offline-protocol-leaf
A constrained device that speaks the Offline Protocol as a real peer: a door lock, a sensor, a mains-powered relay. It parses frames, validates addressing, runs RFC 9420 MLS through mls-rs, and holds an end-to-end encrypted conversation with a phone under the same guarantees a phone gets. Same frames, same envelope, same trust gates, no second sealing path.
Provides:
LeafDevice, a frame-level state machine: hand it an inbound message, get back the frames to send and what happened- The never-committing member profile, where the phone creates the group and issues every commit and the device joins, opens, answers and persists
LeafStore, one blob-storage seam a device implements over its secure key storage, with persist-before-emit enforced rather than documented- Key package minting with the backdated
not_beforeand supplied timestamp a device needs to pair at all
Four obligations this crate cannot discharge for you: a time source at pairing (every entry point takes now_unix_secs, because a device that lets an MLS library read a clock it does not have stamps 1970 and is refused as expired), real entropy (this crate registers no getrandom backend on purpose; wire the symbol to the part's hardware source), durable storage (LeafStore must be atomic per entry, because a ratchet state rolled back by a power cut reuses an AEAD nonce), and authorization (a session proves who a peer is and never that the owner meant them, since any address in radio range can complete a pairing, so firmware decides when the radio accepts one and what a given peer may actuate).
Like offline-protocol-core and offline-protocol-sealed, this crate compiles for bare-metal targets with --no-default-features (add --features bare-metal-rng).
This crate is for firmware. Applications on a phone want the main offline-protocol crate instead, or the React Native or Python bindings.
License
Copyright © 2025-2026 Offline Protocol, Inc.
Dual-licensed: AGPL-3.0-only for open-source use, or a commercial license for proprietary use.