Mii crypto spec

Mobius Integrity Index (MII) — Cryptographic Spec v0.1¶

Goal: verifiable, replay-safe attestations that bind (service_state, metrics, time) to a signer.

Signature¶

• Algorithm: Ed25519 (libsodium/NaCl)
• Key material: 32-byte seed, 64-byte expanded secret key

Signing Payload¶

Canonical JSON (UTF-8, SHA-256 preimage):

{
  "service_id": "ledger-api",
  "instance": "ledger-api-01.us-east-1",
  "mii": 0.9734,
  "mii_window": {"from":"2025-11-08T06:00:00Z","to":"2025-11-08T07:00:00Z"},
  "gi_components": {
    "accuracy":0.991,"consistency":0.982,"fairness":0.965,"entropy":0.978
  },
  "nonce": "base64(16B)",
  "prev_attestation_hash": "hex(SHA-256)",
  "issued_at": "2025-11-08T07:05:00Z",
  "expires_at":"2025-11-08T07:20:00Z",
  "schema":"https://mobius/specs/attestation@v0.1"
}

Signature Process¶

1. Canonicalize payload (stable key order, no whitespace).
2. Hash with SHA-256; use hex digest as Ed25519 message.
3. signature = base64(Ed25519.sign(digest, secret_key))
4. Attach kid referencing rotating JWKS entry.

Key Distribution & Rotation¶

• JWKS hosted at /.well-known/mobius/jwks.json
• Key IDs rotate every 30 days (or on compromise).
• Historical keys kept for 90 days to verify delayed attestations.

Replay & Expiry Controls¶

• Nonce: base64-encoded 16-byte random value.
• Window: mii_window.from/to (15-minute cadence).
• prev_attestation_hash: links attestations into a hash chain.
• expires_at: reject attestations older than 15 minutes.

Revocation¶

• Publish CRL at /.well-known/mobius/attestations/crl.json.
• Ledger marks revoked attestations and issues compensating entries.