# VEX Integration with Proof-Carrying Verdicts

## Module
Attestor

## Status
VERIFIED

## Description
VEX verdicts carry cryptographic proof references (proof_ref, proof_method, proof_confidence, evidence_summary). ProofAwareVexGenerator in Scanner orchestrates end-to-end flow: scanner detects CVE, BackportProofService generates proof, VexProofIntegrator embeds proof metadata in VEX verdict.

## Implementation Details
- **VEX Proof Integrator**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Generators/VexProofIntegrator.cs` (with `.Helpers`, `.Metadata`) -- embeds proof metadata (proof_ref, proof_method, proof_confidence) into VEX verdicts, linking verdicts to cryptographic evidence.
- **VEX Verdict Proof Payload**: `Generators/VexVerdictProofPayload.cs` -- payload containing the VEX verdict with embedded proof references and evidence summary.
- **Backport Proof Generator**: `Generators/BackportProofGenerator.cs` (with `.CombineEvidence`, `.Confidence`, `.Status`, `.Tier1`, `.Tier2`, `.Tier3`, `.Tier3Signature`, `.Tier4`, `.VulnerableUnknown`) -- generates multi-tier confidence-scored backport proofs that are referenced by VEX verdicts.
- **Evidence Summary**: `Generators/EvidenceSummary.cs` -- summary of evidence items supporting the VEX verdict (proof count, confidence range, evidence types).
- **VEX Attestation Predicate**: `Predicates/VexAttestationPredicate.cs` -- attestation predicate with proof-carrying verdict data.
- **VEX Verdict Summary**: `Predicates/VexVerdictSummary.cs` -- summary of proof-carrying VEX verdicts.
- **VEX Verdict ID**: `Identifiers/VexVerdictId.cs` -- content-addressed ID for the proof-carrying verdict.
- **Binary Fingerprint Evidence Generator**: `Generators/BinaryFingerprintEvidenceGenerator.cs` (with `.Helpers`) -- generates binary fingerprint evidence used as proof for VEX verdicts.
- **VEX Verdict Statement**: `Statements/VexVerdictStatement.cs` -- in-toto statement wrapping the proof-carrying verdict.
- **Tests**: `__Tests/StellaOps.Attestor.ProofChain.Tests/`

## E2E Test Plan
- [ ] Generate a backport proof via `BackportProofGenerator.Tier1` (exact version match) with confidence 0.98 and verify the proof payload is created
- [ ] Embed the proof into a VEX verdict via `VexProofIntegrator` and verify the verdict contains proof_ref, proof_method="backport_tier1", and proof_confidence=0.98
- [ ] Generate a Tier3 proof (signature-based) and embed in VEX; verify proof_method="backport_tier3_signature" and confidence range 0.80-0.90
- [ ] Verify `EvidenceSummary` reports correct counts: create a verdict with 3 evidence items and verify the summary has count=3
- [ ] Create a proof-carrying VEX verdict for a not_affected CVE and verify the proof_ref points to a valid content-addressed proof bundle
- [ ] Generate a `VexVerdictId` from the proof-carrying verdict and verify it is deterministic
- [ ] Build a `VexVerdictStatement` with proof references and verify it is a valid in-toto statement
- [ ] Create a VEX verdict without proof and verify proof_ref is null, proof_confidence is 0, indicating no proof backing

## 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 |