsOf":"2026-10-02","blockHeight":null} ### bitcoin-message-signatures-fact-format-matters Format matters: Legacy, simple and full formats differ Scope: {"collection":"bitcoin","dataAsOf":"2026-10-02","blockHeight":null} ### bitcoin-message-signatures-fact-limits Limits: No permanent or exclusive control guarantee Scope: {"collection":"bitcoin","dataAsOf":"2026-10-02","blockHeight":null} ## Sources - [Generic Signed Message Format](https://raw.githubusercontent.com/bitcoin/bips/927b6de9915c9262615a6399de51b200f81e5aa4/bip-0322.mediawiki) — Bitcoin Improvement Proposals. Message-control proof, virtual transactions and limits of supported wallet verification. Locator: Motivation; Types of Signatures; Detailed Specification; Verification Process. Retrieved: 2026-10-02T18:53:54.170Z. ## Revision history - 2026-10-02: First publication after primary-source research and separate automated verification. ## Cite this entry Degrees of Satoshi editorial project. “Bitcoin message signatures: proof of control with clear limits.” Published 2026-10-02; updated 2026-10-02. https://degreesofsatoshi.com/encyclopedia/bitcoin-message-signatures/