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OC Lock

End-to-end encryption addressed to a Bitcoin address. Seal a payload so only the holder of a specific Bitcoin address can open it. No centralized key server, no account, no message broker — the Bitcoin address is the identity and Nostr is the directory.

How it composes

  1. Recipient generates an X25519 device keypair and binds the public key to their Bitcoin address via a BIP-322 signature, then publishes the binding to the Nostr kind-30078 directory.
  2. Sender looks up the recipient's device keys by Bitcoin address, encrypts a payload via X25519 ECDH → HKDF-SHA256 → AES-256-GCM, and wraps the ciphertext in a JSON envelope.
  3. Recipient reads the envelope, decrypts with their device secret, verifies the inner BIP-322 binding, and gets the plaintext.

Anyone can inspect the envelope; only registered device keys can decrypt it. Anyone can verify the sender's BIP-322 signature; no-one can forge it without the sender's key.

What OC Lock IS

  • A protocol for addressing encrypted messages to a Bitcoin address.
  • Non-custodial — no server holds any key material.
  • Permissionless — anyone can publish a device record for their own address; anyone can send an envelope to anyone who has.
  • Offline-verifiable — envelopes are self-contained JSON; no network round-trip required to decrypt.

What OC Lock is NOT

  • A messenger. OC Lock is a protocol; there's no inbox, no threading, no read receipts. Build those on top.
  • A PKI. There's no authority, no revocation list, no trust hierarchy. Revocation is explicit: the recipient publishes a revocation event for a compromised device.
  • A proof-of-personhood. Like OC Attest, OC Lock proves control of a key, not control of a human.
  • Forward secrecy by default. Envelopes use per-recipient ECDH; if a device secret is later compromised, previously-received envelopes can be decrypted. For forward secrecy, rotate device keys frequently.

Section contents

Packages

  • @orangecheck/lock-crypto — narrow crypto primitives (X25519, HKDF, AES-GCM)
  • @orangecheck/lock-core — envelope format, seal(), unseal(), canonicalization
  • @orangecheck/lock-device — device-key management + Nostr directory publication

See SDK overview for the package map.

Shared ecosystem concepts

Read these first if you haven't:

Spec + implementation