Document Type : Original Article

Authors

• Alireza Babaei
• Hamid Haj Seyyed Javadi
• Nader Jafari Rad

Shahed university

Abstract

Abstract:



Algebraic attack is an emergent decryption method. The main objective in this decryption is to form and solve a set of multivariate polynomial equations on finite fields. The present findings show that algebraic attacks have been significantly successful and effective on a specific type of stream ciphers system and linear-feedback shift register systems (LFSRs). One of the reasons for this is that linear functions are used for updating LFSRs, although the nonlinear types can also be approximated by an appropriate linear function, and this increases the necessity of paying attention to it. In the present article, an attempt is made to present the main idea of algebraic attacks on stream ciphers systems , and to explain these ideas by certain concrete examples. Particularly, a synchronousstream cipher system based on LFSRs, entitled the LILI stream ciphers, and algebraic attacks on them, will be discussed. In algebraic attacks, solving a set of multivariate polynomial equations is needed. In the present research, the extended linearization algorithm (XL) will be used to deal with an attained set of equations. Additionally, some of the accelerated extended algorithms (XL) for dealing with the set of equations algebraic resulted from the attacks on stream cipher systems, will be analyzed and their efficiency will be examined in the frame of certain examples.

Keywords

• Algebraic attack
• stream cipher
• extended Linearization algorithem