Understanding Cryptography

by Paar, Christof; Pelzl, Jan; Preneel, Bart

• ISBN13: 9783642041006
• ISBN10: 3642041000
• Format: Hardcover
• Copyright: 2010-02-03
• Publisher: Springer-Verlag New York Inc

Summary

Cryptography is now ubiquitous ' moving beyond the traditional environments, such as government communications and banking systems, we see cryptographic techniques realized in Web browsers, e-mail programs, cell phones, manufacturing systems, embedded software, smart buildings, cars, and even medical implants. Today's designers need a comprehensive understanding of applied cryptography.After an introduction to cryptography and data security, the authors explain the main techniques in modern cryptography, with chapters addressing stream ciphers, the Data Encryption Standard (DES), the Advanced Encryption Standard (AES), block ciphers, public-key cryptography, the RSA cryptosystem, public-key cryptosystems based on the discrete logarithm problem, elliptic-curve cryptosystems, digital signatures, hash functions, Message Authentication Codes (MACs), and methods for key establishment, including certificates and public-key infrastructure (PKI). Throughout the book, the authors focus on communicating the essentials and keeping the mathematics to a minimum, and they move quickly from explaining the foundations to describing practical implementations, including recent topics such as lightweight ciphers for RFIDs and mobile devices.The authors have considerable experience teaching applied cryptography to engineering and computer science students and to design professionals, and they make extensive use of boxed definitions, examples, problems, and chapter reviews, while the book's website offers slides, projects and links to further resources. This is a suitable textbook for graduate and advanced undergraduate courses and also for self-study by engineers.

