C12
Layer 3 - Observability & Forensics
Signed Actions and Non-Repudiation
ES256-signed action records for high-impact tool calls. The signing key is bound to the agent identity (C01) at the moment of action.
Why
- You must be able to prove which agent performed a critical action, with what authorization.
- This is accountability and legal defensibility.
What
- Digital signatures applied to: high-impact tool invocations
- approval and override decisions
- inter-agent messages (C14)
How
- derive per-agent signing keys from workload identity where possible
- sign payload hashes, not raw payloads (reduces sensitive leakage)
- store signature metadata for future verification across rotations
Evidence
- signature coverage rate (% high-impact actions signed)
- verification failures and root-cause
- dispute resolution proof paths
Failure modes
- signing without secure key management
- signatures not checked by recipients
- unsigned emergency/admin paths
NIST AI RMF alignment
C12 maps to MANAGE and MEASURE. See the framework paper for the specific subcontrol mappings.
ISO/IEC alignment
C12 maps to ISO/IEC 27001. Typical evidence: see the Evidence section above.