对分组密码的形式化函数分析及其应用

摘要

This paper introduces FFC(formal function cryptanalysis )of block cipher that expresses each bit in the ciphertext as pure formal functions in terms of the bits of the plaintext and master key by symbolic computation .As an application ,we give a meet in the middle attack on 13-round LBlock lightweight block cipher .The meet in the middle attack has a complexity of 276.2 13-round LBlock encryption using only 1 known plaintext ,which is better than the algebraic attack given by Nicolas Courtois etc .at FSE 2012 on 8-round LBlock ,with data complexity 6 known plaintexs .%本文给出了分组密码的新的分析方法：形式化函数分析，即通过符号计算将密文形式地表示为明文和密钥的函数．作为应用本文给出了13轮LBlock轻量级分组密码的一个中间相遇攻击．对13轮LBlock的中间相遇攻击的时间复杂度为276.2次13轮LBlock加密，数据复杂度为1个已知明文．优于Nicolas Courtois等人在FSE 2012上给出的8轮代数攻击，其数据复杂度为6个已知明文．