Decrypted Secrets: Methods and Maxims of Cryptology

In today’s unsafe and increasingly wired world cryptology plays a vital role in protecting communication channels, databases, and software from unwanted intruders. This revised and extended third edition of the classic reference work on cryptology now contains many new technical and biographical details. The first part treats secret codes and their uses - cryptography. The second part deals with the process of covertly decrypting a secret code - cryptanalysis, where particular advice on assessing methods is given. The book presupposes only elementary mathematical knowledge. Spiced with a wealth of exciting, amusing, and sometimes personal stories from the history of cryptology, it will also interest general readers.
Written for:
Scientists, students and practitioners in applied mathematics, computer science and information technology, and the general reader
Table of Contents
Part I: Cryptography The People 1 (232)
1 Introductory Synopsis 9 (17)
1.1 Cryptography and Steganography 9 (1)
1.2 Semagrams 10 (3)
1.3 Open Code: Masking 13 (4)
1.4 Cues 17 (2)
1.5 Open Code: Veiling by Nulls 19 (4)
1.6 Open Code: Veiling by Grilles 23 (1)
1.7 Classification of Cryptographic 24 (2)
Methods
2 Aims and Methods of Cryptography 26 (18)
2.1 The Nature of Cryptography 26 (6)
2.2 Encryption 32 (2)
2.3 Cryptosystems 34 (2)
2.4 Polyphony 36 (3)
2.5 Character Sets 39 (2)
2.6 Keys 41 (3)
3 Encryption Steps: Simple Substitution 44 (14)
3.1 Case V(?)—> W (Unipartite Simple 44 (2)
Substitutions)
3.2 Special Case V [-> V (Permutations) 46 (7)
3.3 Case V(?)—> Wm (Multipartite Simple 53 (2)
Substitutions)
3.4 The General Case V(?0 —> W(m) , 55 (3)
Straddling
4 Encryption Steps: Polygraphic 58 (22)
Substitution and Coding
4.1 Case V? —>W(m) (Digraphic 58 (6)
Substitutions)
4.2 Special Cases of Playfair and 64 (4)
Delastelle: Tomographic Methods
4.3 Case V? —>W(m) (Trigraphic 68 (1)
Substitutions)
4.4 The General Case V(n) —> W(m) : 68 (12)
Codes
5 Encryption Steps: Linear Substitution 80 (13)
5.1 Self-reciprocal Linear Substitutions 82 (1)
5.2 Homogeneous Linear Substitutions 82 (4)
5.3 Binary Linear Substitutions 86 (1)
5.4 General Linear Substitutions 86 (1)
5.5 Decomposed Linear Substitutions 87 (3)
5.6 Decimated Alphabets 90 (1)
5.7 Linear Substitutions with Decimal and 91 (2)
Binary Numbers
6 Encryption Steps: Transposition 93 (13)
6.1 Simplest Methods 93 (5)
6.2 Columnar Transpositions 98 (4)
6.3 Anagrams 102(4)
7 Polyalphabetic Encryption: Families of 106(33)
Alphabets
7.1 Iterated Substitutions 106(1)
7.2 Cyclically Shifted and Rotated 107(3)
Alphabets
7.3 Rotor Crypto Machines 110(17)
7.4 Shifted Standard Alphabets: Vigen?e 127(4)
and Beaufort
7.5 Unrelated Alphabets 131(8)
8 Polyalphabetic Encryption: Keys 139(30)
8.1 Early Methods with Periodic Keys 139(2)
8.2 ‘Double Key’ 141(1)
8.3 Vernam Encryption 142(2)
8.4 Quasi-nonperiodic Keys 144(1)
8.5 Machines that Generate Their Own Key 145(11)
Sequences
8.6 Off-Line Forming of Key Sequences 156(2)
8.7 Nonperiodic Keys 158(3)
8.8 Individual, One-Time Keys 161(4)
8.9 Key Negotiation and Key Management 165(4)
9 Composition of Classes of Methods 169(24)
9.1 Group Property 169(2)
9.2 Superencryption 171(2)
9.3 Similarity of Encryption Methods 173(1)
9.4 Shannon’s ‘Pastry Dough Mixing’ 174(6)
9.5 Confusion and Diffusion by 180(4)
Arithmetical Operations
9.6 DES and IDEA? 184(9)
10 Open Encryption Key Systems 193(18)
10.1 Symmetric and Asymmetric Encryption 194(2)
Methods
10.2 One-Way Functions 196(7)
10.3 RSA Method 203(2)
10.4 Cryptanalytic Attack upon RSA 205(3)
10.5 Secrecy Versus Authentication 208(2)
10.6 Security of Public Key Systems 210(1)
11 Encryption Security 211(22)
11.1 Cryptographic Faults 211(9)
