Extended Truncated-differential Distinguishers on Round-reduced AES

  • Zhenzhen Bao Division of Mathematical Sciences, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
  • Jian Guo Division of Mathematical Sciences, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
  • Eik List Bauhaus-Universität Weimar, Weimar, Germany
Keywords: Cryptanalysis, AES, Permutation, Collision, Differential, Expectation, Distinguisher

Abstract

Distinguishers on round-reduced AES have attracted considerable attention in the recent years. While the number of rounds covered in key-recovery attacks did not increase, subspace, yoyo, mixture-differential, and multiple-of-n cryptanalysis advanced the understanding of the properties of the cipher.
For substitution-permutation networks, integral attacks are a suitable target for extension since they usually end after a linear layer sums several subcomponents. Based on results by Patarin, Chen et al. already observed that the expected number of collisions for a sum of permutations differs slightly from that for a random primitive. Though, their target remained lightweight primitives.
The present work illustrates how the well-known integral distinguisher on three-round AES resembles a sum of PRPs and can be extended to truncated-differential distinguishers over 4 and 5 rounds. In contrast to previous distinguishers by Grassi et al., our approach allows to prepend a round that starts from a diagonal subspace. We demonstrate how the prepended round can be used for key recovery with a new differential key-recovery attack on six-round AES. Moreover, we show how the prepended round can also be integrated to form a six-round distinguisher. For all distinguishers and the key-recovery attack, our results are supported by implementations with Cid et al.’s established Small-AES version. While the distinguishers do not threaten the security of the AES, they try to shed more light on its properties.

Published
2020-09-28
How to Cite
Bao, Z., Guo, J., & List, E. (2020). Extended Truncated-differential Distinguishers on Round-reduced AES. IACR Transactions on Symmetric Cryptology, 2020(3), 197-261. https://doi.org/10.13154/tosc.v2020.i3.197-261
Section
Articles