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From the world's most renowned security technologist, Bruce Schneier, this 20th Anniversary Edition is the most definitive reference on cryptography ever published and is the seminal work on cryptography. Cryptographic techniques have applications far beyond the obvious uses of encoding and decoding information. For developers who need to know about capabilities, such as digital signatures, that depend on cryptographic techniques, there's no better overview than Applied Cryptography, the definitive book on the subject. Bruce Schneier covers general classes of cryptographic protocols and then specific techniques, detailing the inner workings of real-world cryptographic algorithms including the Data Encryption Standard and RSA public-key cryptosystems. The book includes source-code listings and extensive advice on the practical aspects of cryptography implementation, such as the importance of generating truly random numbers and of keeping keys secure.
". . .the best introduction to cryptography I've ever seen. . . .The book the National Security Agency wanted never to be published. . . ." -Wired Magazine
". . .monumental . . . fascinating . . . comprehensive . . . the definitive work on cryptography for computer programmers . . ." -Dr. Dobb's Journal
". . .easily ranks as one of the most authoritative in its field." -PC Magazine
The book details how programmers and electronic communications professionals can use cryptography-the technique of enciphering and deciphering messages-to maintain the privacy of computer data. It describes dozens of cryptography algorithms, gives practical advice on how to implement them into cryptographic software, and shows how they can be used to solve security problems. The book shows programmers who design computer applications, networks, and storage systems how they can build security into their software and systems.
With a new Introduction by the author, this premium edition will be a keepsake for all those committed to computer and cyber security.
Bruce Schneier is an internationally renowned security technologist, called a "security guru" by The Economist. He is the author of twelve books—including his seminal work, Applied Cryptography: Protocols, Algorithms, and Source Code in C, and Secrets & Lies: Digital Security in a Networked World as well as hundreds of articles, essays, and academic papers. His influential newsletter "Crypto-Gram" and blog "Schneier on Security" are read by over 250,000 people. Schneier is a fellow at the Berkman Center for Internet and Society at Harvard Law School, a program fellow at the New America Foundation's Open Technology Institute, a board member of the Electronic Frontier Foundation, and an Advisory Board member of the Electronic Privacy Information Center. He is also the Chief Technology Officer of Resilient Systems, Inc. You can read his blog, essays, andacademic papers at www.schneier.com. He tweets at @schneierblog.
CONTENTS
INTRODUCTION XIII
