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Codes and Ciphers Julius Caesar, the Enigma, and the Internet

[书名]Codes and Ciphers Julius Caesar, the Enigma, and the Internet
[作者]R. F. Churchhouse
[出版社] Cambridge university press  
[出版日期]2004
[关键词] secure communication ,Codes andciphers ,Modular arithmetic ,Julius Caesar ciphers andtheir solution
[ISBN]0-511-04218-3
[内容简介]
Contents
Preface ix
1 Introduction 1
Some aspects of secure communication 1
Julius Caesar’s cipher 2
Some basic definitions 3
Three stages to decryption: identification, breaking andsetting
Codes andciphers 5
Assessing the strengthof a cipher system 7
Error detecting andcorrecting codes 8
Other methods of concealing messages 9
Modular arithmetic 10
Modular additionandsubtractionof letters 11
Gender 11
Endmatter 12
2 FromJulius Caesar to simple substitution 13
Julius Caesar ciphers andtheir solution 13
Simple substitutionciphers 15
Howto solve a simple substitutioncipher 17
Letter frequencies inlanguages other thanEnglish 24
Howmany letters are neededto solve a simple substitutioncipher? 26
3 Polyalphabetic systems 28
Strengthening Julius Caesar: Vigenère ciphers 28
Howto solve a Vigenère cipher 30
Indicators 33
Depths 34
Recognising ‘depths’ 34
Howmuchtext dowe needto solve a Vigenère cipher? 37
Jefferson’s cylinder 37
4 Jigsawciphers 40
Transpositions 40
Simple transposition 40
Double transposition 44
Other forms of transposition 48
Assessment of the security of transpositionciphers 51
Double encipherment ingeneral 52
5 Two-letter ciphers 54
Monographto digraph 54
MDTMciphers 56
Digraphto digraph 58
Playfair encipherment 59
Playfair decipherment 60
Cryptanalytic aspects of Playfair 61
Double Playfair 61
6 Codes 64
Characteristics of codes 64
One-part andtwo-part codes 65
Code plus additive 67
7 Ciphers for spies 72
Stencil ciphers 73
Bookciphers 75
Letter frequencies inbookciphers 79
Solving a bookcipher 79
Indicators 86
Disastrous errors inusing a bookcipher 86
‘Garbo’’s ciphers 88
One-time pad 92
8 Producing randomnumbers andletters 94
Randomsequences 94
Producing randomsequences 95
Coinspinning 95
Throwing dice 96
Lottery type draws 97
Cosmic rays 97
Amplifier noise 97
Pseudo-randomsequences 98
Linear recurrences 99
Using a binary streamof key for encipherment 100
Binary linear sequences as key generators 101
Cryptanalysis of a linear recurrence 104
Improving the security of binary keys 104
Pseudo-randomnumber generators 106
The mid-square method 106
Linear congruential generators 107
9 The Enigma cipher machine 110
Historical background 110
The original Enigma 112
Encipherment using wiredwheels 116
Encipherment by the Enigma 118
The Enigma plugboard 121
The Achilles heel of the Enigma 121
The indicator ‘chains’ inthe Enigma 125
Aligning the chains 128
Identifying R1 andits setting 128
Doubly encipheredEnigma messages 132
The Abwehr Enigma 132
10 The Hagelincipher machine 133
Historical background 133
Structure of the Hagelinmachine 134
Encipherment onthe Hagelin 135
Choosing the cage for the Hagelin 138
The theoretical ‘workfactor’ for the Hagelin 142
Solving the Hagelinfroma stretchof key 143
Additional features of the Hagelinmachine 147
The slide 147
Identifying the slide ina cipher message 148
Overlapping 148
Solving the Hagelinfromcipher texts only 150
11 Beyondthe Enigma 153
The SZ42: a pre-electronic machine 153
Descriptionof the SZ42 machine 155
Encipherment onthe SZ42 155
Breaking andsetting the SZ42 158
Modifications to the SZ42 159
12 Public key cryptography 161
Historical background 161
Security issues 163
Protectionof programs anddata 163
Encipherment of programs, data andmessages 164
The key distributionproblem 166
The Diffie–Hellmankey exchange system 166
Strengthof the Diffie–Hellmansystem 168
13 Encipherment andthe internet 170
Generalisationof simple substitution 170
Factorisationof large integers 171
The standardmethodof factorisation 172
Fermat’s ‘Little Theorem’ 174
The Fermat–Euler Theorem(as neededinthe RSAsystem) 175
Encipherment anddecipherment keys inthe RSAsystem 175
The encipherment anddecipherment processes inthe RSAsystem 178
Howdoes the key-owner reply to correspondents? 182
The Data EncryptionStandard(DES) 183
Security of the DES 184
Chaining 186
Implementationof the DES 186
Using bothRSAandDES 186
Asalutary note 187
Beyondthe DES 187
Authenticationandsignature verification 188
Elliptic curve cryptography 189
Appendix 190
Solutions to problems 218
References 230
Name index 235
Subject index 237
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cool,
but i cannot use it any more.