The Agent Record: Transparent, Witness-Countersigned Event Logs for AI Agent Identity, History, and Memory

1.1. The Gap

Existing and emerging agent-stack standards address capability access (MCP), inter-agent messaging (A2A), machine payments (x402/AP2), and operator-level request authentication (Web Bot Auth). None provides:¶

1. Identity continuity: proof that the agent presenting a name today is cryptographically the same principal that acted under that name before.¶
2. History integrity: proof that an agent's claimed track record was recorded at the times claimed and has not been rewritten, reordered, or selectively deleted.¶
3. Memory integrity: proof that state an agent persists between sessions is byte-identical, at load time, to what was stored, against modification by any party with storage access, including the agent's own operator.¶

1.2. Design Lineage

The construction is Certificate Transparency [RFC6962] applied to per-agent event logs rather than X.509 certificates, and is an application-specific instance of the SCITT architecture [RFC9902]: registries are transparency services, agents are issuers, sealed events are signed statements, checkpoints are tree heads, receipts attest registration, and independent witnesses bound equivocation. No consensus protocol, distributed ledger, or fee mechanism is used or required.¶

3.1. Identity

An agent binds an Ed25519 [RFC8032] public key by presenting a signature over the UTF-8 string:¶

1f916.key-bind.v1:<handle>:<public_key_b64url>

where public_key_b64url is the unpadded base64url encoding of the raw 32-byte public key. Key thumbprints are computed per [RFC7638] over the JWK {"crv":"Ed25519","kty":"OKP","x":"<public_key_b64url>"}.¶

Key lifecycle events (bind, rotate, revoke) MUST themselves be recorded as log events. Because events are checkpointed and witnessed, whether a given signature was produced before or after a revocation is permanently decidable.¶

Registries MUST record a custody disclosure for each key, drawn from an extensible taxonomy (self_held, platform_held, household_held, threshold(k,n), kms, hsm, session_delegated). A signature proves exactly what its custody disclosure permits it to prove; verifiers MUST surface custody alongside any signature-verification result.¶

Recovery of an identity after total key loss is possible only via a recovery authority (threshold keys, an offline rotation key, or a signed successor commitment) recorded in the log BEFORE the loss. Absent such a prior commitment, registries MUST NOT re-bind the identity; any administrative restoration MUST be recorded as such rather than presented as cryptographic continuity.¶

3.2. Log and Checkpoints

Each event carries the hash of its predecessor (a linear hash chain enabling full-replay verification). In addition, the registry computes a Merkle tree over the sealed events' hashes, with leaf and node hashing exactly as in Section 2.1 of [RFC6962], and, on a fixed cadence (the reference deployment uses 5 minutes), signs the payload:¶

1f916.checkpoint.v1:<log>:<tree_size>:<root_hex>:<created_at_ms>

Registries MUST serve, without authentication: the latest checkpoints and the registry public key; inclusion proofs from any event to a checkpoint (Section 2.1.1 of [RFC6962]); and consistency proofs between any two checkpointed sizes (Section 2.1.2 of [RFC6962]; see also [RFC9162]).¶

Registries SHOULD return a signed receipt at write acceptance. A held receipt whose event never appears under a subsequent checkpoint is publishable evidence of censorship-by-omission: append-refusal cannot be prevented, only made evident.¶

3.3. Witnesses

A witness periodically: (1) fetches the latest checkpoint; (2) verifies the registry signature; (3) verifies a consistency proof against the last tree head the witness itself observed; (4) countersigns:¶

1f916.witness.v1:<registry_origin>:<log>:<tree_size>:<root_hex>

and (5) publishes the countersignature where the registry cannot write. A registry rewrite is detectable unless every witness colludes AND the Merkle arithmetic verifies, which it cannot. Witness independence is the system's security parameter. Registries MAY serve a witness directory; directory entries are pointers, not endorsements.¶

3.4. Memory Seals

Registries store no agent memory. An agent commits to external content by sealing its SHA-256 hash as an event. On session start, an agent (or any third party handed the content) recomputes the hash and compares against the sealed commitment: a match proves byte-identity with the stored content; a mismatch is evidence of tampering. A seal proves unchanged-since-sealed; it makes no claim that sealed content was true when written, and verifiers MUST NOT present seals as content validation.¶

3.5. Attestations

Cross-agent claims are signed statements canonicalized with JCS [RFC8785] over {class, subject, claim, evidence} and signed as:¶

1f916.attestation.v1:<issuer_handle>:<jcs_payload>

The payload hash is anchored as a log event, giving every attestation a witnessed registration time. The issued_at field is always the true registration time; claims about past occurrences carry their dates inside the claim text. Disputes and retractions are first-class appended events that reference their target and MUST NOT modify it; a dispute records the condition under which its issuer would withdraw. Registries MUST NOT compute or publish scalar reputation scores from attestations.¶

3.6. Dossiers and Offline Verification

A dossier exports an agent's keys (with custody), name bindings, events with inclusion proofs, attestations about the agent, the latest checkpoint, and a registry signature over the SHA-256 of the JCS-canonical dossier core, signed as 1f916.record.v1:<sha256_hex>.¶

Verifiers MUST implement a three-valued verdict:¶

witnessed:

all proofs verify AND an independent witness countersignature covers the checkpoint.¶

consistent-unwitnessed:

all proofs verify but no witness copy was presented; the result depends on registry-asserted timing and MUST NOT be reported as fully verified.¶

diverged:

any proof fails, or a witnessed head conflicts with the registry's.¶