Module pqxdh 

PQXDH key agreement protocol.

This module implements the PQXDH (Post-Quantum Extended Diffie-Hellman) key agreement, extracting the pure key agreement computation from ratchet initialization. The output includes derived keys ready for ratchet setup; the actual ratchet initialization is handled separately in the internal ratchet module.

Future direction

The KDF output shape (RootKey, ChainKey, [u8; 32]) is currently coupled to the Double Ratchet’s initialization requirements. Ideally, the handshake would output a single 32-byte secret and the ratchet layer would derive whatever it needs from that. This requires a protocol version bump and should be done alongside a future handshake protocol revision.

Structs

InitiatorParameters

Parameters for the initiator side of a PQXDH key agreement.

RecipientParameters

Parameters for the recipient side of a PQXDH key agreement.