Paper 2016/248

Invariant subspaces in Simpira

Sondre Rønjom

Abstract

In this short note we report on invariant subspaces in Simpira in the case of four registers. In particular, we show that the whole input space (respectively output space) can be partitioned into invariant cosets of dimension $56$ over $\F_{2^8}^{64}$. These invariant subspaces are found by exploiting the \emph{non-invariant} subspace properties of AES together with the particular choice of Feistel configuration. Though we give the invariant subspaces for $b=4$ in this paper, we remark that there are invariant subspaces in several of the Simpira instances; these can be determined with only minor adjustments to the analysis in this paper.

Note: Short note

Metadata
Available format(s)
PDF
Category
Secret-key cryptography
Publication info
Preprint.
Contact author(s)
sondrer @ gmail com
History
2016-03-06: received
Short URL
https://ia.cr/2016/248
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2016/248,
      author = {Sondre Rønjom},
      title = {Invariant subspaces in Simpira},
      howpublished = {Cryptology ePrint Archive, Paper 2016/248},
      year = {2016},
      note = {\url{https://eprint.iacr.org/2016/248}},
      url = {https://eprint.iacr.org/2016/248}
}
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