Table of Contents

Introduction to Cryptography and Data Security	p. 1
Overview of Cryptography (and This Book)	p. 2
Symmetric Cryptography	p. 4
Basics	p. 4
Simple Symmetric Encryption: The Substitution Cipher	p. 6
Cryptanalysis	p. 9
General Thoughts on Breaking Cryptosystems	p. 9
How Many Key Bits Are Enough?	p. 11
Modular Arithmetic and More Historical Ciphers	p. 13
Modular Arithmetic	p. 13
Integer Rings	p. 16
Shift Cipher (or Caesar Cipher)	p. 18
Affine Cipher	p. 19
Discussion and Further Reading	p. 20
Lessons Learned	p. 22
Problems	p. 24
Stream Ciphers	p. 29
Introduction	p. 30
Stream Ciphers vs. Block Ciphers	p. 30
Encryption and Decryption with Stream Ciphers	p. 31
Random Numbers and an Unbreakable Stream Cipher	p. 34
Random Number Generators	p. 34
The One-Time Pad	p. 36
Towards Practical Stream Ciphers	p. 38
Shift Register-Based Stream Ciphers	p. 41
Linear Feedback Shift Registers (LFSR)	p. 41
Known-Plaintext Attack Against Single LFSRs	p. 45
Trivium	p. 46
Discussion and Further Reading	p. 49
Lessons Learned	p. 50
Problems	p. 52
The Data Encryption Standard (DES) and Alternatives	p. 55
Introduction to DES	p. 56
Confusion and Diffusion	p. 57
Overview of the DES Algorithm	p. 58
Internal Structure of DES	p. 61
Initial and Final Permutation	p. 61
The â-Function	p. 62
Key Schedule	p. 67
Decryption	p. 69
Security of DES	p. 72
Exhaustive Key Search	p. 73
Analytical Attacks	p. 75
Implementation in Software and Hardware	p. 75
DES Alternatives	p. 77
The Advanced Encryption Standard (AES) and the AES Finalist Ciphers	p. 77
Triple DES (3DES) and DESX	p. 78
Lightweight Cipher PRESENT	p. 78
Discussion and Further Reading	p. 81
Lessons Learned	p. 82
Problems	p. 83
The Advanced Encryption Standard (AES)	p. 87
Introduction	p. 88
Overview of the AES Algorithm	p. 89
Some Mathematics: A Brief Introduction to Galois Fields	p. 90
Existence of Finite Fields	p. 90
Prime Fields	p. 93
Extension Fields GF(2m)	p. 94
Addition and Subtraction in GF(2m)	p. 95
Multiplication in GF{2m)	p. 96
Inversion in GF(2m)	p. 98
Internal Structure of AES	p. 99
Byte Substitution Layer	p. 101
Diffusion Layer	p. 103
Key Addition Layer	p. 106
Key Schedule	p. 106
Decryption	p. 110
Implementation in Software and Hardware	p. 115
Discussion and Further Reading	p. 116
Lessons Learned	p. 117
Problems	p. 118
More About Block Ciphers	p. 123
Encryption with Block Ciphers: Modes of Operation	p. 124
Electronic Codebook Mode (ECB)	p. 124
Cipher Block Chaining Mode (CBC)	p. 128
Output Feedback Mode (ORB)	p. 130
Cipher Feedback Mode (CFB)	p. 131
Counter Mode (CTR)	p. 132
Galois Counter Mode (GCM)	p. 134
Exhaustive Key Search Revisited	p. 136
Increasing the Security of Block Ciphers	p. 137
Double Encryption and Meet-in-the-Middle Attack	p. 138
Triple Encryption	p. 140
Key Whitening	p. 141
Discussion and Further Reading	p. 143
Lessons Learned	p. 144
Problems	p. 145
Introduction to Public-Key Cryptography	p. 149
Symmetric vs. Asymmetric Cryptography	p. 150
Practical Aspects of Public-Key Cryptography	p. 153
Security Mechanisms	p. 154
The Remaining Problem: Authenticity of Public Keys	p. 154
Important Public-Key Algorithms	p. 155
Key Lengths and Security Levels	p. 156
Essential Number Theory for Public-Key Algorithms	p. 157
Euclidean Algorithm	p. 157
Extended Euclidean Algorithm	p. 160
Euler's Phi Function	p. 164
Fermat's Little Theorem and Euler's Theorem	p. 166
Discussion and Further Reading	p. 168
Lessons Learned	p. 169
Problems	p. 170
The RSA Cryptosystem	p. 173
Introduction	p. 174
Encryption and Decryption	p. 174
Key Generation and Proof of Correctness	p. 175
Encryption and Decryption: Fast Exponentiation	p. 179
Speed-up Techniques for RSA	p. 183
Fast Encryption with Short Public Exponents	p. 183
Fast Decryption with the Chinese Remainder Theorem	p. 184
Finding Large Primes	p. 187
How Common Are Primes?	p. 187
Primality Tests	p. 188
RSA in Practice: Padding	p. 192
Attacks	p. 194
Implementation in Software and Hardware	p. 197
Discussion and Further Reading	p. 198
Lessons Learned	p. 199
Problems	p. 200
Public-Key Cryptosystems Based on the Discrete Logarithm Problem	p. 205
Difne-Hellman Key Exchange	p. 206
Some Algebra	p. 208
Groups	p. 208
Cyclic Groups	p. 210
Subgroups	p. 214
The Discrete Logarithm Problem	p. 216
The Discrete Logarithm Problem in Prime Fields	p. 216
The Generalized Discrete Logarithm Problem	p. 218
Attacks Against the Discrete Logarithm Problem	p. 219
Security of the Difne-Hellman Key Exchange	p. 225
The Elgamal Encryption Scheme	p. 226
From Difne-Hellman Key Exhange to Elgamal Encryption	p. 226
The Elgamal Protocol	p. 227
Computational Aspects	p. 229
Security	p. 230
Discussion and Further Reading	p. 232
Lessons Learned	p. 233
Problems	p. 234
Elliptic Curve Cryptosystems	p. 239
How to Compute with Elliptic Curves	p. 239
Definition of Elliptic Curves	p. 240
Group Operations on Elliptic Curves	p. 242
Building a Discrete Logarithm Problem with Elliptic Curves	p. 245
Difne-Hellman Key Exchange with Elliptic Curves	p. 249
Security	p. 251
Implementation in Software and Hardware	p. 252
Discussion and Further Reading	p. 253
Lessons Learned	p. 255
Problems256
Digital Signatures	p. 259
Introduction	p. 260
Odd Colors for Cars, or: Why Symmetric Cryptography Is Not Sufficient	p. 260
Principles of Digital Signatures	p. 261
Security Services	p. 263
The RSA Signature Scheme	p. 264
Schoolbook RSA Digital Signature	p. 265
Computational Aspects	p. 267
Security	p. 267
The Elgamal Digital Signature Scheme	p. 270
Schoolbook Elgamal Digital Signature	p. 270
Computational Aspects	p. 273
Security	p. 274
The Digital Signature Algorithm (DSA)	p. 277
The DSA Algorithm	p. 277
Computational Aspects	p. 280
Security	p. 281
The Elliptic Curve Digital Signature Algorithm (ECDSA)	p. 282
The ECDSA Algorithm	p. 282
Computational Aspects	p. 285
Security	p. 286
Discussion and Further Reading	p. 287
Lessons Learned	p. 288
Problems	p. 289
Hash Functions	p. 293
Motivation: Signing Long Messages	p. 294
Security Requirements of Hash Functions	p. 296
Preimage Resistance or One-Wayness	p. 297
Second Preimage Resistance or Weak Collision Resistance	p. 297
Collision Resistance and the Birthday Attack	p. 299
Overview of Hash Algorithms	p. 303
Dedicated Hash Functions: The MD4 Family	p. 304
Hash Functions from Block Ciphers	p. 305
The Secure Hash Algorithm SHA-1	p. 307
Preprocessing	p. 308
Hash Computation	p. 309
Implementation	p. 312
Discussion and Further Reading	p. 312
Lessons Learned	p. 313
Problems	p. 315
Message Authentication Codes (MACs)	p. 319
Principles of Message Authentication Codes	p. 320
MACs from Hash Functions: HMAC	p. 321
MACs from Block Ciphers: CBC-MAC	p. 325
Galois Counter Message Authentication Code (GMAC)	p. 327
Discussion and Further Reading	p. 327
Lessons Learned	p. 328
Problems	p. 329
Key Establishment	p. 331
Introduction	p. 332
Some Terminology	p. 332
Key Freshness and Key Derivation	p. 332
The n2 Key Distribution Problem	p. 334
Key Establishment Using Symmetric-Key Techniques	p. 336
Key Establishment with a Key Distribution Center	p. 336
Kerberos	p. 339
Remaining Problems with Symmetric-Key Distribution	p. 341
Key Establishment Using Asymmetric Techniques	p. 342
Man-in-the-Middle Attack	p. 342
Certificates	p. 344
Public-Key Infrastructures (PKI) and CAs	p. 347
Discussion and Further Reading	p. 351
Lssons Learned	p. 352
Problems	p. 353
References	p. 359
Index	p. 367
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