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Dynamic Swapping Schemes and Differential Cryptanalysis
Toshinobu KANEKO Kenji KOYAMA Routo TERADA
Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Vol.E77A
No.8
pp.13281336 Publication Date: 1994/08/25
Online ISSN:
DOI:
Print ISSN: 09168508 Type of Manuscript: Special Section PAPER (Special Section on Information Theory and Its Applications) Category: Keyword: differential cryptanalysis, secret key cryptosystem, DES, characteristic probability, dynamic swapping scheme,
Full Text: PDF(695.7KB)>>
Summary:
This paper proposes a dynamically randomized version of DES (called RDES) in which a inputdependent swapping S_{k}(X) is added onto the right half of the input in each round of DES. This new scheme decreases the probability of success in differential cryptanalysis because it decreases the characteristic probability. Each "best" tworound characteristic probability is analyzed for typical schemes of the RDES: (i) RDES1 with a simple onelevel swapping, (ii) RDES1' with an optimal onelevel swapping, (iii) RDES2 with a simple twolevel swapping, and (iv) RDES2' with an optimal twolevel swapping. The main results are as follows. (a) The differential attacks on the 16round RDES1' and the 16round RDES2 require more computational time than the exhaustive search. (b) A differential attack is substantially inapplicable to the 16round RDES2' because more than 2^{63} chosen plaintext pairs are required. (c) The encryption/decryption speed of the nround RDES is almost the same as that of the nround DES.

