Robin算法改进的6轮不可能差分攻击

Robin算法是Grosso等人在2014年提出的一个分组密码算法。研究该算法抵抗不可能差分攻击的能力。利用中间相错技术构造一条新的4轮不可能差分区分器，该区分器在密钥恢复阶段涉及到的轮密钥之间存在线性关系，在构造的区分器首尾各加一轮，对6轮Robin算法进行不可能差分攻击。攻击的数据复杂度为2118.8个选择明文，时间复杂度为293.97次6轮算法加密。与已有最好结果相比，在攻击轮数相同的情况下，通过挖掘轮密钥的信息，减少轮密钥的猜测量，进而降低攻击所需的时间复杂度，该攻击的时间复杂度约为原来的2?8。

Revised Impossible Differential Attack on Reduced 6-Round Robin

Robin is a block cipher which was designed by Grosso et al in 2014. Its ability against impossible differential attack is studied. Firstly, a new 4-round impossible differential is constructed, and there is linear relationship for the round keys which are involved in the key recovered phase for the distinguisher. Then, reduced 6-round Robin is attacked by adding one round cipher at the beginning and the end to the constructed distinguisher. The data complexity of this attack is 2118.8 chosen plaintexts, and the time complexity of this attack is 293.97 6-round encryptions. Compared with the known best result, by exploiting the information of the round key, the number of the guessed round key can be reduced, and the time complexity of this attack is further lower. More precisely, the time complexity is about reduced by a factor of 2?8 under the same round number of the attack.