Cryptanalysis of Improved One-round Lin-Li´s Tripartite Key Agreement Protocol

A tripartite authenticated key agreement protocol is designed for three entities to communicate securely over an open network particularly with a shared key. Recently, we have improved a one-round tripartite authenticated key agreement protocol proposed by Lin-Li due to its vulnerability to the forging attack in our previous report. However, we have later discovered that both the original Lin-Li´s scheme and our previous enhanced protocol are vulnerable to the insider replay attack. Moreover, we have also realized that both protocols have falsely claimed the forward secrecy attribute. In this paper, we will revise our improvements and again secure this protocol against these cryptanalytic attacks while recovering the precious perfect forward secrecy property.