Traceable Bit Streams in SNOW 2.0 using Guess-and-Determine Attack
Syed IrfanUllah, Tarannum Naz, Malik Sikandar, Hayat Khiyal · 2010
2 Abstract: Word Oriented Stream Ciphers is an efficient class of stream ciphers in which basic operation is performed on a block of bits called word. Word Oriented Stream Ciphers become very popular because they generate block of several bits instead of one bit per clock. SNOW family is a typical example of word oriented stream ciphers based on Linear Feedback Shift Register (LFSR). In this paper we discuss SNOW family 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. The model claims that it is secure against Guess-and-Determine attack but our analysis show that it contains a series of patterns of bits that is traceable. We analyze the key stream generated by the SNOW 2.0 key stream generator against Guess-and-Determine attack to find out the probability and variance of the traceable bit patterns in key. Our analysis shows that logic based stream ciphers have these traceable patterns those cannot be avoided using logic based approaches. The algorithm is evaluated in three phases. The first phase discusses theoretical background of algorithm, the second phase discusses methodology adopted for Guess-and-Determine attack and the third phase discusses statistical analysis of attack.