八轮MISTY1算法的相关密钥扩大飞来去器攻击

密钥扩展算法对分组密码的安全至关重要,目前各种攻击方法越来越关注密钥带来的影响.通过分析非线性函数FI和密钥扩展算法,并观察轮子密钥的排列方式,寻找到MISTY1算法一个包含290个弱密钥的、可应用于相关密钥扩大飞来去器攻击的弱密钥类.在弱密钥类的基础上,寻找到两条相互独立的相关密钥差分路径,从而构造了一个七轮MISTY1算法的相关密钥扩大飞来去器区分器,进而实现了对八轮MISTY1算法(不带最后FL层)的相关密钥扩大飞来去器攻击.攻击需要263个选择明文,攻击的计算复杂度是270.该攻击是第一个对不带最后FL层MISTY1算法的八轮攻击,且与同类攻击方法相比,攻击算法放宽了所需要的相关密钥的限制条件.

Related-key amplified boomerang attack on 8-round MISTY1

The key schedule algorithm plays a crucial role in the block cipher,thus many attacks pay more attention to it at present.Through analyzing the non-linear function FI and the key schedule algorithm of MISTY1,and observing the distribution of subkeys as well,a weak-key class of MISTY1 was found,which encompasses 290 weak keys that are vulnerable to related-key amplified boomerang attack.Based on the weak-key class,two related-key differential characteristics were found.Then,the research presented a 7-round related-key amplified boomerang distinguisher of MISTY1,which can accomplish an attack on the 8-round MISTY1 without the last FL lay.The attack requires 263 chosen plaintexts,and the time complexity of the attack is 270.The attack is the first attack on MISTY1 without the last FL lay.Besides,compared with the similar attacks,the limit of the related-key of our attack is released.