# Trust Verdict Evidence Chain (Merkle Proof)

## Module
Attestor

## Status
VERIFIED

## Description
Trust verdict evidence chain built as a Merkle tree for tamper-evident evidence binding, with proofs and evidence ordering for verifiable trust scoring.

## Implementation Details
- **Trust Evidence Merkle Builder**: `src/Attestor/__Libraries/StellaOps.Attestor.TrustVerdict/Evidence/TrustEvidenceMerkleBuilder.cs` (with `.Verify`) -- builds Merkle trees over trust evidence items, providing inclusion proofs and tree-level verification. Implements `ITrustEvidenceMerkleBuilder.cs`.
- **Trust Evidence Merkle Tree**: `Evidence/TrustEvidenceMerkleTree.cs` -- the Merkle tree structure holding evidence nodes with root hash and leaf count.
- **Trust Evidence Merkle Tree Extensions**: `Evidence/TrustEvidenceMerkleTreeExtensions.cs` -- extension methods for tree traversal and proof extraction.
- **Merkle Proof**: `Evidence/MerkleProof.cs` -- inclusion proof for a single evidence item within the trust evidence Merkle tree.
- **Trust Evidence Ordering**: `Evidence/TrustEvidenceOrdering.cs` -- deterministic ordering of evidence items before tree construction to ensure reproducible root hashes.
- **Trust Evidence Chain Predicate**: `Predicates/TrustEvidenceChain.cs` -- predicate model containing the ordered list of evidence items and the Merkle root binding them.
- **Trust Evidence Item**: `Predicates/TrustEvidenceItem.cs` -- individual evidence item (origin verification, freshness, reputation) included in the chain.
- **Trust Verdict Predicate**: `Predicates/TrustVerdictPredicate.cs` -- the overall trust verdict that references the evidence chain Merkle root.
- **Trust Verdict Service**: `Services/TrustVerdictService.cs` (with `.BuildPredicate`, `.Builders`, `.Generate`, `.Scoring`) -- orchestrates evidence collection, chain building, and verdict generation.
- **Tests**: `__Tests/StellaOps.Attestor.TrustVerdict.Tests/`

## E2E Test Plan
- [ ] Build a trust evidence chain via `TrustEvidenceMerkleBuilder` with 5 evidence items and verify the Merkle root is deterministic across repeated builds
- [ ] Generate an inclusion proof for a specific evidence item via `TrustEvidenceMerkleBuilder` and verify it against the Merkle root via `.Verify`
- [ ] Verify evidence ordering: create evidence items in random order, build two chains, and confirm identical Merkle roots due to `TrustEvidenceOrdering`
- [ ] Generate a full trust verdict via `TrustVerdictService.Generate` and verify `TrustVerdictPredicate` contains the evidence chain Merkle root
- [ ] Tamper with one evidence item after chain construction and verify the Merkle proof fails validation
- [ ] Build a chain with a single evidence item and verify the Merkle root equals the leaf hash
- [ ] Verify the `TrustEvidenceChain` predicate serializes to JSON with ordered evidence items and Merkle root
- [ ] Build a large chain (100+ items) and verify proof verification completes in under 50ms

## Verification

| Check | Result |
|-------|--------|
| Tier 0 - Source Verification | PASS |
| Tier 1 - Build + Code Review | PASS |
| Tier 2 - Behavioral Verification | PASS |
| Verified Date | 2026-02-13 |
| Run ID | run-001 |