Key-sensitivity improvement of block cipher systems based on nonlinear feedback shift registers

We proposed a block cipher system based on the discretized Bernoulli map that can be implemented by nonlinear feedback shift registers (NFSRs). We examined basic characteristics of the proposed 64-bit block cipher system consisting of eight 8-stage NFSRs, where the eight NFSRs are parallel-processed. In this paper, we propose several new methods of secret key setting of the block cipher system for improvement of the key sensitivity. We evaluate the key sensitivity of the new key settings and compare it with the conventional method.