Computer Laboratory

Technical reports

Two cryptographic notes

David Wheeler, Roger Needham

November 1994, 6 pages

Abstract

A large block DES-like algorithm

DES was designed to be slow in software. We give here a DES type of code which applies directly to single blocks comprising two or more words of 32 bits. It is thought to be at least as secure as performing DES separately on two word blocks, and has the added advantage of not requiring chaining etc. It is about 8m/(12+2m) times as fast as DES for an m word block and has a greater gain for Feistel codes where the number of rounds is greater. We use the name GDES for the codes we discuss. The principle can be used on any Feistel code.

TEA, a Tiny Encryption Algorithm

We design a short program which will run on most machines and encypher safely. It uses a large number of iterations rather than a complicated program. It is hoped that it can easily be translated into most languages in a compatible way. The first program is given below. It uses little set up time and does a weak non linear iteration enough rounds to make it secure. There are no preset tables or long set up times. It assumes 32 bit words.

Full text

PDF (0.4 MB)

BibTeX record

@TechReport{UCAM-CL-TR-355,
  author =	 {Wheeler, David and Needham, Roger},
  title = 	 {{Two cryptographic notes}},
  year = 	 1994,
  month = 	 nov,
  url = 	 {http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-355.pdf},
  institution =  {University of Cambridge, Computer Laboratory},
  number = 	 {UCAM-CL-TR-355}
}