Substitution-permutation Network Cryptosystems Using Key-dependent S-boxes
نویسندگان
چکیده
Substitution-permutation networks (SPNs) are an important class of private key cryptosystems, having substitution boxes (s-boxes) as a critical internal component. Much of the research into s-boxes has focussed on determining those s-box properties which yield a cryptographically strong SPN. We investigate s-boxes which are generated in a pseudo-random fashion from a key. This approach has the advantage of decreasing the e ectiveness of certain attacks. In addition, combinatorial results give evidence that the resulting s-boxes will possess several desirable properties with high probability. We propose a key-dependent s-box generation method and an SPN which incorporates it. The proposed system successfully passes a range of standard statistical tests, as well as two new statistical tests which are designed to detect correlation between s-boxes. Some interesting theoretical results concerning these new tests are proven, and one of the tests is shown to be a generalisation of the existing test for s-box nonlinearity. i Acknowledgements I am grateful to my supervisor, Henk Meijer, for the fact that during the process of working on this thesis, he was a constant source of ideas, motivation, and encouragement. I am also thankful for my wonderful wife, Ronda, who brings joy to my life, and who gave me support through the (sometimes stressful) task of thesis creation. Most of all, I thank my Lord Jesus Christ, who truly came that we might have \life, and life more abundantly" (John 10:10). ii
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تاریخ انتشار 1997