Estimating short-time period to break different types of chaotic   modulation based secure communications
  In recent years, chaotic attractors have been extensively used in the design of secure communication systems. One of the preferred ways of transmitting the information signal is binary chaotic modulation, in which a binary message modulates a parameter of the chaotic generator. This paper presents a method of attack based on estimating the short-time period of the ciphertext generated from the modulated chaotic attractor. By calculating and then filtering the short-time period of the transmitted signal it is possible to obtain the binary information signal with great accuracy without any knowledge of the parameters of the underlying chaotic system. This method is successfully applied to various secure communication systems proposed in the literature based on different chaotic attractors. 
Gonzalo Alvarez and Shujun Li