Cryptanalysis of Achterbahn

We present several attacks against Achterbahn, one of the new stream ciphers proposed to the eSTREAM competition. Our best attack breaks the reduced version of the cipher with complexity of 256 steps and the full version with complexity of 273 steps. It highlights some problems in the design principle of Achterbahn, i.e. combining the outputs of several non-linear (but small) shift registers using a non-linear (but rather sparse) output function.

• Type: Conference
• Year: 2006
• Where: FSE
• Authors: Thomas Johansson, Willi Meier, Frédéric Muller
• Keywords: Cryptology, ESTREAM Competition, FSE 2006, Reduced Version, Shift Registers