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题目： Dimension of invariant subspace of a Stark-friendly symmetric cipher design

报告人：吴保峰 研究员（中科院信工所）

时间：2021年12月24日（周五） 上午9：00-11：00

地点：教二楼827

摘要：The HADES design strategy combines the classical SPN construction with the Partial SPN (PSPN) construction of symmetric ciphers. Starkad and Poseidon are two instantiations of HADES, both using Cauchy-type MDS matrices as diffusion layers. At Eurocrypt 2021, Keller and Rosemarin posed a successful attack on Starkad by showing that its PSPN part admitted a high dimensional invariant subspace. They also conjectured an improved bound for the dimension of this invariant subspace. In this talk, I will introduce Keller and Rosemarin's work, and explain how to prove their conjecture. This conjecture is essentially about the nullity of a matrix polynomial of a block matrix with Hadamard type blocks over commutative rings of characteristic 2. It turns out that the main argument leads to the proof is incredibly simple, as long as we have found the key point.

简介：吴保峰，本科毕业于山东大学数学学院，博士毕业于中科院数学与系统科学研究院，2013年博士毕业后进入中科院信息工程研究所从事博士后研究，现为信工所副研究员、硕士生导师。主要从事密码数学理论、密码算法设计与分析相关领域研究，在TIT、FFA、ISIT、FSE等国际期刊或会议发表论文30余篇，主持或参与国家自然科学基金面上项目、青年基金、专项基金以及军队密码合作基金等科研项目十余项。

联系人： 方江学、张俊

主办单位：首都师范大学77779193永利官网、首都师范大学交叉科学研究院