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Paper: A note on Weak Keys of PES, IDEA and some Extended Variants

Authors:
Jorge Nakahara Jr
Bart Preneel
Joos Vandewalle
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URL: http://eprint.iacr.org/2002/152
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Abstract: This paper presents an analysis of the PES cipher in a similar setting as done by Daemen et al. at Crypto'93 for IDEA. The following results were obtained for 8.5 round PES: a linear weak-key class of size $2^{48}$; two distinct differential weak-key classes of size $2^{41}$; two differential-linear weak-key classes of size $2^{62}$. For 17-round PES (double-PES): a linear weak-key class of size $2^7$, and a differential weak-key class of size $2^7$ were found. Daemen suggested a modified key schedule for IDEA in order to avoid weak keys. We found a differential weak-key class of size $2^{83}$ for 2.5-round IDEA under his redesigned key schedule, and differential-linear relations for 3.5-round IDEA.
BibTeX
@misc{eprint-2002-11675,
  title={A note on Weak Keys of PES, IDEA and some Extended Variants},
  booktitle={IACR Eprint archive},
  keywords={secret-key cryptography / cryptanalysis, block ciphers},
  url={http://eprint.iacr.org/2002/152},
  note={ jorge.nakahara@esat.kuleuven.ac.be 11967 received 7 Oct 2002},
  author={Jorge Nakahara Jr and Bart Preneel and Joos Vandewalle},
  year=2002
}