A novel chaos system with XOR operations and multi-bit PRBS is proposed to improve the sequence complexity and the security of the classic electro-optic intensity chaos system. Through the bifurcation diagram and permutation entropy analysis, the PE can be increased to 0.99. The key space is enlarged because additional DSP parameters and PRBS are introduced. The impacts of ADC/DAC characteristics and PRBS characteristics are analyzed in detail. The simulation results show that the time delay signature can be concealed with the appropriate DSP parameters.

To improve the output performance of the classical all-optical chaotic system and solve the security problems of its key exposure and small key space, a new chaotic system, to the best of our knowledge, based on logistic map post-processing is proposed. In terms of the general output performance of the system, the spectrum of the proposed system is flatter than the classical system. Through a bifurcation diagram and permutation entropy analysis, it is found that the output of the system is extremely complex. In terms of security, the simulation results show that, with a reasonable selection of system parameters, key hiding can be achieved under a large parameter range. Moreover, through the sensitivity analysis of logistic parameters, it can be seen that the introduction of logistic parameters can improve the key space of the system and further improve the security of the system.