Attacking 44 Rounds of the SHACAL-2 Block Cipher Using Related-Key Rectangle Cryptanalysis

Jiqiang LU; Jongsung KIM

doi:10.1093/ietfec/e91-a.9.2588

Attacking 44 Rounds of the SHACAL-2 Block Cipher Using Related-Key Rectangle Cryptanalysis

Jiqiang LU, Jongsung KIM

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SHACAL-2 is a 64-round block cipher with a 256-bit block size and a variable length key of up to 512 bits. It is a NESSIE selected block cipher algorithm. In this paper, we observe that, when checking whether a candidate quartet is useful in a (related-key) rectangle attack, we can check the two pairs from the quartet one after the other, instead of checking them simultaneously; if the first pair does not meet the expected conditions, we can discard the quartet immediately. We next exploit a 35-round related-key rectangle distinguisher with probability 2^-460 for the first 35 rounds of SHACAL-2, which is built on an existing 24-round related-key differential and a new 10-round differential. Finally, taking advantage of the above observation, we use the distinguisher to mount a related-key rectangle attack on the first 44 rounds of SHACAL-2 . The attack requires 2²³³ related-key chosen plaintexts, and has a time complexity of 2^497.2 computations. This is better than any previously published cryptanalytic results on SHACAL-2 in terms of the numbers of attacked rounds.

Publication: IEICE TRANSACTIONS on Fundamentals Vol.E91-A No.9 pp.2588-2596

Publication Date: 2008/09/01

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Online ISSN: 1745-1337

DOI: 10.1093/ietfec/e91-a.9.2588

Type of Manuscript: PAPER

Category: Cryptography and Information Security

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Jiqiang LU, Jongsung KIM, "Attacking 44 Rounds of the SHACAL-2 Block Cipher Using Related-Key Rectangle Cryptanalysis" in IEICE TRANSACTIONS on Fundamentals, vol. E91-A, no. 9, pp. 2588-2596, September 2008, doi: 10.1093/ietfec/e91-a.9.2588.
Abstract: SHACAL-2 is a 64-round block cipher with a 256-bit block size and a variable length key of up to 512 bits. It is a NESSIE selected block cipher algorithm. In this paper, we observe that, when checking whether a candidate quartet is useful in a (related-key) rectangle attack, we can check the two pairs from the quartet one after the other, instead of checking them simultaneously; if the first pair does not meet the expected conditions, we can discard the quartet immediately. We next exploit a 35-round related-key rectangle distinguisher with probability 2^-460 for the first 35 rounds of SHACAL-2, which is built on an existing 24-round related-key differential and a new 10-round differential. Finally, taking advantage of the above observation, we use the distinguisher to mount a related-key rectangle attack on the first 44 rounds of SHACAL-2 . The attack requires 2²³³ related-key chosen plaintexts, and has a time complexity of 2^497.2 computations. This is better than any previously published cryptanalytic results on SHACAL-2 in terms of the numbers of attacked rounds.
URL: https://global.ieice.org/en_transactions/fundamentals/10.1093/ietfec/e91-a.9.2588/_p

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@ARTICLE{e91-a_9_2588,
author={Jiqiang LU, Jongsung KIM, },
journal={IEICE TRANSACTIONS on Fundamentals},
title={Attacking 44 Rounds of the SHACAL-2 Block Cipher Using Related-Key Rectangle Cryptanalysis},
year={2008},
volume={E91-A},
number={9},
pages={2588-2596},
abstract={SHACAL-2 is a 64-round block cipher with a 256-bit block size and a variable length key of up to 512 bits. It is a NESSIE selected block cipher algorithm. In this paper, we observe that, when checking whether a candidate quartet is useful in a (related-key) rectangle attack, we can check the two pairs from the quartet one after the other, instead of checking them simultaneously; if the first pair does not meet the expected conditions, we can discard the quartet immediately. We next exploit a 35-round related-key rectangle distinguisher with probability 2^-460 for the first 35 rounds of SHACAL-2, which is built on an existing 24-round related-key differential and a new 10-round differential. Finally, taking advantage of the above observation, we use the distinguisher to mount a related-key rectangle attack on the first 44 rounds of SHACAL-2 . The attack requires 2²³³ related-key chosen plaintexts, and has a time complexity of 2^497.2 computations. This is better than any previously published cryptanalytic results on SHACAL-2 in terms of the numbers of attacked rounds.},
keywords={},
doi={10.1093/ietfec/e91-a.9.2588},
ISSN={1745-1337},
month={September},}

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TY - JOUR
TI - Attacking 44 Rounds of the SHACAL-2 Block Cipher Using Related-Key Rectangle Cryptanalysis
T2 - IEICE TRANSACTIONS on Fundamentals
SP - 2588
EP - 2596
AU - Jiqiang LU
AU - Jongsung KIM
PY - 2008
DO - 10.1093/ietfec/e91-a.9.2588
JO - IEICE TRANSACTIONS on Fundamentals
SN - 1745-1337
VL - E91-A
IS - 9
JA - IEICE TRANSACTIONS on Fundamentals
Y1 - September 2008
AB - SHACAL-2 is a 64-round block cipher with a 256-bit block size and a variable length key of up to 512 bits. It is a NESSIE selected block cipher algorithm. In this paper, we observe that, when checking whether a candidate quartet is useful in a (related-key) rectangle attack, we can check the two pairs from the quartet one after the other, instead of checking them simultaneously; if the first pair does not meet the expected conditions, we can discard the quartet immediately. We next exploit a 35-round related-key rectangle distinguisher with probability 2^-460 for the first 35 rounds of SHACAL-2, which is built on an existing 24-round related-key differential and a new 10-round differential. Finally, taking advantage of the above observation, we use the distinguisher to mount a related-key rectangle attack on the first 44 rounds of SHACAL-2 . The attack requires 2²³³ related-key chosen plaintexts, and has a time complexity of 2^497.2 computations. This is better than any previously published cryptanalytic results on SHACAL-2 in terms of the numbers of attacked rounds.
ER -