PQDH (Post-Quantum Diffie-Hellman) is a quantum-safe replacement for Diffie-Hellman based on SIDH – an elliptic curve isogeny-based scheme. SIDH, SIKE, and PQDH can be viewed as one family or variants of each other. SIDH was the original elliptic curve isogeny-based scheme, SIKE is the KEM (Key Encapsulation Mechanism)version of it, submitted to NIST Post-Quantum Cryptography Standardization process, and PQDH is InfoSec Global’s own invention.One property in common for all post-quantum key agreement candidates is the fact that the initiator and the responder perform different actions. However, for Diffie-Hellman-like schemes that are currently used, we do not need to distinguish between the actions of the two parties. PQDH solves exactly that issue and is currently the most plausible scheme to be a drop-in replacement for Diffie-Hellman-like schemes.
The paper for PQDH was accepted to NIST’s SecondPQC Standardization Conference.The paper goes further and proposed countermeasures against side-channel fault attacks and a PQDH-based PAKE (Password Authenticated Key Exchange).