Delivering messages with no internet, no servers, and no SIM

Description and use

Kabootar enables messaging without internet, servers, or SIM cards by using a Bluetooth/Wi‑Fi peer‑to‑peer mesh. It implements delay‑tolerant store‑and‑forward routing, end‑to‑end encryption, and delivery receipts.

Problem

Traditional messengers rely on continuous internet connectivity to a datacenter, making them unusable in environments without network access such as basements, stadiums, or remote areas.

Outcome

Kabootar delivers private messages without internet or servers by using a delay‑tolerant mesh network over Bluetooth/Wi‑Fi, achieving end‑to‑end delivery receipts and exactly‑once semantics at the edges.

Workflow

• 1. User opens Kabootar and sends a message to a nearby contact.
• 2. The message is broadcast to all devices in range using epidemic routing.
• 3. Each device de‑duplicates, stores, and forwards the message to new peers.
• 4. When the recipient’s device receives the message, it acknowledges it back through the same mesh.
• 5. The original sender receives the acknowledgment and marks the message as delivered.
• 6. Messages are persisted in SQLite to survive restarts and ensure exactly‑once delivery at the edges.

Evidence

Kabootar is a messenger with no backend at all. Your phone forms a peer‑to‑peer mesh with other phones nearby, and messages hop device to device over Bluetooth and Wi‑Fi until they reach the recipient.

Source

The routing strategy is epidemic routing: flooding. When you send a message, it spreads to everyone in range like a rumor.

Source

Direct chats and private groups are end‑to‑end encrypted with X25519, Ed25519, and AES‑GCM, with signed messages and a safety code to verify a contact.

Source