Extended Truncated-differential Distinguishers on Round-reduced AES
DOI:
https://doi.org/10.13154/tosc.v2020.i3.197-261Keywords:
Cryptanalysis, AES, Permutation, Collision, Differential, Expectation, DistinguisherAbstract
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.
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Copyright (c) 2020 Zhenzhen Bao, Jian Guo, Eik List
This work is licensed under a Creative Commons Attribution 4.0 International License.