Technical Report CS0817

In this paper we improve Davies' attack [2] on DES to become capable of breaking the full 16-round DES faster than the exhaustive search. Our attack requires 2^{50} complexity of the data collection and 2^{50} the complexity of analysis. An alternative approach finds 24 key bits of DES with 2^{52} known plaintexts and the data analysis requires only several minutes on a SPARC. Therefore, this is the third successful attack on DES, faster than brute force, after differential cryptanalysis [1] and linear cryptanalysis [5]. We also suggest criteria which make the S-boxes immune to this attack.