Analysis and Improvement of an Efficient and Secure Key Agreement Protocol

Improperly chosen parameters will lead to short period distribution of sequences generated by Chebyshev maps over finite fields ZN. However, in a key agreement protocol proposed by Yoon, et al. there is no consideration given to the avoidance of short period distribution. Based on the theory of period distribution the protocol is broken with other information gained from the key establishment process. In this paper, the protocol of Yoon, et al. is broken and improved by getting rid of unnecessary information and encrypting sensitive information, which makes the protocol more secure.