Paper 2001/068

SQUARE Attacks on Reduced-Round PES and IDEA Block Ciphers

J. Nakahara Jr, P. S. L. M. Barreto, B. Preneel, J. Vandewalle, and H. Y. Kim


This paper reports on variants of the Square attack applied to reduced-round versions of the PES and IDEA block ciphers. Attacks on 2.5 rounds of IDEA require $3\cdot 2^{16}$ chosen-plaintexts and recover 78 key bits. A new kind of attack, the Square related-key attack, is applied on 2.5 rounds of IDEA and recovers 32 key bits, with 2 chosen-plaintexts and $2^{17}$ related keys. Similar results hold for 2.5 rounds of PES. Implementations of the attacks on 32-bit block mini-versions of both ciphers confirmed the expected computational complexity. Although our attacks do not improve on previous approaches, this report shows new variants of the Square attack on word-oriented block ciphers like IDEA and PES.

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Available format(s)
Secret-key cryptography
Publication info
Published elsewhere. Unknown where it was published
block cipherscryptanalysissecret-key cryptography
Contact author(s)
jorge nakahara @ esat kuleuven ac be
2001-08-22: revised
2001-08-14: received
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      author = {J. Nakahara Jr and P. S. L. M. Barreto and B. Preneel and J. Vandewalle and H. Y. Kim},
      title = {SQUARE Attacks on Reduced-Round PES and IDEA Block Ciphers},
      howpublished = {Cryptology ePrint Archive, Paper 2001/068},
      year = {2001},
      note = {\url{}},
      url = {}
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