ECP Specification

The full Evidence Chain Protocol specification is maintained in the main repository:

📄 ECP-SPEC.md on GitHub

Version

Current: ECP-SPEC v2.1

Summary

ECP defines a 5-level progressive evidence model:

Level	Name	What's Recorded	Integrity
1	Minimal	input/output hashes only	Hash
2	Standard	+ model, latency, tokens, cost	Hash
3	Signed	+ Ed25519 signature	Hash + Sig
4	Chained	+ linked to previous record	Hash + Sig + Chain
5	Anchored	+ Merkle root on-chain (EAS)	Hash + Sig + Chain + Blockchain

Data Format

Record (Nested Format — Python SDK)

{
  "ecp": "0.1",
  "id": "rec_xxx",
  "agent": "did:ecp:xxx",
  "ts": 1711180800000,
  "step": {
    "type": "llm_call",
    "in_hash": "sha256:...",
    "out_hash": "sha256:...",
    "latency_ms": 1200,
    "model": "gpt-4",
    "flags": []
  },
  "chain": { "prev": "sha256:...", "hash": "sha256:..." },
  "sig": "ed25519:..."
}

Record (Flat Format — TypeScript SDK)

{
  "id": "rec_xxx",
  "agent": "did:ecp:xxx",
  "ts": 1711180800000,
  "action": "llm_call",
  "in_hash": "sha256:...",
  "out_hash": "sha256:...",
  "latency_ms": 1200,
  "model": "gpt-4",
  "flags": [],
  "chain": { "prev": "sha256:...", "hash": "sha256:..." },
  "sig": "..."
}

Both formats are valid. Chain hash is computed over the canonical JSON of the record (with chain.hash="" and sig="").

Cross-SDK Hash Interoperability

Given identical JSON structure, Python and TypeScript produce identical chain hashes:

• Python: json.dumps(obj, sort_keys=True, ensure_ascii=False, separators=(",",":"))
• TypeScript: stableStringify(obj) — recursive key sort, no spaces

Verified: 14/14 interop tests passing (SHA-256, chain hash, Merkle root).