⸻
📄 BitPhone Mesh Protocol (BPM)
Full-Duplex Audio Calls Over Bitcoin-Incentivized Mesh Relays
⸻
Abstract
BitPhone is a decentralized communication protocol that enables voice calls over mesh networks using incentivized relays powered by Bitcoin micropayments. Leveraging Bluetooth, Wi-Fi Direct, LoRa, and eventually Starlink uplinks, BitPhone allows permissionless, infrastructure-free calling — even in offline or adversarial environments.
⸻
Core Innovations
1. Audio-over-Mesh: Full-duplex (or half-duplex fallback) voice transmission over dynamic mesh networks using open codecs and transport abstraction layers.
2. Relay Incentivization: Use of Lightning Network (BOLT11 or LNURL) or eCash (e.g., Cashu) to pay relays per packet hop.
3. Voice Sessions with Noise Protocol: Voice calls encrypted end-to-end using Noise Protocol XX with persistent fingerprints, rotating IDs.
4. Store-Call-Forward: Similar to SMS store-and-forward, enables voice messages to be relayed when offline users return to mesh proximity.
5. Mesh-Dialing Layer: No phone numbers. Users dial by public key fingerprint or Nostr pubkey alias, optionally via ENS-like name resolution.
⸻
Protocol Stack Overview
+-------------------------------+
| Application Layer (Voice) |
+-------------------------------+
| Noise Protocol Encryption |
+-------------------------------+
| RTP/Opus Voice Encoding |
+-------------------------------+
| Mesh Transport Abstraction |
| (BLE, Wi-Fi Direct, LoRa) |
+-------------------------------+
| Incentivized Routing Layer |
| (Bitcoin Lightning / eCash) |
+-------------------------------+
⸻
How It Works
🎤 1. Audio Encoding
• Uses Opus codec with 8–16 kHz sample rate (adjustable).
• Voice is chunked into frames (e.g., 20ms segments), encrypted, and streamed over mesh.
🔐 2. Encryption
• Voice frames are encrypted using Noise Protocol XX.
• Supports key rotation and ephemeral relays without compromising end-to-end security.
🪙 3. Incentivized Relaying
• Every relayed hop includes optional Bitcoin Lightning reward.
• Users specify max sats per minute or sats per hop.
• Nodes with high uptime or bandwidth earn relay reputation and micropayments.
🧭 4. Routing & Discovery
• Nodes gossip peer availability.
• Pubkey/address book synced using Nostr relays or local P2P.
• DHT-inspired ephemeral routing for mobile mesh topologies.
⸻
Key Features
📱 Infrastructure-Free Voice
• Calls work in remote, offline, or censored environments.
• Supports BLE (short-range), Wi-Fi Direct (medium-range), and LoRa (long-range).
🔐 Privacy & Anonymity
• No phone numbers, email, or identity binding.
• Peer IDs rotate every X minutes. Fingerprints used for long-term trust.
• Optional voice obfuscation or voiceprint cloaking.
⚡ Micropayment Integration
• Users fund temporary wallets or ecash tokens for relay usage.
• Supports:
• Lightning invoices (BOLT11 or LNURL-pay)
• eCash/Cashu tokens
• Future integration with Fedimint custodians
📞 Call Modes
• Live Mode: Active, full-duplex audio stream.
• Burst Mode: Short audio bursts (PTT-style).
• Offline Voicemail: Voice memo sent as audio file over store-and-forward.
⸻
Use Cases
Scenario Description
🛰 Remote Calling Make calls in rural or disconnected zones using relay mesh
🚫 Blackout Mode Communicate during government shutdowns or natural disasters
🛡 ProtestOps Anonymous encrypted calls during high-risk events
🧭 Off-grid Coordination For activists, NGOs, survivalists, and homesteaders
🐝 Urban Mesh Swarms Dense city areas become self-healing communication zones
⸻
Economic Model
⚙ Relay Revenue Flow
[ Caller ] —(Packet + Sats)→ [ Relay A ] —→ [ Relay B ] —→ [ Receiver ]
↘ 5 sats ↙ 5 sats
(Invoice per hop via LNURL or ecash burn)
• Optional: Relays only accept packets with valid Lightning payment proofs.
• Micropayment policies customizable per relay node (fee per KB, per session, etc.).
⸻
Integration Points
• 🔄 BitChat Integration: Share pubkeys, presence, and call initiation via BitChat’s P2P channel.
• 📡 Meshtastic Layer: Use radios as low-bandwidth relays for emergency voice transmission.
• 🌐 Nostr Names: Optional DNS-like pubkey mapping for human-friendly dialing.
⸻
Security Model
• E2E Encryption: Calls are encrypted using Noise XX regardless of route path.
• Relay Obfuscation: Relays see packets but can’t decrypt contents or origin/final dest.
• DoS Protection: Relay whitelists, payment limits, and session caching to prevent abuse.
• Replay & Tampering Resistant: Packet signature chains and rolling nonces.
⸻
Challenges
Issue Mitigation
🔋 Battery Drain Codec bitrate throttling, adaptive QoS
🗣 Voice Latency Use Wi-Fi Direct/LoRa in tandem for balanced routes
🎭 Identity Abuse Fingerprint & social reputation verification
🔁 Relay Saturation Economic limits and back-pressure routing
⸻
Consider
BitPhone Mesh Protocol enables a new class of resilient communication — where voice isn’t owned by telcos or surveillance regimes, but flows peer-to-peer and is supported by value-for-value relaying. It’s a Bitcoin-native liberation tool, designed to work in the worst conditions imaginable — and still be private, clear, and borderless.
⸻
🔧 Next Steps
1. Prototype audio-over-BLE mesh using Opus + Noise + BitChat transport.
2. Develop relay incentive plugin for routing payments per hop.
3. Run simulations in disaster/testnet environments.
4. Integrate with Nostr + LN wallets (e.g., Alby, Phoenix).
5. Draft testnet spec with sample relay node and payment stub.
⸻