IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
Online ISSN : 1745-1337
Print ISSN : 0916-8508
Regular Section
New Differential Cryptanalytic Results for Reduced-Round CAST-128
Meiqin WANGXiaoyun WANGKam Pui CHOWLucas Chi Kwong HUI
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2010 Volume E93.A Issue 12 Pages 2744-2754


CAST-128 is a block cipher used in a number of products, notably as the default cipher in some versions of GPG and PGP. It has been approved for Canadian government use by the Communications Security Establishment. Haruki Seki et al. found 2-round differential characteristics and they can attack 5-round CAST-128. In this paper, we studied the properties of round functions F1 and F3 in CAST-128, and identified differential characteristics for F1 round function and F3 round function. So we identified a 6-round differential characteristic with probability 2-53 under 2-23.8 of the total key space. Then based on 6-round differential characteristic, we can attack 8-round CAST-128 with key sizes greater than or equal to 72bits and 9-round CAST-128 with key sizes greater than or equal to 104bits. We give the summary of attacks on reduced-round CAST-128 in Table 10.

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© 2010 The Institute of Electronics, Information and Communication Engineers
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