Abstract:

With the deepening of the research on block cipher application, the design of “dynamic variable” block cipher can effectively improve the application flexibility and deployment security of block cipher algorithm. CLEFIA algorithm follows the idea of “dynamic variable”, some scholars have improved the linear transformation layer of CLEFIA algorithm, so that the diffusion layer in the 6t(t≥1) round can be arbitrarily selected from the {0,1}⁴ multiple linear bijection transforms. In order to analyze and evaluate the security performance of CLEFIA dynamic cipher structure, this paper mainly adopted the theory of zero-correlation linear analysis, and used the miss-in-the-middle technique and matrix representation method to analyze the zero-correlation linear discriminator of CLEFIA dynamic cipher structure. The results show that under the condition that the wheel function is bijective, no matter what the control parameters μ_i∈F₂,(0≤i≤4) of the dynamic linear layer of CLEFIA dynamic cipher structure are, there are always 8 rounds of zero-correlation linear discriminators. When controlling parameters μ₀=0, there are 9 rounds of zero-correlation linear discriminators.

Key words: block cipher, CLEFIA dynamic cipher structure, zero correlation linear analysis, miss-in-the-middle technique, matrix representation