New Proposal and Comparison of Closure Tests--More Efficient than the CRYPTO'92 Test for DES--

Kazuo OHTA

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E77-A    No.1    pp.15-19
Publication Date: 1994/01/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security)
switching closure test (SCT),  cycling closure test (CCT),  meet-in-the-middle closure test (MCT),  DES cipher,  

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The well-known closure tests, the cycling closure test (CCT) and the meet-in-the-middle closure test (MCT), were introduced by Kaliski, Rivest and Sherman to analyze the algebraic properties of cryptosystems, and CCT indicates that DES is not closed. Though Coppersmith presented that DES can be proved not to be closed by a particular way, the closure tests can check various kinds of cryptosystems generally. Thus, successors to MCT and CCT have been proposed at CRYPTO. This paper expands the MCT successor, the switching closure test (SCT), to apply to the DES-like cryptosystems, and shows that this SCT variant is more efficient than the closure test proposed at CRYPTO'92, because the SCT variant establishes a better relationship between the computation cost and the probability of error (the evaluation index). The MCT successors are more important than the CCTs, because the MCTs can directly break closed cryptosystemes. Therefore, if you want to detect the closure property of cryptosystems generally, the SCT variant is better.