11.2 Maxims of Cryptology 220(5)
11.3 Shannon’s Yardsticks 225(1)
11.4 Cryptology and Hunan Rights 226(7)
Part II: Cryptanalysis The Machinery 233(254)
12 Exhausting Combinatorial Complexity 237(15)
12.1 Monoalphabetic Simple Encryptions 238(1)
12.2 Monoalphabetic Polygraphic 239(2)
Encryptions
12.3 Polyalphabetic Encryptions 241(3)
12.4 General Remarks on Combinatorial 244(1)
Complexity
12.5 Cryptanalysis by Exhaustion 244(2)
12.6 Unicity Distance 246(2)
12.7 Practical Execution of Exhaustion 248(3)
12.8 Mechanizing the Exhaustion 251(1)
13 Anatomy of Language: Patterns 252(16)
13.1 Invariance of Repetition Patterns 252(2)
13.2 Exclusion of Encryption Methods 254(1)
13.3 Pattern Finding 255(4)
13.4 Finding of Polygraphic Patterns 259(1)
13.5 The Method of the Probable Word 259(5)
13.6 Automatic Exhaustion of the 264(2)
Instantiations of a Pattern
13.7 Pangrams 266(2)
14 Polyalphabetic Case: Probable Words 268(22)
14.1 Non-Coincidence Exhaustion of 268(3)
Probable Word Position
14.2 Binary Non-Coincidence Exhaustion 271(1)
14.3 The De Viaris Attack 272(8)
14.4 Zig-Zag Exhaustion of Probable Word 280(1)
Position
14.5 The Method of Isomorphs 281(6)
14.6 A clever brute force method: EINSing 287(1)
14.7 Covert Plaintext-Cryptotext 288(2)
Compromise
15 Anatomy of Language: Frequencies 290(30)
15.1 Exclusion of Encryption Methods 290(1)
15.2 Invariance of Partitions 291(2)
15.3 Intuitive Method: Frequency Profile 293(1)
15.4 Frequency Ordering 294(3)
15.5 Cliques and Matching of Partitions 297(6)
15.6 Optimal Matching 303(2)
15.7 Frequency of Multigrams 305(5)
15.8 The Combined Method of Frequency 310(6)
Matching
15.9 Frequency Matching for Polygraphic 316(1)
Substitutions
15.10 Free-Style Methods 317(1)
15.11 Unicity Distance Revisited 318(2)
16 Kappa and Chi 320(10)
16.1 Definition and Invariance of Kappa 320(3)
16.2 Definition and Invariance of Chi 323(2)
16.3 The Kappa-Chi Theorem 325(1)
16.4 The Kappa-Phi Theorem 326(2)
16.5 Symmetric Functions of Character 328(2)
Frequencies
17 Periodicity Examination 330(20)
17.1 The Kappa Test of Friedman 331(1)
17.2 Kappa Test for Multigrams 332(1)
17.3 Cryptanalysis by Machines: Searching 333(6)
for a period
17.4 Kasiski Examination 339(6)
17.5 Building a Depth and Phi Test of 345(3)
Kullback
17.6 Estimating the Period Length 348(2)
18 Alignment of Accompanying Alphabets 350(25)
18.1 Matching the Profile 350(4)
18.2 Aligning Against Known Alphabet 354(4)
18.3 Chi Test: Mutual Alignment of 358(5)
Accompanying Alphabets
18.4 Reconstruction of the Primary 363(2)
Alphabet
18.5 Kerckhoffs’ Symmetry of Position 365(5)
18.6 Stripping off Superencryption: 370(3)
Difference Method
18.7 Decryption of Code 373(1)
18.8 Reconstruction of the Password 373(2)
19 Compromises 375(84)
19.1 Kerckhoffs’ Superimposition 375(2)
19.2 Superimposition for Encryptions with 377(24)
a Key Group
19.3 COLOSSUS 401(11)
19.4 Adjustment ‘in depth’ of Messages 412(7)
19.5 Crypt otext-Cryptot ext Compromises 419(12)
19.6 Cryptotext-Cryptotext Compromise: 431(17)
ENIGMA Indicator Doubling
19.7 Plaintext-Cryptotext Compromise: 448(11)
Feedback Cycle
20 Linear Basis Analysis 459(5)
20.1 Reduction of Linear Polygraphic 459(1)
Substitutions
20.2 Reconstruction of the Key 460(1)
20.3 Reconstruction of a Linear Shift 461(3)
Register
21 Anagramming 464(6)
21.1 Transposition 464(3)
21.2 Double Columnar Transposition 467(1)
21.3 Multiple Anagramming 467(3)
22 Concluding Remarks 470(17)
22.1 Success in Breaking 471(5)
22.2 Mode of Operation of the 476(6)
Unauthorized Decryptor
22.3 Illusory Security 482(2)
22.4 Importance of Cryptology 484(3)
Appendix: Axiomatic Information Theory 487(10)
Bibliography 497(4)
Index 501(24)
Photo Credits 525
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