Chaotic digital encoding: an approach to secure communication

A method for using chaos in the digital domain for secure communications is proposed. The method uses a nonlinear digital filter with finite precision (8 bits) in conjunction with its inverse filter to implement an encoder and a decoder, respectively. The nature of the encoder is such that it behaves in a quasi-chaotic fashion (since chaotic behavior requires infinite precision), both with zero and nonzero input sequences. The determination of its quasi-chaotic behavior is based on QC-properties defined in the paper, which are proposed as a test for finite state digital filters. At the very least, these properties suggest that the encoder possessing them will be of value in secure communications applications. Variations on the encoding scheme are suggested that allow the potential for a wide range of applications, ranging from cost-effective real-time systems to high security systems incorporating one or more “keys.” Simulation results as well as a mathematical analysis are used to promote an understanding of the performance of the nonlinear encoder/decoder