Decrypted Secrets: Methods & Maxims of Cryptology. Springer

Friedrich L. Bauer

4th, Revised & Extended Edition

With 191 Figures, 29 Tables, and 16 Color Plates

Decrypted Secrets
Methods & Maxims of Cryptology

Dr. rer. nat. Dr. ès sc. h.c. Dr. rer. nat. h.c. mult. Friedrich L. Bauer
Professor Emeritus of Mathematics and Computer Science
Munich Institute of Technology
Department of Computer Science
Boltzmannstr. 3
85748 Garching, Germany

__________________________________________________
ACM Computing Classification (1998): E.3, D.4.6, K.6.5, E.4
Mathematics Subject Classification (1991): 94A60, 68P25
_______________________________________
Library of Congress Control Number: 2006933429

ISBN-10 3-540-24502-2 Springer Berlin Heidelberg New York
ISBN-13 978-3-540-24502-5 Springer Berlin Heidelberg New York
ISBN 3-540-42674-4 3rd ed. Springer Berlin Heidelberg New York

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Preface

Towards the end of the 1960s, under the influence of the rapid development
of microelectronics, electromechanical cryptological machines began to be
replaced by electronic data encryption devices using large-scale integrated
circuits. This promised more secure encryption at lower prices. Then, in
1976, Diffie and Hellman opened up the new cryptological field of public-key
systems. Cryptography, hitherto cloaked in obscurity, was emerging into the
public domain. Additionally, ENIGMA revelations awoke the public interest.
Computer science was a flourishing new field, too, and computer scientists
became interested in several aspects of cryptology. But many of them were
not well enough informed about the centuries-long history of cryptology and
the high level it had attained. I saw some people starting to reinvent the
wheel, and others who had an incredibly naive belief in safe encryption,
and I became worried about the commercial and scientific development of
professional cryptology among computer scientists and about the unstable
situation with respect to official security services.

This prompted me to offer lectures on this subject at the Munich Institute of
Technology. The first series of lectures in the winter term 1977/78, backed
by the comprehensive and reliable book The Codebreakers (1967) by David
Kahn, was held under the code name ‘Special Problems of Information
Theory’ and therefore attracted neither too many students nor too many
suspicious people from outside the university.

Next time, in the summer term of 1981, my lectures on the subject were
announced under the open title ‘Cryptology’. This was seemingly the first
publicly announced lecture series under this title at a German, if not indeed
a Continental European, university.

The series of lectures was repeated a few times, and in 1986/87 lecture notes
were printed which finally developed into Part I of this book. Active interest
on the side of the students led to a seminar on cryptanalytic methods in the
summer term of 1988, from which Part II of the present book originated.
The 1993 first edition (in German) of my book Kryptologie, although written
mainly for computer science students, found lively interest also outside the
field. It was reviewed favorably by some leading science journalists, and
the publisher followed the study book edition with a 1995 hardcover edition
under the title Entzifferte Geheimnisse [Decrypted Secrets], which gave me
the opportunity to round out some subjects. Reviews in American journals
recommended also an English version, which led in 1997 to the present book.
It has become customary among cryptologists to explain how they became
acquainted with the field. In my case, this was independent of the Second
World War. In fact, I was never a member of any official service—and I

consider this my greatest advantage, since I am not bound by any pledge of

secrecy. On the other hand, keeping eyes and ears open and reading between

the lines, I learned a lot from conversations (where my scientific metier was

a good starting point), although I never know exactly whether I am allowed

to know what I happen to know.

Luigi Sacco (1883–1970)

It all started in 1951, when I told my former professor

of formal logic at Munich University, Wilhelm Britzelmayr,

of my invention of an error-correcting code

for teletype lines1. This caused him to make a wrong

association, and he gave me a copy of Sacco’s book,

which had just appeared2. I was lucky, for it was the

best book I could have encountered at that time—

although I didn’t know that then. I devoured the

book. Noticing this, my dear friend and colleague

Paul August Mann, who was aware of my acquaintance

with Shannon’s redundancy-decreasing encoding,

gave me a copy of the now-famous paper by

Claude Shannon called Communication Theory of Secrecy Systems3 (which

in those days as a Bell Systems Technical Report was almost unavailable in

Germany). I was fascinated by this background to Shannon’s information

theory, which I was already familiar with. This imprinted my interest in

cryptology as a subfield of coding theory and formal languages theory, fields

that held my academic interest for many years to come.

