A New Analysis Method for Nonlinear Component of Stream Ciphers
Yongbin Zhao · Journal of Information and Computational Science · 2013
A popular construction of stream ciphers is to combine several LFSRs and nonlinear components, such as a Nonlinear Feedback Shift Register (NFSR) and a Boolean function. In this paper, we present a new analysis method for stream ciphers based on the Walsh spectrum. Besides the security properties, balancedness, nonlinearity and correlation immunity of nonlinear component, our works are focused on the key points of the values of Walsh spectrum, which influence these security indicators. By this method, the weakness of nonlinear component can be found more easily and clearly. Finally, we use this method to analyze the Grain v1 and point out its’ security weakness.