"The Data Encryption Standard (DES)and its strength against attacks" by D. Coppersmith in IBM J. or R&D, v38#3, May 1994 pp243-250 ..in this paper, we examine one such attempt [to break DES], the method of differential cryptanalysis.... we show some of the safeguards against differential cryptanalysis that were built into the system from the beginning. Disclaimer: The present author participated in the design and test of DES, particularly in the design of the S-boxes and in strengthening them against differential cryptonalysis. Naturally , this author has strong opinions about DES and its history. Any opinions in this paper are those of the author and are not necessarily shared by IBM ************************************************** * Allen J. Baum tel. (408)974-3385 * * Apple Computer, MS/305-3B * * 1 Infinite Loop * * Cupertino, CA 95014 baum@apple.com * **************************************************