Multi-User CDH Problems and the Concrete Security of NAXOS and HMQV

ePrint Report: Multi-User CDH Problems and the Concrete Security of NAXOS and HMQV

Eike Kiltz, Jiaxin Pan, Doreen Riepel, Magnus Ringerud

We introduce CorrGapCDH, the Gap Computational Diffie-Hellman problem in the multi-user setting with Corruptions. In the random oracle model, our assumption tightly implies the security of the authenticated key exchange protocols NAXOS in the eCK model and (a simplified version of) X3DH without ephemeral key reveal. We prove hardness of CorrGapCDH in the generic group model, with optimal bounds …

computational diffie eprint report exchange gap hellman key oracle pan problem problems protocols prove random report security version