Cryptanalysis of Authenticated Key Agreement Protocols

Abstract

In 1999, Seo and Sweeney proposed a simple authenticated key agreement protocol that enables two parties, who share a password in advance, to authenticate each other and to share a common session key vie the Diffie-Hellman problem. Recently, Jseng showed that the Seo-Sweeney protocol is insecure against forgery and consequently proposed a modified protocol to repair it. Later, Ku and Wang addressed that Jseng’s protocol is also insecure against forgery and therefore an improved version was proposed. In this paper, we show that the three authenticated key agreement protocols, proposed by Seo et al., Tseng, and Ku et al. respectively, are insecure against off-line password guessing attacks if weak passwords are applied.