A new key authentication scheme for cryptosystems based on discrete logarithms

Key authentication is very important in private communication and data integrity. Recently, Peinado, Zhang and Kim showed that the LHL scheme is not secure, respectively. From public messages, anyone can derive private keys of users. Then they proposed their modifications to overcome this severe weakness, respectively. In this paper, we show that the Peinado's modification is still insecure, since anyone can still derive private keys of users by a guessing attack. Meanwhile, the modification of Zhang and Kim is based on three security prerequisites, which are expensive in an open environment. To overcome these shortcomings, we propose a new key authentication scheme for cryptosystems based on discrete logarithms.