Tightly-Secure Authenticated Key Exchange without NAXOS' approach based on Decision Linear Problem

Design secure Authenticated Key Exchange (AKE) protocol without NAXOS approach is remaining as an open problem. NAXOS approach [4] is used to hide the secret ephemeral key from an adversary even if the adversary in somehow may obtain the ephemeral secret key. Using NAXOS approach will cause two main drawbacks, (i) leaking of the static secret key which will be used in computing the exponent of the ephemeral public key. (ii) maximize of using random oracle when applying to the exponent of the ephemeral public key and session key derivation. In this paper, we present another AKE-secure without NAXOS approach based on decision linear assumption in the random oracle model. We fasten our security using games sequences tool which gives tight security for our protocol.