# Chain of custody — NADIR Evidence Vehicle Bundles (EVB)

**Web page:** https://nadirai.net/trust/evidence  
**Full playbook:** https://nadirai.net/guides/credibility-playbook  
**API:** `GET /v1/evidence/bundles/{bundle_id}` · `POST /v1/evidence/export`  
**Sample ID:** `EVB-20260603-B7F2`

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## What is an EVB?

An **Evidence Vehicle Bundle** is a signed JSON document that captures:

1. **Drift timeline** — tier transitions with timestamps and residual confidence
2. **Validation pass** — post-calibration residual measurements
3. **Sensor graph** — which modalities contributed (camera, radar, fusion)
4. **Chain of custody** — ingest → score → changepoint → validation → sign
5. **Cryptographic signature** — Ed25519 over canonical payload hash

## Custody stages

```
INGEST → ALIGN → SCORE → CHANGEPOINT → VALIDATE → SIGN → EXPORT
```

| Stage | NADIR component | Audit artifact |
|-------|-----------------|--------------|
| Ingest | `/v1/telemetry/ingest` | Raw frame IDs + ingest receipt |
| Align | Temporal alignment bus | Sync offset metadata |
| Score | Residual + tier engine | Tier + confidence per timestamp |
| Changepoint | BOCPD / HSMM gates | Changepoint event ID |
| Validate | Calibration lab parity | Post-repair residual ≤ threshold |
| Sign | Evidence signing service | `signature` + `signing_key_id` |
| Export | Evidence Theater / API | Downloadable EVB JSON |

## Who uses EVBs?

| Buyer | Use case |
|-------|----------|
| **Fleet safety** | Prove calibration was valid before incident |
| **Insurer / DRP** | Subrogation and claims QA |
| **MSO QA** | Attach to work order at structural release |
| **OEM auditor** | Validation program traceability |

## Verification

1. Download EVB from HORIZON Evidence Theater or API
2. Verify `payload_hash` matches canonical JSON (sorted keys)
3. Verify `signature` against NADIR published key (`signing_key_id`)
4. Cross-check `vehicle_id` and timestamps against telematics export

## Related pages

- Product evidence overview: `/evidence`
- MSO solution: `/solutions/mso-evidence`
- API reference: `/api`
- HORIZON Theater: `/pilots/horizon#module-theater`

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*Not legal advice. Counsel review required for contractual evidence obligations.*