Digital chaotic sequence generator based on coupled chaotic systems

Chaotic systems perform well as a new rich source ofcryptography and pseudo-random coding. Unfortunately their digitaldynamical properties would degrade due to the finite computingprecision. Proposed in this paper is a modified digital chaoticsequence generator based on chaotic logistic systems with a couplingstructure where one chaotic subsystem generates perturbation signalsto disturb the control parameter of the other one. The numericalsimulations show that the length of chaotic orbits, the outputdistribution of chaotic system, and the security of chaoticsequences have been greatly improved. Moreover the chaotic sequenceperiod can be extended at least by one order of magnitude longerthan that of the uncoupled logistic system and the difficulty indecrypting increases 2¹²⁸*2¹²⁸ times indicating that thedynamical degradation of digital chaos is effectively improved. Afield programmable gate array (FPGA) implementation of an algorithmis given and the corresponding experiment shows that the outputspeed of the generated chaotic sequences can reach 571.4~Mbpsindicating that the designed generator can be applied to thereal-time video image encryption.