Abstract:
During the last decade, a variety of chaos-based cryptosystems has been introduced to
protect the content of the transmitted images. In this paper, we propose a new fast,
simple, and robust chaos-based cryptosystem structure and we analyze its performances.
The cryptosystem uses a diffusion layer followed by a bit-permutation layer, instead of
byte-permutation, to shuffle the positions of the image pixels. Moreover, the permutation
layer is achieved by a new proposed formulation of the 2D cat map that allows an efficient
implementation, measured by the time complexity, in terms of arithmetic and logic
operations, and also, in terms of clock cycles, of the key-dependent permutation process
in comparison with the standard one. Hence, it provides a very fast diffusion process to
spread the influence of a single bit over the others. The new cryptosystem includes a
robust and uniform chaotic pseudo-random generator (a very simplified version of a
generator published in our patent) to change the control parameters in each round of the
encryption/decryption processes. The generator is highly nonlinear and produces robust
sequences of discrete values having very long orbits. The proposed cryptosystem is
defined on finite numbers, and its speed is faster than many chaos-based cryptosystems,
while having a very high security level. The security analysis and the obtained simulation
results show that the proposed cryptosystem is resistant to various types of attacks and it
is efficient for hardware and software implementation.
