Linear Cryptanalysis of FEAL

Kazumaro AOKI  Kazuo OHTA  Shiho MORIAI  Mitsuru MATSUI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E81-A    No.1    pp.88-97
Publication Date: 1998/01/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security)
linear cryptanalysis,  1R-attack,  2R-attack,  effective key bits,  effective text bits,  FEAL,  

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This paper applies linear cryptanalysis to FEAL and describes the experimental results of attacking FEAL-8 by linear cryptanalysis. The following points are important in linear cryptanalysis to reduce the processing amount and memory size in the attack: 1) to find linear expressions with as high a deviation as possible, and 2) to reduce the number of effective key bits and effective text bits. We have succeeded in attacking FEAL-8 in about 1 hour on a low-end workstation (SPARCstation 10 Model 30). We have confirmed that the entire set of subkeys of FEAL-8 can be derived from 225 known plaintexts with a success rate of over 70%, and from 226 known plaintexts with a success rate of almost 100%.