We study the Lai–Massey construction defined over bit strings w.r.t. the notion of sequential indifferentiability, which was introduced by Mandal et al. (in: Cramer (ed) TCC 2012, LNCS, Springer, Heidelberg, vol 7194, pp 285–302, 2012) and formalized known-key security of blockcipher structures. We first exhibit a sequential distinguisher against 5-round Lai–Massey structure when the underlying orthomorphism is linear. This enhances a 2011 result of Aumasson. As our main result, we (for the first time) prove sequential indifferentiability for 6-round Lai–Massey constructions (on bit strings) using six independent random round functions.

我们研究了在位串上定义的 Lai-Massey 构造，以及由 Mandal 等人引入的顺序不可微性概念。 （参见：Cramer (ed) TCC 2012，LNCS，Springer，Heidelberg，第 7194 卷，第 285-302 页，2012 年）以及块密码结构的形式化已知密钥安全性。当底层的同态是线性时，我们首先展示针对 5 轮 Lai-Massey 结构的顺序区分器。这增强了 Aumasson 2011 年的业绩。作为我们的主要结果，我们（第一次）使用六个独立的随机轮函数证明了 6 轮 Lai-Massey 结构（在位串上）的顺序不可微性。