Cryptanalysis of TOYOCRYPT-HS1 Stream Cipher

Miodrag J. MIHALJEVIC  Hideki IMAI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E85-A   No.1   pp.66-73
Publication Date: 2002/01/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security)
stream cipher,  keystream generators,  linear feedback shift registers,  nonlinear filter,  cryptanalysis,  

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It is shown that the effective secret-key size of TOYOCRYPT-HS1 stream cipher is only 96 bits, although the secret key consists of 128 bits. This characteristic opens a door for developing an algorithm for cryptanalysis based on the time-memory-data trade-off with the overall complexity significantly smaller than the exhaustive search over the effective key space.