SKINNY is a tweakable lightweight block cipher algorithm. In order to test its security, this paper performs optimal differential trail search analysis on all SKINNY-64 versions under single-key setting based on the MILP (Mixed Integer Linear Programming) algorithm. Firstly, SKINNY round function is abstracted equivalently by precise constraints, and the objective function is set as the minimum number of active S-box number to optimize SKINNY-64 MILP model. Experiments show the differential trail searched by this method is not necessarily optimal. In order to directly search for the optimal differential trail, the S-box differential probability coding information is added to the optimized SKINNY-64 MILP model, the S-box differential characteristic is reconstructed, and the objective function is set to the minimum value of the probability coding information, which improves the SKINNY-64 MILP model. The results of experimental show that the improved MILP model can directly search for the optimal differential trail, and the complexity is slightly increased, but the search efficiency is significantly improved. Under single-key setting, this method has obvious advantage in searching the optimal differential trails of SKINNY-64 with low round number.

中文翻译：

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SKINNY最优差分路径搜索的研究

SKINNY是一种可调整的轻量级分组密码算法。为了测试其安全性，本文基于MILP（混合整数线性规划）算法，在单键设置下对所有SKINNY-64版本执行了最佳差分路径搜索分析。首先，SKINNY舍入函数等效地通过精确约束抽象出来，并将目标函数设置为活动S盒数量的最小数量，以优化SKINNY-64 MILP模型。实验表明，用这种方法搜索的差分轨迹不一定是最优的。为了直接搜索最优差分轨迹，将S-box差分概率编码信息添加到优化的SKINNY-64 MILP模型中，重建S-box差分特性，并且将目标函数设置为概率编码信息的最小值，从而改进了SKINNY-64 MILP模型。实验结果表明，改进后的MILP模型可以直接搜索最优的差分路径，复杂度略有增加，但搜索效率明显提高。在单键设置下，该方法在寻找低轮数的SKINNY-64最优差分轨迹方面具有明显的优势。