## Cryptology ePrint Archive: Report 2016/493

Partition-Based Trapdoor Ciphers

Arnaud Bannier and Nicolas Bodin and Eric Filiol

Abstract: This paper deals with block ciphers embedding a trapdoor which consists to map a partition of the plaintext space to a partition of the ciphertext space. In a first part, this issue is reduced to the study of the S-boxes of the cipher satisfying a few criteria. Then, differential and linear properties of such S-boxes are assessed and an algorithm to build optimal S-boxes is provided. Finally, these primitives are used to design a small trapdoor cipher resistant to linear and differential cryptanalysis. This trapdoor allows to recover the $\kappa$-bit master key with only one plaintext/ciphertext pair and an effort of $2^{\frac{\kappa}{2}}$ encryptions.

Category / Keywords: foundations / Cryptanalysis, block cipher, Substitution-Permutation Network, Trapdoor, Partition, S-box

Date: received 20 May 2016, last revised 26 Aug 2016

Contact author: bannier at esiea fr

Available format(s): PDF | BibTeX Citation

Note: Typos corrected. Minor corrections and revision to improve readability

Short URL: ia.cr/2016/493

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