FOREWORD BY WHITFIELD DIFFIE XVII
PREFACE XXI
HOW TO READ THIS BOOK XXII
ACKNOWLEDGMENTS XXIV
ABOUT THE AUTHOR XXV
1 FOUNDATIONS 7
1.1 TERMINOLOGY 1
1 .2 STEGANOGRAPHY 9
1.3 SUBSTITUTION CIPHERS AND TRANSPOSITION CIPHERS 10
1.4 SIMPLE XOR 13
1.5 ONE-TIME PADS 15
1.6 COMPUTER ALGORITHMS 17
1.7 LARGE NUMBERS 17
PART I CRYPTOGRAPHIC PROTOCOLS
2 PROTOCOL BUILDING BLOCKS 27
2.1 INTRODUCTION TO PROTOCOLS 21
2.2 COMMUNICATIONS USING SYMMETRIC CRYPTOGRAPHY 28
2.3 ONE-WAY FUNCTIONS 29
2.4 ONE-WAY HASH FUNCTIONS 30
2.5 COMMUNICATIONS USING PUBLIC-KEY CRYPTOGRAPHY 31
2.6 DIGITAL SIGNATURES 34
2.7 DIGITAL SIGNATURES WITH ENCRYPTION 47
2.8 RANDOM AND PSEUDO-RANDOM SEQUENCE GENERATION 44
3 BASIC PROTOCOLS 47
3.1 KEY EXCHANGE 47
3.2 AUTHENTICATION 52
3.3 AUTHENTICATION AND KEY EXCHANGE 56
3.4 FORMAL ANALYSIS OF AUTHENTICATION AND KEY-EXCHANGE PROTOCOLS 65
3.5 MULTIPLE-KEY PUBLIC-KEY CRYPTOGRAPHY 68
3.6 SECRET SPLITTING 70
3.7 SECRET SHARING 71
3.8 CRYPTOGRAPHIC PROTECTION OF DATABASES 73
4 INTERMEDIATE PROTOCOLS 75
4.1 TIMESTAMPING SERVICES 75
4.2 SUBLIMINAL CHANNEL 79
4.3 UNDENIABLE DIGITAL SIGNATURES 81
4.4 DESIGNATED CONFIRMER SIGNATURES 82
4.5 PROXY SIGNATURES 83
4.6 GROUP SIGNATURES 84
4.7 FAIL-STOP DIGITAL SIGNATURES 85
4.8 COMPUTING WITH ENCRYPTED DATA 85
4.9 BIT COMMITMENT 86
4.10 FAIR COIN FLIPS 89
4.11 MENTAL POKER 92
4.12 ONE-WAY ACCUMULATORS 95
4.13 ALL-OR-NOTHING DISCLOSURE OF SECRETS 96
4.14 KEY ESCROW 97
5 ADVANCED PROTOCOLS 101
5.1 ZERO-KNOWLEDGE PROOFS 101
5.2 ZERO-KNOWLEDGE PROOFS OF IDENTITY 109
5.3 BLIND SIGNATURES 112
5.4 IDENTITY-BASED PUBLIC-KEY CRYPTOGRAPHY 115
5.5 OBLIVIOUS TRANSFER 226
5.6 OBLIVIOUS SIGNATURES 227
5.7 SIMULTANEOUS CONTRACT SIGNING 228
5.8 DIGITAL CERTIFIED MAIL 122
5.9 SIMULTANEOUS EXCHANGE OF SECRETS 123
6 ESOTERIC PROTOCOLS 125
6.1 SECURE ELECTIONS 125
6.2 SECURE MULTIPARTY COMPUTATION 234
6.3 ANONYMOUS MESSAGE BROADCAST 237
6.4 DIGITAL CASH 239
PART II CRYPTOGRAPHIC TECHNIQUES
7 KEY LENGTH 151
7.1 SYMMETRIC KEY LENGTH 151
7.2 PUBLIC-KEY KEY LENGTH 158
7.3 COMPARING SYMMETRIC AND PUBLIC-KEY KEY LENGTH 165
7.4 BIRTHDAY ATTACKS AGAINST ONE-WAY HASH FUNCTIONS 165
7.5 HOW LONG SHOULD A KEY BE? 166
7.6 CAVEAT EMETOR 168
8 KEY MANAGEMENT 169
8.1 GENERATING KEYS 170
8.2 NONLINEAR KEYSPACES 175
8.3 TRANSFERRING KEYS 176
8.4 VERIFYING KEYS 178
8.5 USING KEYS 179
8.6 UPDATING KEYS 180
8.7 STORING KEYS 180
8.8 BACKUP KEYS 181
8.9 COMPROMISED KEYS 182
8.10 LIFETIME OF KEYS 183
8.11 DESTROYING KEYS 181
8.12 PUBLIC-KEY KEY MANAGEMENT 185
9 ALGORITHM TYPES AND MODES 189
9.1 ELECTRONIC CODEBOOK MODE 189
9.2 BLOCK REPLAY 191
9.3 CIPHER BLOCK CHAINING MODE 193
9.4 STREAM CIPHERS 197
9.5 SELF-SYNCHRONIZING STREAM CIPHERS 198
9.6 CIPHER-FEEDBACK MODE 200
9.7 SYNCHRONOUS STREAM CIPHERS 202
9.8 OUTPUT-FEEDBACK MODE 203
9.9 COUNTER MODE 205
9.10 OTHER BLOCK-CIPHER MODES 206
9.11 CHOOSING A CIPHER MODE 208
9.12 INTERLEAVING 210
9.13 BLOCK CIPHERS VERSUS STREAM CIPHERS 210
10 USING ALGORITHMS 213
10.1 CHOOSING AN ALGORITHM 214
10.2 PUBLIC-KEY CRYPTOGRAPHY VERSUS SYMMETRIC CRYPTOGRAPHY 216
