Off-Grid Messaging

Pairs with Overview - Off-Grid Networks (transport layer) and Overview - Encrypted Messaging (security model).

Why it matters

The internet has many choke points: ISPs, cloud providers, CAs, governments. Off-grid messaging assumes those have failed (by censorship, infrastructure damage, or power loss) and asks whether people can still communicate.

Threats addressed:

• Internet shutdowns (Iran, Belarus, Cuba, Myanmar — recurring).
• Disaster scenarios where centralized infrastructure is offline.
• Surveillance environments where any internet contact is logged.
• Physical occupation where the only safe channel is short-range.

Approach families

1. LoRa Mesh (Meshtastic)

LoRa radios on 868 / 915 MHz ISM bands provide kilometers of range at low bandwidth. Meshtastic firmware turns devices into a self-organizing mesh:

• Range: 1-10 km line-of-sight, 30+ km from elevation.
• Throughput: 100-1500 bytes/sec depending on settings.
• Power: multi-day battery; solar-friendly.
• Crypto: AES-256 channel encryption (shared key per channel).

Use cases: hiking groups, neighborhood resilience networks, festival comms, emergency channels. It doesn't replace the internet; it provides a graceful-degradation channel when the internet is gone.

2. Reticulum + LXMF

Reticulum is a generic encrypted-by-default mesh networking stack (Markqvist) supporting LoRa, packet radio, TCP, serial. LXMF is its message format. It's like email but built on Reticulum's identity model, where each user is a public key.

Properties:

• End-to-end encrypted (Curve25519 + AES) by stack design.
• Store-and-forward: propagating nodes hold messages until the recipient is reachable.
• Identity is the key, the same as Tor v3, Nostr, PKARR.
• Heterogeneous transport: runs over anything that delivers bytes.

Tooling: NomadNet (terminal UI), Sideband (cross-platform messenger), MeshChat.

3. Briar (P2P over Bluetooth / Wi-Fi / Tor)

Designed for activists and journalists in adversarial conditions. Three transports:

• Bluetooth: short-range, no infrastructure, no logs.
• Wi-Fi direct / hotspot: faster, slightly longer range.
• Tor onion services: when the internet exists.

The same client uses all three transparently. A user can switch between modes as the threat environment changes. Briar Mailbox lets messages queue while peers are offline.

4. Bluetooth-mesh apps

• Bitchat: modern BLE mesh from Permissionlesstech with Nostr fallback. Phone-only, multi-hop (up to 7), Noise-encrypted. iOS / macOS / Android. See Bitchat.
• Bridgefy: Bluetooth mesh; used in protests in Hong Kong (2019) and Belarus (2020). Cryptographic concerns surfaced in 2020 audits; updated since.
• AirChat / Apple Find My abuse: research projects using Bluetooth advertising for opportunistic tiny messages.

5. Long-range HF / packet radio

• JS8Call: keyboard-to-keyboard chat over HF radio (3-30 MHz). Truly intercontinental, very low bandwidth.
• AX.25 packet radio: legacy ham digital mode; slow but survives anything.
• Reticulum over HF: emerging, combines RNS encryption with HF range.

Requires an amateur radio license in most jurisdictions for legal operation; the threshold model in extremis differs.

Comparing range vs throughput

Threat model considerations

Off-grid messaging has different threats from internet-based messaging:

• Direction-finding (DF). Active radios are locatable. LoRa transmissions can be triangulated. Mitigations: low duty cycle, mobile transmitters, secure-by-design protocols that don't disclose source until needed.
• Capture of nodes. Physical compromise reveals stored messages and keys. Mitigations: encrypted storage, ephemeral keys, no message history retention (Briar's default).
• Mesh-flood DoS. Spam in a low-bandwidth mesh saturates it. Mitigations: rate limiting, proof-of-work, paid-relay variants.
• Sybil at the routing layer. Adversary floods mesh with fake nodes to deny service or surveil. Mitigations: cryptographic node identity, web-of-trust admission.
• Endpoint compromise. Same as everywhere; harder when the endpoint is a small embedded device with limited security primitives.

Operational patterns

Disaster resilience kit

- 2× LoRa Meshtastic devices per household
- Solar charging
- Pre-shared channel keys distributed in person
- Offline maps and predefined fallback rendezvous
- Reticulum / LXMF for richer messaging if smartphones survive

Activist comms in shutdown

- Briar with Bluetooth + Tor
- Distributed channel keys via QR
- Pre-arranged identity rotation
- Briar Mailbox or trusted host as async store

Pseudonymous community network

- Reticulum nodes (Raspberry Pi + LoRa hat)
- LXMF accounts as identity
- Cross-community gateways via internet when available

Trade-offs

Strengths

• Survives infrastructure failure. No internet, no cloud, no DNS dependency.
• No external observers. A LoRa mesh is invisible to non-participants without DF gear.
• Cheap. $30 LoRa devices, free open-source firmware.

Limitations

• Bandwidth is brutal. A few kbit/s caps app design — text only, no media.
• Range is uneven. Topography, weather, foliage all affect link quality.
• Latency. Store-and-forward adds delay; not for synchronous chat.
• Discovery and bootstrapping. Out-of-band contact establishment is mandatory.
• DF risk. Active radios are physically locatable.

Primary Sources

• Meshtastic — meshtastic.org; github.com/meshtastic
• Reticulum / RNS — reticulum.network; github.com/markqvist/Reticulum
• LXMF — github.com/markqvist/LXMF
• Briar — briarproject.org
• Bridgefy security audit, Mesh-based messaging app cryptography, 2020.

LoRa mesh has two main firmware families: Meshtastic and its sibling MeshCore, which relays only through dedicated repeaters and learns routes. For a Bluetooth mesh on phones alone, with a Nostr fallback, see Bitchat.

Also in Secure Messaging