Proof and Signing

Bridge Kernel converts raw adapter events into signed ProofEnvelope records.

EventEnvelope

The normalized event before signing, produced by the adapter + runtime normalization path.

ProofEnvelope fields

• event
• key_id
• key_version
• signature_context
• signer_public_key_hex
• payload_hash_hex
• signature_hex
• signed_at

Canonical JSON rules

• Sorted keys
• No extra whitespace
• UTF-8 bytes

Deterministic serialization ensures two nodes hash the same event bytes identically.

Hashing

SHA-256 is computed over canonical JSON bytes and stored as payload_hash_hex.

Signing

Ed25519 signs canonical payload bytes (or equivalent deterministic digest contract) through HAL abstraction.

Verification flow

1. Rebuild canonical bytes.
2. Recompute SHA-256 hash.
3. Compare computed hash to payload_hash_hex.
4. Verify Ed25519 signature using embedded public key and signature_context.

HAL options

• SoftwareHal: software keypair in keystore.
• TpmHal: hardware-backed signing path for strict environments.

Failure handling

• Canonical mismatch: reject and log proof mismatch reason.
• Hash mismatch: reject as tamper-evident failure.
• Signature mismatch: reject and isolate source for triage.
• Unknown key version: reject until key metadata is refreshed.