IACR News item: 20 July 2015
Nasour Bagheri
ePrint Reportfollow the framework used by Beaulieu et al. from the United States National Security Agency
(NSA) to design SIMON and SPECK. A cipher in this family with K-bit key and N-bit block is
called SIMECKN=K.We show that the security of this block cipher against linear cryptanalysis
is not as good as its predecessors SIMON. More precisely, while the best known linear attack
for SIMON32/64, using algorithm 1 of Matsui, covers 13 rounds we present a linear attack in
this senario which covers 14 rounds of SIMECK32/64. Similarly, using algorithm 1 of Matsui,
we present attacks on 19 and 22 rounds of SIMECK48/96 and SIMECK64/128 respectively,
compare them with known attacks on 16 and 19 rounds SIMON48/96 and SIMON64/128
respectively. In addition, we use algorithm 2 of Matsui to attack 18, 23 and 27 rounds of
SIMECK32/64, SIMECK48/96 and SIMECK64/128 respectively, compare them with known
attacks on 18, 19 and 21 rounds SIMON32/64, SIMON48/96 and SIMON64/128 respectively.
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