Guess and Determine Attack on SNOW 2.0

The guess-and-determine attack is a widely used cryptanalysis method in stream ciphers. This paper explores the application of the guess-and-determine attack on the SNOW 2.0 stream cipher algorithm. SNOW 2.0 is an improved version of its predecessor, SNOW 1.0, offering enhanced security and performance. However, through guess-and-determine attacks, vulnerabilities in SNOW 1.0 are revealed. The attacker uses relationships between internal variables of the cipher to make educated guesses about the keystream's state variables, such as those in the FSM and LFSR. This study focuses to apply this attack on SNOW 2.0, using the same assumptions and linear relationships approaches between variables. The results success to reduce the attack complexity compared to brute force attack with complexity of 2512. The complexity of this attack is estimated at 2<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">256</sup>, which, while still computationally expensive, is more efficient than a brute force approach. This research highlights potential weaknesses in SNOW 2.0 that can be exploited under specific conditions, offering insights into its cryptographic robustness.