Weakness in simple authenticated key agreement protocol

Seo and Sweeney recently proposed a simple authenticated key agreement protocol using a password-based method [see ibid., vol. 35, no. 13, p. 1073, 1999]. They claimed that the established session key between two users is also verified. However, the author points out that verification of the session key cannot be achieved in their protocol. A slight improvement to their protocol is proposed to overcome this weakness