Improved SQUARE Attacks against Reduced-Round HIEROCRYPT
Paulo S. L. M. Barreto, Vincent Rijmen, Jorge Nakahara, Bart Preneel, Joos P. L. Vandewalle, Hae Yong Kim · 2002
We present improved SQU.aw, attacks against the NESSIE candidate block ciphers HIEROCRYPT-3 and HIEROCRYPT-L1, designed by Toshiba. We improve over the previous best known attack on 2.5 rounds of HIEROCRYPT-3 by a factor of 2 28 computational steps with an attack on 3 rounds for 128-bit keys, and extend it to 3.5 rounds for longer keys. For HIEROCRYPT-L1 we are able to attack up to 3.5 out of 6.5 rounds.