Cryptanalysis and Security Enhancement of Two Advanced Authentication Protocols

"In this paper, the authors consider two protocols for performing crypt-analysis and security enhancement. The first one by the researcher is a password-based authentication scheme which does not use smart cards. They note that this scheme is an improvement over the researcher scheme shown vulnerable to the o -line dictionary attack by the researcher. They perform a cryptanalysis on the researcher improved protocol and observe that it is prone to the clogging attack, a kind of Denial of Service (DoS) attack. They then suggest an improvement on the protocol to prevent the clogging attack."