Methods and instruments for designing S-boxes

The design of S-boxes with minimal mutual information between input and output subvectors (considered as random variables) is investigated. First, the conditional entropy of the value of a boolean function conditioned on its random arguments is expressed as a function of the Walsh transform of the function. The entropy profile of a function is then defined; it allows the comparison of functions with regard to their (conditional) entropies. An algorithm to construct functions with good entropy profiles is then presented. It consists of a stepwise improvement of randomly chosen functions and uses the relation between the Walsh transform and the (conditional) entropies of a function. The statistical independency of boolean functions is investigated in the final section.     

广州广船国际股份有限公司计量中心空调改造

本文主要介绍广州广船国际股份有限公司计量室的恒温恒湿空调工程的改造。