Audit Chain

Every proxy action is logged to an append-only, tamper-evident audit chain.

Format

JSONL (JSON Lines). One entry per line.

{"seq":1,"ts":"2024-01-15T10:30:00Z","cap":"openai-chat","action":"request","outcome":"allowed","hash":"abc...","prev":"000...","sig":"def..."}
{"seq":2,"ts":"2024-01-15T10:30:01Z","cap":"openai-chat","action":"response","outcome":"success","hash":"ghi...","prev":"abc...","sig":"jkl..."}

Entry Fields

Field	Description
`seq`	Sequence number, monotonically increasing
`ts`	ISO 8601 timestamp
`cap`	Capability name
`action`	`request`, `response`, `blocked`, `error`
`outcome`	Result: `allowed`, `denied`, `rate_limited`, `taint_blocked`, etc.
`hash`	SHA-256 hash of this entry (excluding `hash` and `sig`)
`prev`	Hash of previous entry (chain link)
`sig`	Ed25519 signature of `hash`

Integrity Properties

Hash Chain

Each entry's prev field contains the previous entry's hash. Tampering with any entry breaks the chain.

Entry 1          Entry 2          Entry 3
┌──────┐        ┌──────┐        ┌──────┐
│hash_1│◄───────│prev  │◄───────│prev  │
└──────┘        │hash_2│        │hash_3│
                └──────┘        └──────┘

Signatures

Each entry is signed with an Ed25519 private key. The corresponding public key can be used to verify authenticity.

Verification

To verify an audit log:

Check each entry's hash matches SHA-256 of entry content
Check each entry's prev matches previous entry's hash
Verify Ed25519 sig against hash using public key
Check seq is monotonically increasing
Check ts is monotonically increasing (within tolerance)

Storage

Default path: /var/log/hull0/audit.jsonl

Configurable via manifest settings.audit_path.

Compliance

The audit chain provides:

Non-repudiation (signatures)
Tamper evidence (hash chain)
Completeness (sequence numbers)
Temporal ordering (timestamps)

Suitable for SOX, HIPAA, GDPR audit requirements.

Hull0