RFC 8785 JCS canonicalization + ES256 signing implementation #1
Description
Summary
Implement the actual signing and verification logic. Currently write-only — attestations can be created but not verified.
Requirements
- RFC 8785 (JSON Canonicalization Scheme) implementation for deterministic payload serialization
- ES256 signing:
signature.value = ES256(SHA-256(JCS(payload))) verify_signature()function in all three languages (Rust, Python, TypeScript)- Canonical payload builder that extracts the signable fields from an IntegrityAttestation
- Timestamp validation (ISO 8601 format, not in future, max age enforcement)
Blocking
This blocks all signed attestation work (Phase 2+). Without canonicalization, cross-language verification breaks.
References
- RFC 8785
- docs/ATTESTATION.md — Canonicalization section