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Cover image for Complexity and cryptography : an introduction
Title:
Complexity and cryptography : an introduction
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Publication Information:
UK : Cambridge University Press, 2006
Physical Description:
xii, 292 p. : ill. ; 24 cm.
ISBN:
9780521852319
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30000010229202 Z103 T35 2006 Open Access Book Book
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Summary

Summary

Cryptography plays a crucial role in many aspects of today's world, from internet banking and ecommerce to email and web-based business processes. Understanding the principles on which it is based is an important topic that requires a knowledge of both computational complexity and a range of topics in pure mathematics. This book provides that knowledge, combining an informal style with rigorous proofs of the key results to give an accessible introduction. It comes with plenty of examples and exercises (many with hints and solutions), and is based on a highly successful course developed and taught over many years to undergraduate and graduate students in mathematics and computer science.


Author Notes

Dominic Welsh is Professor of Mathematics and Fellow of Merton College, Oxford.


Reviews 1

Choice Review

Talbot (University College London) and Welsh (Merton College, Oxford) emphasize modern cryptology in the light of complexity theory, which is presented first in a rigorous manner, including discussions of many open problems. Not intending to create a comprehensive work, the authors treat classical cryptology very briefly, leave out much cryptanalysis, and skip elliptic curve cryptography and quantum cryptography. Having said this, a great deal is presented and the unique approach makes this work valuable. At times, it is more oriented toward theory than practice. The popular cryptosystems DES and AES are discussed briefly, without details necessary for implementation. The book is based on a course taught to seniors and graduate students, but without an instructor's help, most undergraduates would likely experience difficulty. The mathematics is at a fairly high level and most proofs are included. This is a fine resource for campuses offering cryptology, but it does not serve as the gentlest introduction for students without previous knowledge of the subject. For them, the easier (and much less thorough!) Cryptology by Albrecht Beutelspacher (1994) or Cryptological Mathematics by Robert E. Lewand (CH, Dec'01, 39-2242) is recommended. Those more interested in implementation than theory should seek Bruce Schneier's books. ^BSumming Up: Recommended. Upper-division undergraduates through professionals. C. Bauer York College of Pennsylvania


Table of Contents

Prefacep. ix
Notationp. xi
1 Basics of cryptographyp. 1
1.1 Cryptographic modelsp. 2
1.2 A basic scenario: cryptosystemsp. 3
1.3 Classical cryptographyp. 7
1.4 Modern cryptographyp. 8
2 Complexity theoryp. 10
2.1 What is complexity theory?p. 10
2.2 Deterministic Turing machinesp. 16
2.3 Decision problems and languagesp. 22
2.4 Complexity of functionsp. 30
2.5 Space complexityp. 33
3 Non-deterministic computationp. 39
3.1 Non-deterministic polynomial time - NPp. 39
3.2 Polynomial time reductionsp. 43
3.3 NP-completenessp. 45
3.4 Turing reductions and NP-hardnessp. 54
3.5 Complements of languages in NPp. 56
3.6 Containments between complexity classesp. 60
3.7 NP revisited - non-deterministic Turing machinesp. 62
4 Probabilistic computationp. 67
4.1 Can tossing coins help?p. 67
4.2 Probabilistic Turing machines and RPp. 71
4.3 Primality testingp. 74
4.4 Zero-error probabilistic polynomial timep. 80
4.5 Bounded-error probabilistic polynomial timep. 81
4.6 Non-uniform polynomial timep. 83
4.7 Circuitsp. 86
4.8 Probabilistic circuitsp. 92
4.9 The circuit complexity of most functionsp. 93
4.10 Hardness resultsp. 94
5 Symmetric cryptosystemsp. 99
5.1 Introductionp. 99
5.2 The one time pad: Vernam's cryptosystemp. 101
5.3 Perfect secrecyp. 102
5.4 Linear shift-register sequencesp. 106
5.5 Linear complexityp. 111
5.6 Non-linear combination generatorsp. 113
5.7 Block ciphers and DESp. 115
5.8 Rijndael and the AESp. 118
5.9 The Pohlig-Hellman cryptosystemp. 119
6 One way functionsp. 125
6.1 In search of a definitionp. 125
6.2 Strong one-way functionsp. 129
6.3 One way functions and complexity theoryp. 132
6.4 Weak one-way functionsp. 135
7 Public key cryptographyp. 141
7.1 Non-secret encryptionp. 141
7.2 The Cocks-Ellis non-secret cryptosystemp. 142
7.3 The RSA cryptosystemp. 145
7.4 The Elgamal public key cryptosystemp. 147
7.5 Public key cryptosystems as trapdoor functionsp. 150
7.6 Insecurities in RSAp. 153
7.7 Finding the RSA private key and factoringp. 155
7.8 Rabin's public key cryptosystemp. 158
7.9 Public key systems based on NP-hard problemsp. 161
7.10 Problems with trapdoor systemsp. 164
8 Digital signaturesp. 170
8.1 Introductionp. 170
8.2 Public key-based signature schemesp. 171
8.3 Attacks and security of signature schemesp. 172
8.4 Signatures with privacyp. 176
8.5 The importance of hashingp. 178
8.6 The birthday attackp. 180
9 Key establishment protocolsp. 187
9.1 The basic problemsp. 187
9.2 Key distribution with secure channelsp. 188
9.3 Diffie-Hellman key establishmentp. 190
9.4 Authenticated key distributionp. 193
9.5 Secret sharingp. 196
9.6 Shamir's secret sharing schemep. 197
10 Secure encryptionp. 203
10.1 Introductionp. 203
10.2 Pseudorandom generatorsp. 204
10.3 Hard and easy bits of one-way functionsp. 207
10.4 Pseudorandom generators from hard-core predicatesp. 211
10.5 Probabilistic encryptionp. 216
10.6 Efficient probabilistic encryptionp. 221
11 Identification schemesp. 229
11.1 Introductionp. 229
11.2 Interactive proofsp. 231
11.3 Zero knowledgep. 235
11.4 Perfect zero-knowledge proofsp. 236
11.5 Computational zero knowledgep. 240
11.6 The Fiat-Shamir identification schemep. 246
Appendix 1 Basic mathematical backgroundp. 250
A1.1 Order notationp. 250
A1.2 Inequalitiesp. 250
Appendix 2 Graph theory definitionsp. 252
Appendix 3 Algebra and number theoryp. 253
A3.1 Polynomialsp. 253
A3.2 Groupsp. 253
A3.3 Number theoryp. 254
Appendix 4 Probability theoryp. 257
Appendix 5 Hints to selected exercises and problemsp. 261
Appendix 6 Answers to selected exercises and problemsp. 268
Bibliographyp. 278
Indexp. 287
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