A Fast Version of the DES and a Password Encryption Algorithm

Citation

• M. Bishop, “A Fast Version of the DES and a Password Encryption Algorithm,” Technical Report 87.18, Research Institute for Advanced Computer Science, NASA Ames Research Center, Moffett Field, CA 94035 (July 1987; revised Aug. 1988)

Paper

• PDF
• PS

Abstract

The Data Encryption Standard is used as the basis for the UNIX password encryption scheme. Some of the security of that scheme depends on the speed of the implementation. This paper presents a mathematical formulation of a fast implementation of the DES in software, discusses how the mathematics can be translated into code, and then analyzes the UNIX password scheme to show how these results can be used to implement it. Experimental results are provided for several computers to show that the given method speeds up the computation of a password by roughly 20 times (depending on the specific computer).

Background

This came out of some password guessing work I did, augmented by an observation from Bob Baldwin (thanks, Bob!—rest in peace)