How to Strengthen DES-like Cryptosystems against Differential Cryptanalysis

Kenji KOYAMA  Routo TERADA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E76-A   No.1   pp.63-69
Publication Date: 1993/01/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security)
DES,  cryptanalysis,  differential attack,  probabilistic swapping,  

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We propose a new randomized version of DES in which a key-dependent swapping is used to strengthen DES and DES-like cryptosystems against differential cryptanalysis. This new scheme, called RDES, decreases the probability of success in differential attack by decreasing the characteristic probability. The characteristic is the effect of particular differences in plaintext pairs on the differences in the resultant ciphertext pairs. The characteristic probability for the n-round RDES is 2-n+1 times that for the n-round DES. As for the differential cryptanalysis based on characteristics, the 16-round RDES is as strong as the about 20-round DES. Encryption/decryption speed of n-round RDES is almost the same as that of the n-round DES.