Code Making and Code Breaking [1 ed.] 1559500344, 9781559500340

Citation preview

fifrtK!fti6 filttF

€88f nftffiKfrtffi

leek fager

Loompanics Unlimited Port Townsend, Washington

:

/ Jack Luger is the author of these fine books available from Loompanics Unlimited:

. . o o

Improvised Weapons in American Prisons How to Use Mail Dropsfor Privacy and hofit Counterfeit I.D. Made Easy The Big Book of Secret Hiding Places

Contents

This book is soldfor informational purposes only. The publisher will not be heU accountable for the use or misuse of the information contnined in this book.

CODE MAKING AND CODE BREAKING @ 1990 by Loompanics Unlimited Printed in USA

All

rights reserved. No part of this book may be reproduced or stored in any form whatsoever without the prior written consent of the publisher. Reviews may quote brief passages without the written consent of the publisher as long :N prop€r credit is given.

Publisltcd by: Loompanics Unlimited

PO Box

ll97

Port Townsend, WA 98368

l. Introduction.... 2. History 3. Secret Writing: The Basics 4. Substitution Ciphers 5. Electro-Mechanical Crphen 6. Transposition Ciphers..... 7. Codes 8. Code-Breaking ... 9. Quasi-Cryptosystems 10. Communication Security Index

Cover and Illustrations by Kevin Martin

ISBN l-55950-034-4 Library of Congress Catalog Card Number 90-06021

.....

..'...1 .........5 .......9 ......21 -....47 .

'....57

'..63 -.. -.....71 ....103 .... . .109

ll9

Introduction I

I Introduction

'l'his is a practical handbook on how to make your own codes und how to "breakn' other peoples' codes. You'll find enough thcory in this book to give you a good background regarding Irow and why codes work, but the emphasis is on practical topics so that you can put this knowledge to work as quickly as gxrssible.

It's necessary to skim over the history and development of crdes and ciphers, to place the subject in perspective and to provide indications of what's been tried before. Some efforts failed nriserably, while others were unqualified successes. Some "crypto" efforts affected history. We don't know about many of these efforts because governments are very secretive regarding their crypto work. Most of whafs going on tday in the many cryptographic struggles between governments affects us directly nnd indirectly, but is likely to remain secret during our lifetimes. There's a very definite and solid reason why cryptographic sccrets are the most closely-guarded, even more than those involving nuclear weapons. Anyone who manages to steal nuclear weapons information has only that. Everything else in the secret world is still locked away from him. With the codes and ciphers,

hc has access to all secret communications. This enables

\

2

CODE MAKING AND CODE BREAKING

penetrating the secrecy surrounding many areas. However, the areas that governments choose to keep secret may surprise some. For example, there's absolutely no secret about the "unbreakable" code or cipher. These exist, and the technology for producing them has been with us for at least six decades. Many governments use unbreakable ciphers. Code-breaking, or cryptanalysis, as we shall see, is the most secret activity of all. The ability to "read" another country's traffic is priceless in many cases, and governments not only jealously guard their techniques, but the very fact that they have them. Codes have been in use for thousands of years. If there's a need to keep a secret, someone will think of a way to record it so that it can't be read by those not in the know. Some of the people who invented codes were naive, and didn't realize that what seemed to be an unbreakable code to them was simple for another to crack wide open. At the time, however, most people were illiterate, and anything written was incomprehensible to them. Those who could read were very unsophisticated regarding codes and ciphers, and consequently many simple-minded ciphers were secure from the opposition.

Today, with the experience of centuries to guide us, we can avoid many common mistakes. We also have some new technical aids which were unavailable only a few years ago, and which, when properly used, can make codes extremely difficult to break.

Not all codes are equally easy to decipher. The major factor in the decision to adopt a particular system is not whether or not it's absolutely unbreakable, but whether the opposition has the ability to break it, or whether they can break it in time to do them any good.

The secrecy penetrators in our society have been welldocumented. Private parties snoop on individuals. Governments snoop on individuals and on each other. Organizations, such as employers and labor unions, use espionage and various forms of

Introduction 3

wrrcttpping and electronic "bugging" to intercept communicaIrons. Any radio transmission can be overheard.

ll'you have a need to keep your communications secret, read tlris book carefully. In these pages you'll find a description of rrrnrry practical systems for hiding the meanings of your mesrurgt:s. You'll find a description and objective appraisal of each orrt:. Some are very secure, but hard to use. Othen require costly

t'tluipment, and we won't waste much time with these. Still olhcrs are workable if your opponent's not too bright, but no prxnl against a sophisticated adversary. A few offer good security rrntl case of use. With this affay, you should have no problem nr sctting up a code system to meet your needs. This is a nutsnrrtl-bolts book, designed to allow the reader to start off with as lrttlt: difficulty as possible. 'l'his is why many of the exotic ciphers and codes are not in this book. We'll discuss briefly various electro-mechanical enlryption machines, but keep in mind that they're practical only hrr governments and corporations because of their high cost.

Some

of

these beautifully intricate crypto-systems are too to be practical. The mathematical "gltcing" equatior^rs are elegant, but truly impractical for the tkrwn and dirty conditions in which most of us have to use \ccrccy. Likewise, there are encryption and decryption methods ntllptable to the home computer, but not everyone has a coml)utcr or the knowledge to use one in a way suitable for cryptogrlphy. In any case, this information is available elsewhere. 'fhere is no glossary of technical terms here. If you're new to clabrd&:.)Z>'ri4O ZZ&O>.eO!EceE >YlrrrcqOED*ca >hrrlA>>DADN|1C&21-EtL>< ,ait(,AF0tLFag)xE])-:-zo'.

EocaqJL)>ElD(/)}. '>>AXIEI&EOO l&>rL*/rnaoiEF BoONzOrr{Obrri !5 I&Eurca>,FI&lZO iQnE!E