Cryptanalysis of grain
Grain [11] is a lightweight stream cipher proposed by M. Hell, T. Johansson, and W. Meier to the eSTREAM call for stream cipher proposals of the European project ECRYPT [5]. Its 160-bit internal state is divided into a LFSR and an NFSR,of length 80 bits each. A filtering boolean function is used to derive each keystream bit from the internal state. By combining linear approximations of the feedbac