A Hase-based SAKA Protocol Algorithm

It was pointed out that the simple authenticated key agreement (SAKA) protocol suffered three weaknesses. Several improved protocols, such as improved Lin protocol, E-SAKA protocol, then were proposed as claimed being free of these three weaknesses. After reviewing of these protocols, proofs are given that these protocols still suffer from the password guessing attack. Besides, the weakness that the attacker on the E-SAKA protocol can get the session key also is pointed out. By introducing hash function a new protocol based on improved Lin´s protocol is proposed, which is free of the three weaknesses and also can prevent man-in-the-middle attack as well as the password guessing attack.