Glossary

SHA-512 — the hash function inside Ed25519

**SHA-512** is a cryptographic hash function from the SHA-2 family producing 512-bit (64-byte) outputs. We use it for the hash step inside Ed25519 signing and for receipt content digests in digest-only mode.
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In Ed25519

Ed25519 internally hashes the signing key and message with SHA-512 to produce the signature nonce. Standard part of the algorithm.

In digest-only receipts

When a project is configured for digest-only mode, the receipt stores SHA-512 hashes of the prompt + response instead of raw text. The hash proves the content existed without storing the content itself.

Why SHA-512 over SHA-256

SHA-512 is what Ed25519 specifies internally. Using the same hash function across the system simplifies the implementation.

Adjacent

See Ed25519, work receipt, content digest, redactPaths.

Related

Ed25519

Elliptic-curve digital signature scheme (RFC 8032). Short signatures, fast verification, strong security.

work receipt

A signed JSON record of AI-mediated work. Ed25519 signature over JCS-canonical JSON.

JCS canonical JSON

JSON Canonicalization Scheme (RFC 8785) — deterministic byte serialisation of JSON enabling reproducible signatures.

content digest

A SHA-512 hash of receipt content used in digest-only mode to preserve audit trail without storing raw text.

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Last reviewed · 2 min read· Open spec· Changelog