ElimLin Algorithm Revisited
| Autor: | Petr Sušil, Serge Vaudenay, Nicolas T. Courtois, Pouyan Sepehrdad |
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| Rok vydání: | 2012 |
| Předmět: |
Discrete mathematics
Polynomial Sequence Monomial algebraic cryptanalysis Linear space 010102 general mathematics systems of sparse polynomial equations of low degree 02 engineering and technology System of linear equations 01 natural sciences Gröbner basis block ciphers 0202 electrical engineering electronic engineering information engineering 020201 artificial intelligence & image processing 0101 mathematics Invariant (mathematics) Algorithm Linear equation Mathematics |
| Zdroj: | Fast Software Encryption ISBN: 9783642340468 FSE |
| DOI: | 10.1007/978-3-642-34047-5_18 |
| Popis: | ElimLin is a simple algorithm for solving polynomial systems of multivariate equations over small finite fields. It was initially proposed as a single tool by Courtois to attack DES. It can reveal some hidden linear equations existing in the ideal generated by the system. We report a number of key theorems on ElimLin. Our main result is to characterize ElimLin in terms of a sequence of intersections of vector spaces. It implies that the linear space generated by ElimLin is invariant with respect to any variable ordering during elimination and substitution. This can be seen as surprising given the fact that it eliminates variables. On the contrary, monomial ordering is a crucial factor in Grobner basis algorithms such as F4. Moreover, we prove that the result of ElimLin is invariant with respect to any affine bijective variable change. Analyzing an overdefined dense system of equations, we argue that to obtain more linear equations in the succeeding iteration in ElimLin some restrictions should be satisfied. Finally, we compare the security of LBlock and MIBS block ciphers with respect to algebraic attacks and propose several attacks on Courtois Toy Cipher version 2 (CTC2) with distinct parameters using ElimLin. |
| Databáze: | OpenAIRE |
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