Flaw and amendment of a two-party authenticated key agreement protocol for post-quantum environments

Abstract

Recent advances in quantum computers challenge the security of key agreement protocol that are designed with the intractability assumptions of discrete logarithmic problem and integer factorization problem. Hence, motivated to develop the key agreement protocol that is secure in post-quantum era, recently Islam proposed a provably secure two-party authenticated key agreement (2PAKA) protocol. The protocol is based on the intractability assumption of the famous Ring Learning With Error (RLWE) problem. In this work, we show that Islam’s two-party key agreement is vulnerable to the modified version of the signal leakage attack (SLA) which is termed as improved-signal leakage attack (i-SLA) in this article. Using i-SLA, the attacker can successfully recover the long term private key of the honest user by instantiating utmost q number of key exchange sessions with the honest user using q number of malformed public keys. To overcome the attack, we provide a countermeasure without changing the original design of the protocol.