On the (Non)improvement of an authenticated GKT protocol

Abstract

Harn and Lin proposed in 2010 a secret sharing-based group key transfer protocol. One year later, Nam et al. showed their construction is vulnerable to a replay attack and proposed a way to fix it. Recently, Yuan et al. analyzed the same protocol, proved that it is also vulnerable to a man-in-the middle attack and considered a countermeasure. First, we slightly modify Yuan et al.’s attack to make it simpler to implement and harder to be detected. Second, we show that the improved version of the protocol remains susceptible to a man-in-the-middle attack.