Ember

End-to-end encrypted messenger that works during network outages, over intermittent connections, and across constrained transports like LoRa or BLE. No session state, no prekeys, no central server required.

An ember glows quietly, surviving long after the flame has gone out. When instant messaging systems go dark, Ember keeps messages alive - waiting patiently to deliver them when connectivity returns.

🚧 Experimental. Most of the code, tests, and documentation were written by AI (Claude Code, Codex, GitHub Copilot, OpenCode). Humans direct architecture and design decisions but have not reviewed most code line-by-line. There will be bugs. Use at your own risk.

Features

• Stateless encryption - no session keys or prekeys. Messages work independently, even if delivered out of order or months late.
• Multiple transports - HTTP mailboxes, MQTT broadcast, mDNS/LAN direct P2P. LoRa, Meshtastic, and BLE planned.
• LAN discovery - finds and verifies peers on local networks automatically via mDNS.
• Sneakernet - export/import .ember bundles for air-gapped message transfer.
• Delay-tolerant by default - every design decision favors eventual delivery over low latency.

Status (v0.5)

Proof-of-concept. Working:

• Stateless encryption (MIK-based, similar to Session V1)
• HTTP mailbox transport with pagination
• MQTT broadcast transport
• mDNS/LAN peer discovery with identity verification
• Multi-transport delivery with outbox retry
• Merkle DAG message ordering
• Delivery receipts and cache clearing (tombstones)
• Sneakernet bundle export/import
• TUI client with embedded relay

See ROADMAP.md for what's next and WHITEPAPER.md for the protocol spec.

Quick start

Requires Rust 1.75+.

git clone https://github.com/leon0399/ember.git
cd ember
cargo build --release

Start a mailbox node and two clients in separate terminals:

cargo run --bin node -- --port 3000

cargo run --bin client   # Alice

cargo run --bin client   # Bob

In the TUI: create an identity, add the other user's Public ID as a contact, and send a message. Messages route through the local mailbox at http://127.0.0.1:3000.

LAN discovery

If both clients have the embedded relay enabled and are on the same network:

1. Set lan_discovery.enabled = true in config
2. Set embedded_node.http_bind = "0.0.0.0:0" (random port)
3. Restart - clients discover each other via mDNS and send messages directly, bypassing the mailbox

Architecture

Rust workspace with focused crates (ember-identity, ember-encryption, ember-transport, etc.) and two binaries:

• client - TUI (ratatui) with embedded relay
• node - standalone mailbox server (Axum)

Configuration

Both binaries use layered config: CLI args > env vars > config file > defaults.

• Client: ~/.config/ember/config.toml, env prefix EMBER_*
• Node: ~/.config/ember/node.toml, env prefix EMBER_NODE_*

See apps/client/config.example.toml and apps/node/config.example.toml for all options.

Documentation

• WHITEPAPER.md - protocol spec, cryptography, wire format
• ROADMAP.md - release timeline and feature planning
• docs/threat-model.md - attack scenarios and mitigations
• docs/tiered-delivery.md - delivery system design
• docs/lan-discovery.md - mDNS peer discovery

Security

No forward secrecy in v0.5. Ember uses stateless encryption to tolerate arbitrary message delay and reordering. If a user's key is compromised, all their past messages are exposed. This is a deliberate tradeoff; forward secrecy is planned for v0.7.

Messages are end-to-end encrypted and authenticated. Relays never see plaintext. See docs/threat-model.md for details.

Development

cargo test --workspace --all-features --all-targets
cargo fmt --all -- --check
cargo clippy --all-targets --all-features -- -D warnings
cargo deny check

License

GPL-3.0-or-later. See LICENSE.

Acknowledgments

Ember draws on ideas from Session (stateless encryption), Briar (DTN messaging), Meshtastic (LoRa mesh), Nostr (relay architecture), and the Signal Protocol (studied but not adopted due to DTN incompatibility).

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