Algebraic Attacks on Summation Generators

We apply the algebraic attacks on stream ciphers with memories to the summation generator. For a summation generator that uses n LFSRs, an algebraic equation relating the key stream bits and LFSR output bits can be made to be of degree less than or equal to 2 log2 n , using log2 n + 1 consecutive key stream bits. This is much lower than the upper bound given by previous general results. We also show that the techniques of [5] can be applied to summation generators using 2k LFSRs to reduce the effective degree of the algebraic equation.

• Type: Conference
• Year: 2004
• Where: FSE
• Authors: Dong Hoon Lee 0002, Jaeheon Kim, Jin Hong, Jae Woo Han, Dukjae Moon
• Keywords: Algebraic Equation, Cryptography, FSE 2004, Key Stream Bits, Summation Generators