Cryptography you can
verify.

The Post-Quantum Extended Diffie-Hellman protocol combines classical X25519 elliptic curve key exchange with ML-KEM-768 (Kyber) post-quantum key encapsulation. This hybrid approach ensures that even if one scheme is broken, the other maintains security. Key agreement produces a shared secret that is computationally infeasible to derive for any adversary — classical or quantum.

After the initial key exchange, every message uses the Double Ratchet protocol to derive unique encryption keys. The symmetric ratchet advances with each message, while the Diffie-Hellman ratchet rotates with each round-trip. This provides forward secrecy (past messages can't be decrypted if keys are compromised) and break-in recovery (future messages become secure again after a compromise).

Identity verification uses a hybrid signature scheme combining Ed25519 (classical) with ML-DSA-65 (Dilithium, post-quantum). Both signatures must verify for authentication to succeed. This ensures that device identity and message authenticity remain unforgeable even against quantum adversaries.

Standard encrypted messaging protects message content but exposes metadata — who is talking to whom. Veils uses sealed sender envelopes: the sender's identity is encrypted inside the message payload using the Noise Protocol (NK pattern). The server relays messages without knowing the sender, providing true metadata protection.

When internet connectivity is unavailable, Veils can send encrypted messages over Bluetooth Low Energy. The BLE protocol uses the same cryptographic primitives as the online protocol — messages are encrypted with AES-256-GCM using keys derived from the Double Ratchet. Proximity-based key verification adds an additional layer of trust.