Signature Hash

Overview

Signature systems usually transform structured data into a canonical byte representation and cryptographic digest before signing. In blockchain transactions, signature-hash rules determine which fields, inputs, outputs, amounts, or conditions the signer actually commits to.

Different signature-hash modes can intentionally leave parts changeable, enabling specialized workflows but also creating misuse risk. Ambiguous serialization, missing domain separation, hash collisions, or incorrect field inclusion can authorize unintended transactions.

Implementations should use exact protocol rules, canonical encoding, reviewed libraries, explicit network and domain binding, and clear signer displays. Tests should cover every mode, boundary case, version, and interaction with hardware wallets, multisignature, fee changes, and transaction replacement. Specification changes should preserve test vectors and compatibility expectations across every supported signer.

For Signature Hash, production scope should name the relevant keys, signing policies, accounts, addresses, transactions, recovery paths, and custody boundaries, the decision being supported, the accountable owner, and the time and jurisdiction boundaries.

A signature hash is the digest or signing preimage derived from transaction or message data and then authorized by a digital signature. The signature hash defines the authorization boundary, so every included, excluded, encoded, and domain-bound field must be understood precisely.

A production treatment of Signature Hash should test the digest or signing preimage derived from transaction or message data and then authorized by a digital signature within the relevant asset, decision, or service state. The Signature Hash context record for digest, and signing preimage derived from transaction should preserve source data, configuration or policy version, responsible actor, exception, and outcome. Review of Signature Hash should determine whether safeguards addressing digest, and signing preimage derived from transaction changed exposure in practice, not merely whether a document or setting existed.