# Evidence Locker Attestation Contract (v1 · frozen 2025-11-20)

Scope: Evidence Bundle v1 produced by Evidence Locker and consumed by Concelier, Excititor, Export Center, CLI, and Policy Engine.

## Predicates & subjects
- **Subject (mandatory):** Merkle root derived from `checksums.txt` (sha256 of the sorted file) for the sealed bundle. OCI digest of the tarball remains recorded as `bundle_oci_digest` inside the predicate for registry mirroring but is not the DSSE subject.
- **Predicates (DSSE/In-Toto)**
  - `stellaops.evidence.bundle.v1`: declares bundle layout (manifests, CAS paths, replay log offsets, Merkle recipe, chunking strategy).
  - `stellaops.evidence.transparency.v1`: Rekor/log inclusion proof (UUID, log index, root hash at inclusion). Required when network-permitted; when offline, include `reason="offline"` and omit log pointers.
  - `stellaops.evidence.integrity.v1`: hashes for each payload (SBOMs, VEX, policy packs, telemetry snapshots), keyed by canonical path; must match entries in `bundle.manifest.schema.json`.

## Required claim set
- `bundle_id` (UUID v4)
- `produced_at` (UTC ISO-8601)
- `producer` (`evidence-locker:<region>`)
- `subject_merkle_root` (sha256 from checksums.txt)
- `hashes` (map: canonicalPath → sha256) sorted lexicographically
- `sbom` (array of SPDX/CycloneDX digests and mediaTypes)
- `vex` (array of VEX doc digests and schema versions)
- `replay_manifest` (optional; digest + sequence number, ledger URI, dsseEnvelope)
- `transparency` (optional; Rekor UUID, logIndex, rootHash, inclusionProof) or `reason="offline"`
- `signing_profile` (`sovereign-default` | `fips` | `gost` | `pq-experimental`)

## Bundling & signing rules
- DSSE envelope is **mandatory** for every sealed bundle using the configured `ICryptoProviderRegistry` profile; keys must be short-lived (<24h) and recorded in provider registry.
- Subject = sha256(Merkle root) from `checksums.txt`; verifier must recompute to match.
- Hash list must match `bundle.manifest.schema.json` (entries + optional `hashSummary`), sorted by `canonicalPath`.
- Rekor/logging policy:
  - If outbound log is allowed, submit to configured log and embed UUID/logIndex/rootHash in `transparency`.
  - If outbound log is disallowed/offline, set `transparency` to null and include `reason="offline"` plus `log_policy="skip"` inside the predicate.

## Verification plan
- Verify DSSE signature against provider registry (per profile) and check key expiry.
- Recompute sha256 for every manifest entry and the Merkle root; fail if subject differs.
- If `transparency` present, verify inclusion proof against bundled Rekor root; fail closed on mismatch. If absent, require `reason="offline"` and `log_policy="skip"`.
- Emit verification report JSON (deterministic key order) and store beside bundle as `verify.json`.

## Fixtures
- Sample bundle + report: `docs/samples/evidence-locker/bundle-v1-sample.tar.gz` (sha256 TBD at publish time).
- Sample attestation envelope: `docs/samples/evidence-locker/attestation-v1-sample.json`.

## Ownership
- Primary: Evidence Locker Guild.
- Reviewers: Concelier Core Guild, Excititor Guild, Export Center Guild, Policy Guild.

This contract is authoritative for Sprint 110 and blocks CONCELIER-ATTEST-73-001/002 and EXCITITOR-ATTEST-01-003/73-001/73-002.