Strange accidents—or maybe sharper observation—then brought me into

contact with more and more people once close to cryptology, starting with

Willi Jensen (Flensburg) in 1955, Karl Stein (Munich) in 1955, Hans Rohrbach,

my colleague at Mainz University, in 1959, as well as Helmut Grunsky,

Gisbert Hasenj¨ager, and Ernst Witt. In 1957, I became acquainted with

Erich H¨uttenhain (Bad Godesberg), but our discussions on the suitability of

certain computers for cryptological work were in the circumstances limited

by certain restrictions. Among the American and British colleagues in numerical

analysis and computer science I had closer contact with, some had

been involved with cryptology in the Second World War; but no one spoke

about that, particularly not before 1974, the year when Winterbotham’s book

The Ultra Secret appeared. In 1976, I heard B. Randall and I. J. Good reveal

some details about the Colossi in a symposium in Los Alamos. As a scienceoriented

civilian member of the cryptology academia, my interest in cryptology

was then and still is centered on computerized cryptanalysis. Other

aspects of signals intelligence (‘SIGINT’), for example, traffic analysis and direction

finding, are beyond the scope of this book; the same holds for physical

devices that screen electromechanical radiation emitted by cipher machines.

Cryptology is a discipline with an international touch and a particular terminology.

It may therefore be helpful sometimes to give in this book some

explanations of terms that originated in a language other than English.

The first part of this book presents cryptographic methods. The second part

covers cryptanalysis, above all the facts that are important for judging cryptographic

methods and for saving the user from unexpected pitfalls. This

follows from Kerckhoffs’ maxim: Only a cryptanalyst can judge the security

of a cryptosystem. A theoretical course on cryptographic methods alone

seems to me to be bloodless. But a course on cryptanalysis is problematic:

Either it is not conclusive enough, in which case it is useless, or it is conclusive,

but touches a sensitive area. There is little clearance in between. I have

tried to cover at least all the essential facts that are in the open literature or

can be deduced from it. No censorship took place.

Certain difficulties are caused by the fact that governmental restrictions during

and after World War II, such as the ‘need to know’ rule and other gimmicks,

misled even people who had been close to the centers of cryptanalysis.

Examples include the concept of Banburismus and the concept of a ‘cilli’.

The word Banburismus—the name was coined in Britain—was mentioned in

1985 by Deavours and Kruh in their book, but the method was only vaguely

described. Likewise, the description Kahn gave in 1991 in his book is rather

incomplete. On the other hand, in Kozaczuk’s book of 1979 (English edition

of 1984), Rejewski gave a description of R´o˙zycki’s ‘clock method’, which

turned out to be the same—but most of the readers could not know of this

connection. Then, in 1993, while giving a few more details on the method,

Good (in ‘Codebreakers’) confirmed that “Banburism was an elaboration

of ... the clock method ... [of] ... R´o˙zycki”. He also wrote that this elaboration

was ‘invented at least mainly by Turing’, and referred to a sequential

Bayesian process as the “method of scoring”. For lack of declassified concrete

examples, the exposition in Sect. 19.4.2 of the present book, based on the recently

published postwar notes of Alexander and of Mahon and articles by

Erskine and by Noskwith in the recent book Action This Day, cannot yet be

a fully satisfactory one. And as to cillies, even Gordon Welchman admitted

that he had misinterpreted the origin of the word, thinking of ‘silly’. Other

publications gave other speculations, see Sect. 19.7, fn. 29. Ralph Erskine, in

Action This Day, based on the recently declassified ‘Cryptanalytic Report

on the Yellow Machine’, 71-4 (NACP HCC Box 1009, Nr. 3175), gives the

following summary of the method:

‘Discovered by Dilly Knox in late January 1940, cillies reduced enormously

the work involved in using the Zygalski sheets, and after 1 May, when the

Zygalski sheets became useless, they became a vital part of breaking Enigma

by hand during most of 1940. They were still valuable in 1943.

Cillies resulted from a combination of two different mistakes in a multi-part

message by some Enigma operators. The first was their practice of leaving

the rotors untouched when they reached the end of some part of the message.