10.3 ENCRYPTING COMMUNICATIONS CHANNELS 216
10.4 ENCRYPTING DATA FOR STORAGE 220
10.5 HARDWARE ENCRYPTION VERSUS SOFTWARE ENCRYPTION 223
10.6 COMPRESSION, ENCODING, AND ENCRYPTION 226
10.7 DETECTING ENCRYPTION 226
10.8 HIDING CIPHERTEXT IN CIPHERTEXT 227
10.9 DESTROYING INFORMATION 228
PART III CRYPTOGRAPHIC ALGORITHMS
11 MATHEMATICAL BACKGROUND 233
11.1 INFORMATION THEORY 233
11.2 COMPLEXITY THEORY 237
11.3 NUMBER THEORY 242
11.4 FACTORING 255
11.5 PRIME NUMBER GENERATION 258
11.6 DISCRETE LOGARITHMS IN A FINITE FIELD 262
12 DATA ENCRYPTION STANDARD (DES) 265
12.1 BACKGROUND 265
12.2 DESCRIPTION OF DES 270
12.3 SECURITY OF DES 278
12.4 DIFFERENTIAL AND LINEAR CRYPTANALYSIS 285
12.5 THE REAL DESIGN CRITERIA 293
12.6 DES VARIANTS 204
12.7 HOW SECURE IS DES TODAY? 300
13 OTHER BLOCK CIPHERS 303
13.1 LUCIFER 303
13.2 MADRYGA 304
13.3 NEWDES 306
13.4 FEAL 308
13.5 REDOC 311
13.6 LOKI 314
13.7 KHUFU AND KHAFRE 316
13.8 RC2 328
13.9 IDEA 319
13.10 MMB 325
13.11 CA-1.1 327
13.12 SKIPJACK 328
14 STILL OTHER BLOCK CIPHERS 332
14.1 GOST 332
14.2 CAST 334
14.3 BLOWFISH 336
14.4 SAFER 339
14.5 3-WAY 341
14.6 CRAB 342
14.7 SXAL8/MBAL 344
14.8 RC5 344
14.9 OTHER BLOCK ALGORITHMS 346
14.10 THEORY OF BLOCK CIPHER DESIGN 346
14.11 USING ONE-WAY HASH FUNCTIONS 351
14.12 CHOOSING A BLOCK ALGORITHM 354
15 COMBINING BLOCK CIPHERS 357
15.1 DOUBLE ENCRYPTION 357
15.2 TRIPLE ENCRYPTION 358
15.3 DOUBLING THE BLOCK LENGTH 363
15.4 OTHER MULTIPLE ENCRYPTION SCHEMES 363
15.5 CDME KEY SHORTENING 366
15.6 WHITENING 366
15.7 CASCADING MULTIPLE BLOCK ALGORITHMS 367
15.8 COMBINING MULTIPLE BLOCK ALGORITHMS 368
16 PSEUDO-KANDOM-SEQUENCE GENERATORS AND STREAM CIPHERS 369
16.1 LINEAR CONGRUENTIAL GENERATORS 369
16.2 LINEAR FEEDBACK SHIFT REGISTERS 372
16.3 DESIGN AND ANALYSIS OF STREAM CIPHERS 379
16.4 STREAM CIPHERS USING LFSRS 381
16.5 A5 389
16.6 HUGHES XPD/KPD 389
16.7 NANOTEO 390
16.8 RAMBUTAN 390
16.9 ADDITIVE GENERATORS 390
16.10 GIFFORD 392
16.11 ALGORITHM M 393
16.12 PKZ1P 394
17 OTHER STREAM CIPHERS AND REAL RANDOM-SEQUENCE GENERATORS 397
17.1 RC4 397
17.2 SEAL 398
17.3 WAKE 400
17.4 FEEDBACK WITH CARRY SHIFT REGISTERS 402
17.5 STREAM CIPHERS USING FCSRS 405
17.6 NONLINEAR-FEEDBACK SHIFT REGISTERS 412
17.7 OTHER STREAM CIPHERS 413
17.8 SYSTEM-THEORETIC APPROACH TO STREAM-CIPHER DESIGN 415
17.9 COMPLEXITY-THEMATIC APPROACH TO STREAM-CIPHER DESIGN 416
17.10 OTHER APPROACHES TO STREAM-CIPHER DESIGN 418
17.11 CASCADING MULTIPLE STREAM CIPHERS 419
17.12 CHOOSING A STREAM CIPHER 420
17.13 GENERATING MULTIPLE STREAMS FROM A SINGLE PSEUDO-RANDOM-SEQUENCE GENERATOR 420
17.14 REAL RANDOM-SEQUENCE GENERATORS 421
18 ONE-WAY HASH FUNCTIONS 429
18.1 BACKGROUND 429
18.2 SNEFRU 431
18.3 N-HASH 432
18.4 MD4 435
18.5 MD5 436
18.6 MD2 441
18.7 SECURE HASH ALGORITHM (SHA) 441
18.8 RIPE-MD 445
18.9 HAVAL 445
18.10 OTHER ONE-WAY HASH FUNCTIONS 446
18.11 ONE-WAY HASH FUNCTIONS USING SYMMETRIC BLOCK ALGORITHMS 446
18.12 USING PUBLIC-KEY ALGORITHMS 455
18.13 CHOOSING A ONE-WAY HASH FUNCTION 455
18.14 MESSAGE AUTHENTICATION CODES 455
