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5. Design methods for semi-bent functionsEnes Pašalić, Sugata Gangopadhyay, WeiGuo Zhang, Samed Bajrić, 2019, original scientific article Abstract: Semi-bent functions play an important role in the construction of orthogonal variable spreading factor codes used in code-division multiple-access (CDMA) systems as well as in certain cryptographic applications. In this article we provide several infinite classes of semi-bent functions, where each class is characterized by either a different decomposition of such a function with respect to the Walsh spectra of its subfunctions, or by the method used for its derivation. In particular, we also give the exact number of possibilities of decomposing bent functions, in a subclass of the Maiorana-McFarland class.
Keywords: cryptography, Boolean functions, bent functions, semi-bent functions, derivatives
Published in RUP: 19.12.2018; Views: 4581; Downloads: 174
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10. On cryptographically significant mappings over GF(2 [sup] n)Enes Pašalić, 2008, published scientific conference contribution Abstract: In this paper we investigate the algebraic properties of important cryptographic primitives called substitution boxes (S-boxes). An S-box is a mapping that takes ▫$n$▫ binary inputs whose image is a binary ▫$m$▫-tuple; therefore it is represented as ▫$F:\text{GF}(2)^n \rightarrow \text{GF}(2)^m$▫. One of the most important cryptographic applications is the case ▫$n = m$▫, thus the S-box may be viewed as a function over ▫$\text{GF}(2^n)$▫. We show that certain classes of functions over ▫$\text{GF}(2^n)$▫ do not possess a cryptographic property known as APN (AlmostPerfect Nonlinear) permutations. On the other hand, when ▫$n$▫ is odd, an infinite class of APN permutations may be derived in a recursive manner, that is starting with a specific APN permutation on ▫$\text{GF}(2^k), k$▫ odd, APN permutations are derived over ▫$\text{GF}(2^{k+2i})$▫ for any ▫$i \geq 1$▫. Some theoretical results related to permutation polynomials and algebraic properties of the functions in the ring ▫$\text{GF}(q)[x,y]$▫ are also presented. For sparse polynomials over the field ▫$\text{GF}(2^n)$▫, an efficient algorithm for finding low degree I/O equations is proposed.
Keywords: cryptoanalysis, cryptography, permutation polynomials, power mappings, APN functions, S-box, CCZ-equivalence, algebraic properties
Published in RUP: 15.10.2013; Views: 4232; Downloads: 75
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