Since the letter count of each message part was included in the preamble, the

message key of the preceding part could be calculated within fine limits. The

second error was the use of non-random message keys—stereotyped keyboard

touches and 3-letter-acronyms. In combination, and in conjunction with the

different turnover points of rotors I to V, they allowed one to determine which

rotors could, and which could not, be in any given position in the machine.’

Although Banburismus and cillies were highly important in the war, it is

hard to understand why Derek Taunt in 1993 was prevented by the British

censor from telling the true story about cillies. Possibly, the same happened

to Jack Good about Banburismus.

***

My intellectual delight in cryptology found an application in the collection

‘Informatik’ of the Deutsches Museum in Munich which I built up in 1984

–1988, where there is a section on cryptological devices and machines. My

thanks go to the Deutsches Museum for providing color plates of some of the

pieces on exhibit there.

And thanks go to my former students and co-workers in Munich, Manfred

Broy, Herbert Ehler, and Anton Gerold for continuing support over the years,

moreover to Hugh Casement for linguistic titbits, and to my late brotherin-

law Alston S. Householder for enlightenment on my English. Karl Stein

and Otto Leiberich gave me details on the ENIGMA story, and I had fruitful

discussions and exchanges of letters with Ralph Erskine, Heinz Ulbricht, Tony

Sale, Frode Weierud, Kjell-Ove Widman, Otto J. Horak, Gilbert Bloch, Arne

Frans´en, and Fritz-Rudolf G¨untsch. Great help was given to me by Kirk

H. Kirchhofer from Crypto AG, Zug (Switzerland). Hildegard Bauer-Vogg

supplied translations of difficult Latin texts, Martin Bauer, Ulrich Bauer and

Bernhard Bauer made calculations and drawings. Thanks go to all of them.

The English version was greatly improved by J. Andrew Ross, with whom

working was a pleasure. In particular, my sincere thanks go to David Kahn

who encouraged me (“The book is an excellent one and deserves the widest

circulation”) and made quite a number of proposals for improvements of the

text. For the present edition, additional material that has been made public

recently has been included, among others on Bletchley Park, the British attack

on Tunny, Colossus and Max Newman’s pioneering work. Moreover, my

particular thanks go to Ralph Erskine who indefatigably provided me with

a lot of additional information and checked some of the dates and wordings.

In this respect, my thanks also go to Jack Copeland, Heinz Ulbricht, and

Augusto Buonafalce. Finally, I have to thank once more Hans W¨ossner for

a well functioning cooperation of long standing, and the new copy editor

Ronan Nugent for very careful work. The publisher is to be thanked for the

fine presentation of the book. And I shall be grateful to readers who are kind

enough to let me know of errors and omissions.

Grafrath, Spring 2006 

F. L. Bauer

Table of Contents

Part I: Cryptography—The People . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1 Introductory Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

1.1 Cryptography and Steganography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.2 Semagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.3 Open Code: Masking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.4 Cues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.5 Open Code: Veiling by Nulls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.6 Open Code: Veiling by Grilles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

1.7 Classification of Cryptographic Methods . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2 Aims and Methods of Cryptography . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.1 The Nature of Cryptography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.2 Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.3 Cryptosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2.4 Polyphony . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

2.5 Character Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

2.6 Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3 Encryption Steps: Simple Substitution . . . . . . . . . . . . . . . . . . . . . . 44

3.1 Case V (1) −−− W (Unipartite Simple Substitutions) . . . . . . . . . . . . . 44

3.2 Special Case V ≺−−−− V (Permutations) . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.3 Case V (1) −−− Wm (Multipartite Simple Substitutions) . . . . . . . . . . . 53

