Securing communication by chaos-based encryption

As a prerequisite for data encryption, a special spatiotemporal chaotic system, viz., a coupled map lattice (CML), is employed to design a multiple-output pseudo-random bit generator (PRBG). The CML can exhibit complicated chaotic phenomena both in space and in time, which is highly desirable for the PRBG to be applicable for encryption purposes as it guarantees random behaviour of the generated bit sequences. Cryptographic properties such as probability distribution, auto- and cross-correlation, and FIPS 140-2 tests of the PRBG are numerically investigated to determine certain parameter ranges where the PRBG has good cryptographic properties. Based on this PRBG, a stream cipher is presented. Its security is assessed by analysing diffusion and confusion, using various typical attacks. In addition, the encryption speed of the cipher is evaluated. As an example, an image is encrypted with the cipher. It is shown that the cipher has both low computation expense and high security and efficiency. © Springer-Verlag Berlin Heidelberg 2007.