GhostWire Mesh Network Uses XChaCha20-Poly1305 for Portable, Forward-Secure Encryption

GhostWire, a mesh networking project, uses XChaCha20-Poly1305 as its primary encryption cipher instead of the more common AES-256-GCM, citing the need for consistent performance across low-end hardware like ESP32 and Raspberry Pi devices that lack hardware AES acceleration. The cipher's 192-bit nonce prevents exhaustion even when millions of messages are encrypted under the same key, a real concern in high-traffic mesh environments. To protect against node compromise, GhostWire implements a Double Ratchet mechanism inspired by Signal, deriving a fresh session key per message and deleting previous keys so past communications remain secure. Key exchange combines classical X25519 ECDH with post-quantum ML-KEM-768, feeding both shared secrets into HKDF so that an attacker must break both algorithms to recover the encryption key. The approach is designed to address mesh-specific threats including out-of-order message delivery, frequent key rotation, and the possibility of individual nodes being compromised.