19 PUBLIC-KEY ALGORITHMS 461
19.1 BACKGROUND 461
19.2 KNAPSACK ALGORITHMS 462
19.3 RSA 466
19.4 POHLIG-HELLMAN 474
19.5 RABIN 475
19.6 ELGAMAL 476
19.7 MCELIECE 479
19.8 ELLIPTIC CURVE CRYPTOSYSTEMS 480
19.9 LUC 481
19.10 FINITE AUTOMATON PUBLIC-KEY CRYPTOSYSTEMS 482
20 PUBLIC-KEY DIGITAL SIGNATURE ALGORITHMS 483
20.1 DIGITAL SIGNATURE ALGORITHM [DSA] 483
20.2 DSA VARIANTS 494
20.3 GOST DIGITAL SIGNATURE ALGORITHM 495
20.4 DISCRETE LOGARITHM SIGNATURE SCHEMES 496
20.5 ONG-SCHNORR-SHAMIR 498
20.6 ESIGN 499
20.7 CELLULAR AUTOMATA 500
20.8 OTHER PUBLIC-KEY ALGORITHMS 500
21 IDENTIFICATION SCHEMES 503
21.1 FEIGE-FIAT-SHAMIR 503
21.2 GUTLLOU-QUISQUATER 508
21.3 SCHNORR 510
21.4 CONVERTING IDENTIFICATION SCHEMES TO SIGNATURE SCHEMES 512
22 KEY-EXCHANGE ALGORITHMS 513
22.1 DIFFIE-HELLMAN 513
22.2 STATION-TO-STATION PROTOCOL 516
22.3 SHAMIR'S THREE-PASS PROTOCOL 516
22.4 COMSET 577
22.5 ENCRYPTED KEY EXCHANGE 518
22.6 FORTIFIED KEY NEGOTIATION 522
22.7 CONFERENCE KEY DISTRIBUTION AND SECRET BROADCASTING 523
23 SPECIAL ALGORITHMS FOR PROTOCOLS 527
23.1 MULTIPLE-KEY PUBLIC-KEY CRYPTOGRAPHY 527
23.2 SECRET-SHARING ALGORITHMS 528
23.3 SUBLIMINAL CHANNEL 531
23.4 UNDENIABLE DIGITAL SIGNATURES 536
23.5 DESIGNATED CONFIRMER SIGNATURES 539
23.6 COMPUTING WITH ENCRYPTED DATA 540
23.7 FAIR COIN FLIPS 541
23.8 ONE-WAY ACCUMULATORS 543
23.9 ALL-OR-NOTHING DISCLOSURE OR SECRETS 543
23.10 FAIR AND FAILSAFE CRYPTOSYSTEMS 546
23.11 ZERO-KNOWLEDGE PROOFS OF KNOWLEDGE 548
23.12 BLIND SIGNATURES 549
23.13 OBLIVIOUS TRANSFER 550
23.14 SECURE MULTIPARTY COMPUTATION 552
23.15 PROBABILISTIC ENCRYPTION 552
23.16 QUANTUM CRYPTOGRAPHY 554
PART IV THE REAL WORLD
24 EXAMPLE IMPLEMENTATIONS 561
24.1 IBM SECRET-KEY MANAGEMENT PROTOCOL 561
24.2 MITRENET 562
24.3 ISDN 563
24.4 STU-III 565
24.5 KERBEROS 566
24.6 KRYPTOKNIGHT 572
24.7 SESAME 572
24.8 IBM COMMON CRYPTOGRAPHIC ARCHITECTURE 573
24.9 ISO AUTHENTICATION FRAMEWORK 574
24.10 PRIVACY-ENHANCED MAIL (PEM) 577
24.11 MESSAGE SECURITY PROTOCOL (MSP) 584
24.12 PRETTY GOOD PRIVACY (PGP) 584
24.13 SMART CARDS 587
24.14 PUBLIC-KEY CRYPTOGRAPHY STANDARDS (PKCS) 588
24.15 UNIVERSAL ELECTRONIC PAYMENT SYSTEM (UEPS) 589
24.16 CLIPPER 591
24.17 CAPSTONE 593
24.18 AT&T MODEL 3600 TELEPHONE SECURITY DEVICE (TSD) 594
25 POLITICS 597
25.1 NATIONAL SECURITY AGENCY (NSA) 597
25.2 NATIONAL COMPUTER SECURITY CENTER (NCSC) 599
25.3 NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST) 600
25.4 RSA DATA SECURITY, INC. 603
25.5 PUBLIC KEY PARTNERS 604
25.6 INTERNATIONAL ASSOCIATION FOR CRYPTOGRAPHIC RESEARCH (IACR) 605
25.7 RACE INTEGRITY PRIMITIVES EVALUATION (RIPE) 605
25.8 CONDITIONAL ACCESS FOR EUROPE (CAFE) 606
25.9 ISO/IEC 9979 607
25.10 PROFESSIONAL, CIVIL LIBERTIES, AND INDUSTRY GROUPS 608
25.11 SCICRYPT 608
25.12 CYPHERPUNKS 609
25.13 PATENTS 609
25.14 U.S. EXPORT RULES 610
25.15 FOREIGN IMPORT AND EXPORT OF CRYPTOGRAPHY 617
25.16 LEGAL ISSUES 618
Afterword by Matt Blaze 619
PART V SOURCE CODE
Source Code 623
References 675
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