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Paper: Forking Tweakable Even-Mansour Ciphers

Authors:
Hwigyeom Kim , Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
Yeongmin Lee , Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
Jooyoung Lee , Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
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DOI: 10.46586/tosc.v2020.i4.71-87
URL: https://tosc.iacr.org/index.php/ToSC/article/view/8748
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Abstract: A forkcipher is a keyed, tweakable function mapping an n-bit input to a 2nbit output, which is equivalent to concatenating two outputs from two permutations. A forkcipher can be a useful primitive to design authenticated encryption schemes for short messages. A forkcipher is typically designed within the iterate-fork-iterate (IFI) paradigm, while the provable security of such a construction has not been widely explored.In this paper, we propose a method of constructing a forkcipher using public permutations as its building primitives. It can be seen as applying the IFI paradigm to the tweakable Even-Mansour ciphers. So our construction is dubbed the forked tweakable Even-Mansour (FTEM) cipher. Our main result is to prove that a (1, 1)-round FTEM cipher (applying a single-round TEM to a plaintext, followed by two independent copies of a single-round TEM) is secure up to 2 2n/3 queries in the ideal permutation model.
BibTeX
@article{tosc-2020-30777,
  title={Forking Tweakable Even-Mansour Ciphers},
  journal={IACR Transactions on Symmetric Cryptology},
  publisher={Ruhr-Universit├Ąt Bochum},
  volume={2020, Issue 4},
  pages={71-87},
  url={https://tosc.iacr.org/index.php/ToSC/article/view/8748},
  doi={10.46586/tosc.v2020.i4.71-87},
  author={Hwigyeom Kim and Yeongmin Lee and Jooyoung Lee},
  year=2020
}