Cryptanalysis and improvement of an extended chaotic maps-based key agreement protocol

Very recently, Lee et al. (C. Lee, C. Chen, C. Wu, S. Huang, An extended chaotic maps-based key agreement protocol with user anonymity, Nonlinear Dynamics, doi: 10.1007/s11071-011-0247-4 ) proposed a chaotic maps-based key agreement protocol with user anonymity and claimed their protocol could resist various attacks. In this paper, we will point out that Lee et al.’s protocol suffers from three weaknesses: (1) inability of resisting the privileged insider attack; (2) inability of resisting the denial-of-service attack; and (3) inability of providing anonymity. To overcome the weaknesses, we also proposed an improved protocol. The analysis shows our protocol is more suitable for practical applications.