LINEAR CRYPTANALYSIS OF FEAL

This paper applies linear cryptanalysis to FEAL and describes the expe rimental results of attacking FEAL-8 by linear cryptanalysis. The foll owing points are important in linear cryptanalysis to reduce the proce ssing amount and memory size in the attack: 1) to find linear expressi ons 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 at tacking 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 2(25) known plaintexts with a success rate of o ver 70%, and From 2(26) known plaintexts with a success rate of almost 100%.