Etch vs Sigstore Rekor
Sigstore Rekor is a transparency log for software artifacts. Etch is a per-project signed decision chain for AI agents. They compose. This page names how and where.
Different lanes
Rekor is optimized for one job: give the community a public, append-only, cryptographically walkable record of signed software artifacts. It is deliberately schema-agnostic. Every entry is a signed digest with metadata; the semantic layer is whatever the client puts there.
Etch is optimized for the layer above. Every event on an Etch
chain is a typed agent decision (refused_call,
assumption_declared, discharge_access,
control_lifecycle) with a specific framework
mapping (SR 11-7, EU AI Act Article 12, ISO 42001, NIST AI
RMF). Etch stores that domain model directly on its chain and
anchors each closed epoch's Merkle root into Rekor so the epoch
commitments inherit Rekor's public transparency.
Where they compose
Rekor as public time anchor
Etch pushes every closed epoch's Merkle root into Rekor with an ECDSA-P256 signature. An auditor walking an Etch chain independently verifies that anchor in Rekor without trusting Etch.
Etch as the semantic layer
Etch adds typed agent events, framework mapping, and reference OSS verifier. Rekor entries alone cannot answer "which policy version did the reviewer apply." Etch can.
Reader trust story
The reader trusts Rekor for time and public witnesses. The reader trusts Etch's pinned public keys for authenticity. Failure of either layer does not silently invalidate the other; both are checked at verify.
Frequently asked
Is Etch a competitor to Sigstore Rekor?
No. Etch composes with Rekor. Etch is a per-project decision chain for AI agent events; Rekor is a transparency log for software artifacts. Etch anchors every closed epoch's Merkle root onto Rekor so the epoch commitments carry a public, auditor-verifiable time anchor that does not depend on Etch staying online.
What does Rekor give me that Etch does not?
Rekor is a public, community-run transparency log with a Ken-Thompson-style operator-independent trust story. Etch does not replace that. Etch pushes its epoch anchors into Rekor precisely so a reader of an Etch chain can independently verify the epoch anchor exists in Rekor at the time claimed.
What does Etch give me that Rekor does not?
A domain-specific semantic layer for AI agent governance. Rekor logs artifacts; Etch logs agent events with typed kinds (refused_call, assumption_declared, discharge_access, control_lifecycle, silent_control_failures, dimensional_drift, cross_chain_reference). Etch also provides framework mapping to SR 11-7, EU AI Act Article 12, ISO 42001, and NIST AI RMF that Rekor is not designed to model.
Can I use Rekor alone for AI audit trails?
Only if you write and maintain your own AI-specific schema on top of Rekor entries. Rekor stores signed artifact digests; the semantic layer (whose decision, which policy, which framework section) is on you. Etch delivers that semantic layer as a product with framework mapping already wired in.
Do I need to run my own Rekor instance to use Etch?
No. Etch anchors epochs into the public Sigstore Rekor community instance by default. Enterprise customers who require a private Rekor for legal or network-partition reasons can point Etch at a self-hosted Rekor via configuration.