Biham E., Dunkelman O., Keller N. (2002) Linear Cryptanalysis of Reduced Round Serpent. In: Matsui M. (eds) Fast Software Encryption. FSE 2001. Lecture Notes in Computer Science, vol 2355. Springer, Berlin, Heidelberg
Serpent is one of the 5 AES finalists. In this paper we present a 9-round linear approximation for Serpent with probability of 1/2+2-52. We use it to attack 10-round Serpent with all key lengths with data complexity of 2118 and running time of 289. A variant of this approximation is used in the first attack against an 11-round Serpent with 192-bit and 256-bit keys, which require the same amount of data and 2187 running time.