3.4 The General Case V (1) −−− W(m) , Straddling . . . . . . . . . . . . . . . . . . . 55

4 Encryption Steps: Polygraphic Substitution and Coding . 58

4.1 Case V 2 −−− W(m) (Digraphic Substitutions) . . . . . . . . . . . . . . . . . . 58

4.2 Special Cases of Playfair and Delastelle: Tomographic Methods . . . . 64

4.3 Case V 3 −−− W(m) (Trigraphic Substitutions) . . . . . . . . . . . . . . . . . . 68

4.4 The General Case V (n) −−− W(m) : Codes . . . . . . . . . . . . . . . . . . . . . . 68

5 Encryption Steps: Linear Substitution . . . . . . . . . . . . . . . . . . . . . . . . 80

5.1 Self-reciprocal Linear Substitutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

5.2 Homogeneous Linear Substitutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

5.3 Binary Linear Substitutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

5.4 General Linear Substitutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

5.5 Decomposed Linear Substitutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

5.6 Decimated Alphabets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

5.7 Linear Substitutions with Decimal and Binary Numbers . . . . . . . . . 91

6 Encryption Steps: Transposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

6.1 Simplest Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

6.2 Columnar Transpositions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

6.3 Anagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

7 Polyalphabetic Encryption: Families of Alphabets. . . . . . . . .106

7.1 Iterated Substitutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106

7.2 Cyclically Shifted and Rotated Alphabets . . . . . . . . . . . . . . . . . . . . . . . . 107

7.3 Rotor Crypto Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

7.4 Shifted Standard Alphabets: Vigen`ere and Beaufort . . . . . . . . . . . . . 127

7.5 Unrelated Alphabets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131

8 Polyalphabetic Encryption: Keys . . . . . . . . . . . . . . . . . . . . . . . . . . .139

8.1 Early Methods with Periodic Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

8.2 ‘Double Key’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

8.3 Vernam Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

8.4 Quasi-nonperiodic Keys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144

8.5 Machines that Generate Their Own Key Sequences . . . . . . . . . . . . . . . 145

8.6 Off-Line Forming of Key Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

8.7 Nonperiodic Keys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158

8.8 Individual, One-Time Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

8.9 Key Negotiation and Key Management. . . . . . . . . . . . . . . . . . . . . . . . . . .165

9 Composition of Classes of Methods . . . . . . . . . . . . . . . . . . . . . . . . 169

9.1 Group Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

9.2 Superencryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

9.3 Similarity of Encryption Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

9.4 Shannon’s ‘Pastry Dough Mixing’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

9.5 Confusion and Diffusion by Arithmetical Operations. . . . . . . . . . . . . .180

9.6 DES and IDEAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

10 Open Encryption Key Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

10.1 Symmetric and Asymmetric Encryption Methods. . . . . . . . . . . . . . . . .194

10.2 One-Way Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

10.3 RSA Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

10.4 Cryptanalytic Attack upon RSA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

10.5 Secrecy Versus Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

10.6 Security of Public Key Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

11 Encryption Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

11.1 Cryptographic Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

11.2 Maxims of Cryptology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

11.3 Shannon’s Yardsticks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

11.4 Cryptology and Human Rights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

Part II: Cryptanalysis—The Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

12 Exhausting Combinatorial Complexity . . . . . . . . . . . . . . . . . . . . . 237

12.1 Monoalphabetic Simple Encryptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

12.2 Monoalphabetic Polygraphic Encryptions . . . . . . . . . . . . . . . . . . . . . . . . 239

12.3 Polyalphabetic Encryptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

12.4 General Remarks on Combinatorial Complexity . . . . . . . . . . . . . . . . . . 244

12.5 Cryptanalysis by Exhaustion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .244

12.6 Unicity Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

12.7 Practical Execution of Exhaustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

12.8 Mechanizing the Exhaustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

13 Anatomy of Language: Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

13.1 Invariance of Repetition Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

13.2 Exclusion of Encryption Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

13.3 Pattern Finding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.4 Finding of Polygraphic Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

