AER-1 and SCITT: The Carriage, Field by Field
SCITT (Supply Chain Integrity, Transparency and Trust) is the IETF working group building transparency services: registries that take a statement from an issuer, record it, and return an inclusion proof anyone can check later. AER-1 is a receipt format for agent tool calls. The two compose, and AER-1 says so in its own text: since draft -18, and in the current draft-zambo-aer1-26, a receipt's external anchor can be of type "scitt", which means the receipt's digest was registered with a SCITT Transparency Service and the service's inclusion proof travels with the receipt. This page maps that carriage from Section 10 of the draft, then sets AER-1 beside the other receipt formats now published as Internet-Drafts, limited to what each draft claims for itself. The companion concept page, AER-1 and SCITT: how they fit together, covers why the two designs meet at this point.
The carriage, from Section 10 of draft-zambo-aer1-26
| Element | What the draft defines |
|---|---|
| anchored_digest | The digest being anchored: for a single receipt, its output digest; for a job timeline, the final entry digest of the chain commitment (Section 7.3); the exact value depends on the record's merkle_version (Section 8.1). |
| anchor_type | One of "nostr", "ots", "witness", "scitt" or "rfc3161". The anchor is optional; a receipt with no anchor still verifies by recompute. |
| anchored_at | An RFC 3339 timestamp of when the anchor was published. |
| proof.service | For anchor_type "scitt": the URL of the SCITT Transparency Service with which the anchored_digest was registered as the payload digest of a Signed Statement (RFC 9943). |
| proof.cose_receipt | A base64-encoded COSE receipt: the inclusion proof the service returned for that registration. |
Verification of a "scitt" anchor, as the draft states it: verify the COSE receipt against the Transparency Service's published key, and confirm the registered statement's payload digest equals the receipt's anchored_digest. Report the anchor as verified only when both hold. Core AER-1 verification neither requires nor is changed by the registration: the recompute over the saved result stands on its own, and the anchor adds an outside witness to when the digest existed.
The receipt drafts, side by side
Each row is limited to what the named work states about itself in its published draft or reference material. Formats differ in what they record and where the record lives; none of the rows below is a ranking.
| Format | What it records | Where the record lives |
|---|---|---|
| AER-1 (draft-zambo-aer1-26) | One receipt per agent tool call: the tool, the input record, the saved result and its SHA-256 digest, with optional external anchors including the SCITT carriage above. Workflow records bind a job's receipts in sequence. | Each receipt resolves at a stable public URL; verification is a public recompute endpoint, and a conformance corpus (126 vectors, 129 checks) lets independent implementations check they read receipts the same way. |
| Sijil execution evidence (draft-thaha-scitt-agent-execution-evidence) | A hash-chained record of agent calls, carried as SCITT statements. | Registered with a SCITT Transparency Service; ships with an offline verifier and an Apache-2.0 prototype. |
| SCITT AI agent execution profile (draft-emirdag-scitt-ai-agent-execution-00) | An AgentInteractionRecord carried as the payload of a COSE envelope; the profile maps its records to EU AI Act Articles 12 and 19, DORA and the NIST AI RMF. | Registered with a SCITT Transparency Service. |
| ACTA (draft-farley-acta) | Decision receipts: records of an agent's decisions, produced by a proxy in the call path (the protect-mcp reference implementation is an MCP stdio proxy). | Held by the proxy's operator; the draft defines the receipt format. |
| AgentROA | Agent Enforcement Receipts: records aimed at enforcement points, written for SCITT logs. | SCITT transparency logs. |
| Attested Intelligence | Receipts for every MCP tool call, issued by a governance proxy in the call path, each carrying an Ed25519 signature from the proxy. | Held by the proxy's operator. |
Where interop stands, honestly
The formats above were written independently, and no two of them yet read each other's receipts natively. The working connection today is the one the drafts themselves define: a digest from any of these records can be registered as a SCITT statement, and AER-1's anchor object is one published way to carry the resulting proof next to the record it witnesses. The survey literature has begun cataloguing the field (the arXiv paper "Notarized Agents" reads the receipt drafts together), and AER-1's own reference list already cites a SCITT-carried agent receipt draft (draft-noa-scitt-ai-agent-receipt-01) and a delegation-receipts draft (draft-nelson-agent-delegation-receipts-14). A public interop matrix, where each implementation verifies the others' records and publishes the results, is the obvious next step; it has not happened yet, and this page will say so until it has.
Sources
- Internet-Draft draft-zambo-aer1-26, Section 10 (external anchors) and the anchor verification rules: datatracker.ietf.org/doc/draft-zambo-aer1/
- RFC 9943, SCITT Architecture; the SCITT working group drafts named in the table: datatracker.ietf.org/wg/scitt/
- The public verifier: zambo.dev/verify. The endpoint: zambo.dev/mcp.
Related: AER-1 and SCITT: how they fit together · OWASP Agentic Top 10 duties, mapped onto AER-1 · EU AI Act Article 12, mapped onto AER-1