Analysis of LFSR Based Snow Family against Guess and Determine Attack

Stream Cipher is a cryptographic primitive that is used to make sure privacy on a communication channel. SNOW family is a typical example of word oriented stream ciphers based on Linear Feedback Shift Register (LFSR). In this paper two versions of SNOW family have been analyzed against Guess and Determine (GD) Attack. Original SNOW 2.0 is an improved version of SNOW 1.0 claimed to be more secure and efficient in performance. Vulnerabilities in SNOW 2.0 give rise to another version of SNOW 2.0 called Modified SNOW 2.0. Both versions have claim that their model is secure against Guess and Determine attack. The purpose of this paper is to verify their claimed and to determine that which version has more resistance against Guess and Determine attack. Both algorithms are evaluated experimentally in two phases. Analysis and experimental results indicate that, for small number of key streams Modified SNOW 2.0 shows more resistance against GD attack. But when the number of key streams generated becomes larger Original SNOW 2.0 becomes more secure.