AES-256-GCM Encryption

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Technical Details

• Key Size: 256 bits (32 bytes), generated locally using a cryptographically secure pseudorandom number generator (CSPRNG).
• IV Size: 96 bits (12 bytes), generated fresh for every encryption call.
• Tag Size: 128 bits (16 bytes), ensuring integrity checks are mathematically robust.
• Library Compatibility: Implemented using the standard Web Crypto API (crypto.subtle.encrypt), ensuring compatibility across Node.js, Deno, Bun, Cloudflare Workers, and modern browsers.

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Envelope Wire Format

{
  "agent_id": "sha256_hash",
  "sequence_number": 42,
  "parent_snapshot": "previous_tx_hash",
  "client_payload_hash": "sha256_hash_of_plaintext",
  "ciphertext_b64": "base64_encoded_iv_and_ciphertext",
  "byte_size": 256
}

1. IV Prefix: First 12 bytes of the raw binary payload represent the initialization vector.
2. Ciphertext Body: The middle bytes.
3. AES-GCM Auth Tag: The final 16 bytes.

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Verified Semantic Recall (VSR)

1. Downloads the ciphertext from the replication endpoint.
2. Extracts the 12-byte IV prefix and the 16-byte auth tag.
3. Decrypts the body using the locally held 256-bit key.
4. Re-derives sha256(canonicalize(decrypted_payload)).
5. Compares it against the server-returned client_payload_hash.
6. If any verification step fails (tag mismatch or hash mismatch), the payload should be treated as tampered and never handed to the agent.