User authentication is an important security issue when user access resources from network. Recently, Xu et al.(XU C, JIA Z, WEN F, et al. Cryptanalysis and improvement of a dynamic ID based remote user authentication scheme using smart cards [J]. Journal of Computational Information Systems, 2013, 9(14): 5513-5520) proposed a dynamic ID based remote user authentication scheme using smart cards. Though the rigorous security analysis, it was found that Xu scheme could not resist man in-the-middle attack and session key disclosure attack, and could not provide perfect forward secrecy for session key. Additionally, it was also demonstrated that the scheme proposed by Choi et al. (CHOI Y, NAM J, LEE D, et al. Security enhanced anonymous multiserver authenticated key agreement scheme using smart cards and biometrics [J]. The Scientific World Journal, 2014, 2014: 281305)was vulnerable to smart card loss attack, server spoofing attack, and could not provide user anonymity. Therefore, these two schemes could not be suitable for practical applications. At last, an improved scheme was proposed based on biometrics and extended chaotic maps to overcome the lack of Xu scheme and CNL scheme.