Improving security of a chaotic encryption approach

E. Alvarez et al. presented a new chaotic encryption approach recently. But soon G. Alvarez et al. broke it with four cryptanalytic methods and found some other weaknesses. In this Letter we point out why the original scheme is so vulnerable to the proposed four attacks. The chief reasons are two es sential defects existing in the original scheme. Based on such a fact, we p resent an improved encryption scheme to obtain higher security. The cryptog raphic properties of the improved scheme are studied theoretically and expe rimentally in detail. (C) 2001 Elsevier Science B.V. All rights reserved.