Controlled Parameter Modulations in Secure Digital Signal Transmissions
  We propose a simple method for secure digital signal transmission by making some modifications in the single-step parameter modulation technique proposed earlier into overcome certain inherent deficiencies. In the modified method, the parameter modulation is effectively regulated or controlled by the chaotic signal obtained from the transmitting chaotic system so that it has the maximum security. Then, the same idea is also extended to the multistep parameter modulation technique. It is found that both the methods are secure against ciphertext (return map) and plaintex attacks. We have illustrated these methods by means of the Lorenz system. 
P. Palaniyandi and M. Lakshmanan