End-to-End Encrypted Messaging (X3DH)
Cryptographic specification of Madar Personal 1:1 and group conversations, media encryption, and safety numbers.
X3DH Key Agreement & Authenticated Payload Encryption
Every personal conversation establishes a shared session key using Extended Triple Diffie-Hellman (X3DH) over Curve25519 (X25519) with Ed25519 identity signatures and HKDF-SHA256 key derivation.
Messages and attachments are encrypted on the sender's device using AES-256-GCM or XChaCha20-Poly1305 before transmission. The server stores and relays only opaque ciphertext envelopes.