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Partial Sums Meet FFT: Improved Attack on 6-Round AES

Authors:
Orr Dunkelman , University of Haifa
Shibam Ghosh , University of Haifa
Nathan Keller , Bar Ilan University
Gaetan Leurent , Inria, Paris
Avichai Marmor , Bar Ilan University
Victor Mollimard , University of Haifa
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Presentation: Slides
Conference: EUROCRYPT 2024
Abstract: The partial sums cryptanalytic technique was introduced in 2000 by Ferguson et al., who used it to break 6-round AES with time complexity of $2^{52}$ S-box computations -- a record that has not been beaten ever since. In 2014, Todo and Aoki showed that for 6-round AES, partial sums can be replaced by a technique based on the Fast Fourier Transform (FFT), leading to an attack with a comparable complexity. In this paper we show that the partial sums technique can be combined with an FFT-based technique, to get the best of the two worlds. Using our combined technique, we obtain an attack on 6-round AES with complexity of about $2^{46.4}$ additions. We fully implemented the attack experimentally, along with the partial sums attack and the Todo-Aoki attack, and confirmed that our attack improves the best known attack on 6-round AES by a factor of more than 32. We expect that our technique can be used to significantly enhance numerous attacks that exploit the partial sums technique. To demonstrate this, we use our technique to improve the best known attack on 7-round Kuznyechik by a factor of more than 80, and to reduce the complexity of the best known attack on the full MISTY1 from $2^{69.5}$ to $2^{67}$.
BibTeX
@inproceedings{eurocrypt-2024-33994,
  title={Partial Sums Meet FFT: Improved Attack on 6-Round AES},
  publisher={Springer-Verlag},
  author={Orr Dunkelman and Shibam Ghosh and Nathan Keller and Gaetan Leurent and Avichai Marmor and Victor Mollimard},
  year=2024
}