Achterbahn

Abstract: We present several attacks against the Achterbahn stream cipher, which was proposed to the eSTREAM competition. We can break the reduced and the full version with complexity of 255 and 261 steps. Extensions of our attacks are also described to break modified versions of the Achterbahn stream cipher, which were proposed following the publication of preliminary cryptanalysis results. These attacks highlight some problems in the design principle of Achterbahn, i.e., combining the outputs of several nonlinear (but small) shift registers using a nonlinear (but rather sparse) output function.

Abstract: We present several attacks against the Achterbahn stream cipher, which was proposed to the eSTREAM competition We can break the reduced and the full version with complexity of 2 55 and 2 61 steps Extensions of our attacks are also described to break modified versions of the Achterbahn stream cipher, which were proposed following the publication of preliminary cryptanalysis results These attacks highlight some problems in the design principle of Achterbahn, ie, combining the outputs of several nonlinear (but small) shift registers using a nonlinear (but rather sparse) output function

Abstract: This paper presents two key-recovery attacks against Achterbahn- 128/80, the last version of one of the stream cipher proposals in the eSTREAM project The attack against the 80-bit variant, Achterbahn- 80, has complexity 261 The attack against Achterbahn-128 requires 28058 operations and 260 keystream bits These attacks are based on an improvement of the attack due to Hell and Johansson against Achterbahn version 2 They mainly rely on an algorithm that makes profit of the independence of the constituent registers

Abstract: We present several attacks against the Achterbahn stream cipher, which was proposed to the eSTREAM competition. We can break the reduced and the full version with complexity of 2 55 and 2 61 steps. Extensions of our attacks are also described to break modified versions of the Achterbahn stream cipher, which were proposed following the publication of preliminary cryptanalysis results. These attacks highlight some problems in the design principle of Achterbahn, i.e., combining the outputs of several nonlinear (but small) shift registers using a nonlinear (but rather sparse) output function.