The 32nd-order differential attack on MISTY1 without FL functions

Yasutaka Igarashi, Toshinobu Kaneko

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)

Abstract

We found a 32nd-order differential characteristic of MISTY1 without FL functions, which makes the differential of upper 7bit of 64-bit output of the 5th round be zero. By using this characteristic and a linearization technique, we show that 6-round MISTY1 without FL functions can be attacked with 235:5 of chosen plaintexts and 234:3 of computations of FO function. We demonstrate this 6-round attack by a computer simulation. CPU time for the simulation is 2 hours and 35 minutes. This attack reduces the plaintexts to 2:3:5 and the computations to 2:14:9 compared to conventional 6-round attack. We also show that 7-round MISTY1 without FL functions can be attacked with 236:5 of the plaintexts and 2112:0 of the computations by using a combination of the 6-round attack and exhaustive search. This 7-round attack reduces the computations to 2:13:1 although the plaintexts increase 224:6 times. These drastic reductions of the computational costs come from counting up the number of occurrences of ciphertexts, and omitting the ciphertexts occurring even number of times from computation.

Original languageEnglish
Title of host publication2008 International Symposium on Information Theory and its Applications, ISITA2008
DOIs
Publication statusPublished - 1 Dec 2008
Event2008 International Symposium on Information Theory and its Applications, ISITA2008 - Auckland, New Zealand
Duration: 7 Dec 200810 Dec 2008

Publication series

Name2008 International Symposium on Information Theory and its Applications, ISITA2008

Conference

Conference2008 International Symposium on Information Theory and its Applications, ISITA2008
CountryNew Zealand
CityAuckland
Period7/12/0810/12/08

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Igarashi, Y., & Kaneko, T. (2008). The 32nd-order differential attack on MISTY1 without FL functions. In 2008 International Symposium on Information Theory and its Applications, ISITA2008 [4895642] (2008 International Symposium on Information Theory and its Applications, ISITA2008). https://doi.org/10.1109/ISITA.2008.4895642