Comments on Modified User Friendly Remote Authentication Scheme with Smart Cards

摘要

Recently, Wu-Chieu proposed an improvement to their original scheme, in order to make the scheme withstand impersonation attacks. However, the improved scheme is susceptible to an off-line password guessing attack and is inefficiently designed. Accordingly, the current letter demonstrates the vulnerability of Wu-Chieu's modified scheme to an offline password guessing attack and evaluates the efficiency of their schemes and related schemes.