A proposal for a new block encryption standard
EUROCRYPT '90 Proceedings of the workshop on the theory and application of cryptographic techniques on Advances in cryptology
Differential cryptanalysis of the data encryption standard
Differential cryptanalysis of the data encryption standard
The Data Encryption Standard (DES) and its strength against attacks
IBM Journal of Research and Development
Linear cryptanalysis method for DES cipher
EUROCRYPT '93 Workshop on the theory and application of cryptographic techniques on Advances in cryptology
A fast algorithm for the bound consistency of alldiff constraints
AAAI '98/IAAI '98 Proceedings of the fifteenth national/tenth conference on Artificial intelligence/Innovative applications of artificial intelligence
Contradicting Conventional Wisdom in Constraint Satisfaction
PPCP '94 Proceedings of the Second International Workshop on Principles and Practice of Constraint Programming
CRYPTO '89 Proceedings of the 9th Annual International Cryptology Conference on Advances in Cryptology
Refining the basic constraint propagation algorithm
IJCAI'01 Proceedings of the 17th international joint conference on Artificial intelligence - Volume 1
Construction of high degree resilient S-boxes with improved nonlinearity
Information Processing Letters
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We use the Constraint Satisfaction Problem (CSP) framework to model and solve the problem of designing substitution functions for substitutionpermutation (SP) networks as proposed by Shannon for the architecture of ciphers. Many ciphers are designed using the SP pattern, and differ mainly by two parametrized functions: substitution and permutation. The most difficult of the two is the substitution function, which has to be nonlinear (a requirement that was difficult to define and quantify). Over time, researchers such as Nyberg, Pieprzyk and Matsui have proposed various metrics of nonlinearity that make the function robust to modern attacks. Before us, people have attempted various ways to design functions that respect these metrics. In the past people hand-picked substitution tables (S-boxes) by trying various values. Recently they use difficult to analyze constructs (such as Bent functions, spectral inversion, inverses in Galois fields) whose outputs are tested for nonlinearity. While efficient, such techniques are neither exhaustive (optimal), nor did they manage to generate better substitutions than the ones hand-picked in the past. We show that Matsui's nonlinearity requirement can be naturally modelled using CSPs. Based on a combination of existing CSP techniques and some new filtering operators that we designed specially for the new types of constraints, we manage to obtain better S-boxes than any previously published ones. The simplicity of the CSP framework and availability of general CSP solvers like ours, makes it easy for more people to design their own ciphers with easy to understand security parameters. Here we report on this new application of CSPs.