A Java implementation of a key collision attack on DES suggested by Eli Biham, [1], is discussed. Storage space minimization and fast searching techniques to speed up the attack are described. We also demonstrate the suitability of Java for large data cryptographic attacks and illustrate the extensive cryptographic features of the language. Categories and Subject Descriptors D.3.2 [Programming Languages]: Language Classification—JAVA; E.3 [Data encryption] General Terms Algorithms, Security Keywords DES, Key collision attack