We propose a new approach in cryptanalysis based on an evolution of the concept of \textit{Combinatorial Equivalence}. The aim is to rewrite a cryptosystem under a combinatorially equivalent form in order to make appear new properties that are more strongly discriminating the secret key used during encryption. We successfully applied this approach to the most secure stream ciphers category nowadays. We first define a concept cipher called Cipherbent6 that capture most of the difficulty of stream cipher cryptanalysis. We significantly outperformed all known cryptanalysis. We applied this approach to the Achterbahn cipher and we obtained again far better cryptanalysis results.

翻译：我们提出了一种基于组合等价性概念演化的密码分析新方法。该方法旨在将密码系统重写为组合等价形式，从而揭示能够更有效区分加密过程中所用密钥的新特性。我们成功地将该方法应用于当前最安全的流密码类别。首先，我们定义了一个名为Cipherbent6的概念密码，该密码涵盖了流密码密码分析中的主要难点。我们的方法显著超越了所有已知的密码分析技术。通过将该方法应用于Achterbahn密码，我们再次获得了远优于现有结果的密码分析成果。