Abstract
Recently, Courtois and Pieprzyk proposed a class of algebraic attacks on symmetric block ciphers that takes advantage of a previously-unexploited property of substitution boxes, or s-boxes, in the round function. This paper gives a brief overview of this ``overdefined system of equations'' (OSE) attack and shows how the attack may be avoided through the use of round functions constructed according to the CAST design procedure. Such round functions contain a variety of protection mechanisms, including s-boxes of large dimension, a circular key-dependent rotation step, and combinations of operators from different algebraic groups.
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Adams, C. Designing against a class of algebraic attacks on symmetric block ciphers. AAECC 17, 17–27 (2006). https://doi.org/10.1007/s00200-006-0194-3
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DOI: https://doi.org/10.1007/s00200-006-0194-3