论文标题
流/块密码，差异方程和代数攻击
Stream/block ciphers, difference equations and algebraic attacks
论文作者
论文摘要
在本文中，我们将一类流和密码块建模为有限字段上（普通）显式差异方程的系统。我们将此类称为“差异密码”，我们表明应用程序兴趣的密码，例如与组合仪，Trivium和Keeloq的LFSR系统属于该类。通过使用差异代数，即差异方程式的形式理论，我们可以正确定义和研究这些密码的重要特性，例如它们的可逆性和周期性。我们描述了从这些属性遵循的差异密码的一般隐次分析方法，可用于评估安全性。我们通过密码双臂和基洛克在实践中说明了这种代数攻击。
In this paper we model a class of stream and block ciphers as systems of (ordinary) explicit difference equations over a finite field. We call this class "difference ciphers" and we show that ciphers of application interest, as for example systems of LFSRs with a combiner, Trivium and Keeloq, belong to the class. By using Difference Algebra, that is, the formal theory of difference equations, we can properly define and study important properties of these ciphers, such as their invertibility and periodicity. We describe then general cryptanalytic methods for difference ciphers that follow from these properties and are useful to assess the security. We illustrate such algebraic attacks in practice by means of the ciphers Bivium and Keeloq.
