Slide Attacks with a Known-Plaintext Cryptanalysis

Although many strong cryptanalytic tools exploit weaknesses in the data-randomizing part of a block cipher, relatively few general tools for cryptanalyzing on the other part, the key scheduling part, are known. A slide attack is an instance of attacks exploiting the keyschedule weakness. In this paper, currently proposed slide attacks can be still enhanced so that all currently published known-plaintext analytic technique can be applied to smaller part of a cipher with a weak keyscheduling part. As an example, we demonstrate applications of a slide attack to linear cryptanalysis, a DES variant case. In addition, we also show that our enhancement enables to declassify the unknown primitive used in a block cipher. We test a block cipher, GOST, and show how to de-classify the hidden 4-bit substitution tables.