13.5 The Method of the Probable Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

13.6 Automatic Exhaustion of the Instantiations of a Pattern . . . . . . . . . 264

13.7 Pangrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

14 Polyalphabetic Case: Probable Words . . . . . . . . . . . . . . . . . . . . . 268

14.1 Non-Coincidence Exhaustion of Probable Word Position . . . . . . . . . 268

14.2 Binary Non-Coincidence Exhaustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . .271

14.3 The De Viaris Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

14.4 Zig-Zag Exhaustion of Probable Word Position . . . . . . . . . . . . . . . . . . . 280

14.5 The Method of Isomorphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

14.6 A clever brute force method: EINSing. . . . . . . . . . . . . . . . . . . . . . . . . . . .287

14.7 Covert Plaintext-Cryptotext Compromise . . . . . . . . . . . . . . . . . . . . . . . . 288

15 Anatomy of Language: Frequencies . . . . . . . . . . . . . . . . . . . . . . . . 290

15.1 Exclusion of Encryption Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

15.2 Invariance of Partitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

15.3 Intuitive Method: Frequency Profile. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293

15.4 Frequency Ordering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294

15.5 Cliques and Matching of Partitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297

15.6 Optimal Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

15.7 Frequency of Multigrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

15.8 The Combined Method of Frequency Matching . . . . . . . . . . . . . . . . . . . 310

15.9 Frequency Matching for Polygraphic Substitutions . . . . . . . . . . . . . . . 316

15.10 Free-Style Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

15.11 Unicity Distance Revisited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318

16 Kappa and Chi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

16.1 Definition and Invariance of Kappa. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

16.2 Definition and Invariance of Chi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

16.3 The Kappa-Chi Theorem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

16.4 The Kappa-Phi Theorem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326

16.5 Symmetric Functions of Character Frequencies . . . . . . . . . . . . . . . . . . 328

17 Periodicity Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

17.1 The Kappa Test of Friedman . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

17.2 Kappa Test for Multigrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

17.3 Cryptanalysis by Machines: Searching for a period . . . . . . . . . . . . . . 333

17.4 Kasiski Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

17.5 Building a Depth and Phi Test of Kullback . . . . . . . . . . . . . . . . . . . . . . 345

17.6 Estimating the Period Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

18 Alignment of Accompanying Alphabets . . . . . . . . . . . . . . . . . . . 350

18.1 Matching the Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350

18.2 Aligning Against Known Alphabet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354

18.3 Chi Test: Mutual Alignment of Accompanying Alphabets. . . . . . . . 358

18.4 Reconstruction of the Primary Alphabet . . . . . . . . . . . . . . . . . . . . . . . . 363

18.5 Kerckhoffs’ Symmetry of Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

18.6 Stripping off Superencryption: Difference Method . . . . . . . . . . . . . . . 370

18.7 Decryption of Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

18.8 Reconstruction of the Password . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

19 Compromises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

19.1 Kerckhoffs’ Superimposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

19.2 Superimposition for Encryptions with a Key Group. . . . . . . . . . . . . . 377

19.3 COLOSSUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

19.4 Adjustment ‘in depth’ of Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412

19.5 Cryptotext-Cryptotext Compromises . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419

19.6 Cryptotext-Cryptotext Compromise: ENIGMAIndicator Doubling 431

19.7 Plaintext-Cryptotext Compromise: Feedback Cycle . . . . . . . . . . . . . . 448

20 Linear Basis Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459

20.1 Reduction of Linear Polygraphic Substitutions. . . . . . . . . . . . . . . . . . . 459

20.2 Reconstruction of the Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460

20.3 Reconstruction of a Linear Shift Register . . . . . . . . . . . . . . . . . . . . . . . . 461

21 Anagramming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

21.1 Transposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

21.2 Double Columnar Transposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

21.3 Multiple Anagramming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

22 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470

22.1 Success in Breaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471

22.2 Mode of Operation of the Unauthorized Decryptor . . . . . . . . . . . . . . 476

22.3 Illusory Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482

22.4 Importance of Cryptology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484

Appendix: Axiomatic Information Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

Bibliography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501

Photo Credits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525

List of Color Plates

Plate A The disk of Phaistos

Plate B Brass cipher disks

Plate C The ‘Cryptograph’ of Wheatstone

Plate D The US Army cylinder device M-94

Plate E The US strip device M-138-T4

Plate F The cipher machine of Kryha

Plate G The Hagelin ‘Cryptographer’ C-36

Plate H The US Army M-209, Hagelin licensed

Plate I The cipher machine ENIGMA with four rotors

Plate K Rotors of the ENIGMA

Plate L The British rotor machine TYPEX

Plate M Uhr box of the German Wehrmacht

Plate N Cipher teletype machine Lorenz SZ 42

Plate O Russian one-time pad

Plate P Modern crypto board

Plate Q CRAY Supercomputers

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Product details

Price
Pages	555 p
File Size	17,598 KB
File Type	PDF format
ISBN-10  ISBN-13	3-540-24502-2  978-3-540-24502-5
Copyright	Springer-Verlag Berlin Heidelberg   1997, 2000, 2002, 2007

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