Results from a Search for the Best Linear Approximation of a Block Cipher.
Kashif Ali, Howard M. Heys · 2008
Abstract: In this paper, we investigate the application of an algorithm to find the best linear approximation of a basic Substitution-Permutation Network block cipher. The results imply that, while it is well known that the S-box used for the Advanced Encryption Standard has good nonlinear properties, it is straightforward to randomly select other S-boxes which are able to provide a similar level of security, as indicated by the exact bias of the best linear approximation found by the algorithm, rather than a simple upper bound on the maximum bias.