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Elementary cryptanalysis

Chapter 34: INDEX
By Helen Fouché Gaines
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About This Book

A practical instructional treatment of classical cryptanalysis that concentrates on techniques for analyzing and solving encrypted messages rather than codes or chemical and mechanical devices. It surveys concealment methods, transposition and geometrical systems, irregular and columnar types, single- and polyalphabetic substitution (including Vigenère, Gronsfeld, Beaufort, and Playfair), periodic-cipher analysis such as the Kasiski method, auto-encipherment, and approaches for attacking unknown ciphers. Each topic is presented with explanatory discussion, worked examples, and practice cryptograms, while appendices provide frequency tables, digram/trigram data, common-word lists, charts, and a bibliography to support statistical and linguistic decryptment methods.


REA        95     INE      73     ORE       65     ART       58
WIT 93WHI 71BUT 64NTE 58
ONS 92OVE 71OUT 63RAT 58
ESS 90TIN 71URE 63TUR 58
AVE 84AST 70STR 62ICA 57
PER 84DER 70TIC 62ICH 57
ECT 83OUS 70AME 61NDE 57
ONE 83ROM 70COM 61PRE 57
UND 83VEN 70OUR 61ENC 56
INT 80ARD 69WER 61HAS 56
ANT 79EAR 69OME 60WHE 55
HOU 77DIN 68EEN 59WIL 55
MEN 76STI 68LAR 59ERA 54
WAS 76NOT 67LES 59LIN 54
OUN 75ORT 67SAN 59TRA 54
PRO 75THO 66STE 59
STA 75DAY 65ANY 58

ENGLISH DIGRAMS

The one hundred and nine most frequent English digrams, compiled from a count of 20,000 trigrams by Fletcher Pratt, in “Secret and Urgent,” supposed not to include overlaps between words, and 5,000 by Frank R. Fraprie, including overlaps.

 

TH    1582     RO     275     WI     188     SA     146     CT     111
IN 784LI 273HO 184NI 142TU 108
ER 667RI 271TR 183RT 142DA 107
RE 625IO 270BE 181NA 141AM 104
AN 542LE 263CE 177OL 141CI 104
HE 542ND 263WH 177EV 131SU 102
AR 511MA 260LL 176IE 129BL 101
EN 511SE 259FI 175MI 128OF 101
TI 510AL 246NO 175NG 128BU 100
TE 492IC 244TO 175PL 128
AT 440FO 239PE 174IV 127
ON 420IL 232AS 172PO 125
HA 420NE 232WA 171CH 122
OU 361LA 229UR 169EI 122
IT 356TA 225LO 166AD 120
ES 343EL 216PA 165SS 120
ST 340ME 216US 165IL 118
OR 339EC 214MO 164OS 117
NT 337IS 211OM 163UL 115
HI 330DI 210AI 162EM 114
EA 321SI 210PR 161NS 113
VE 321CA 202WE 158OT 113
CO 296UN 201AC 152GE 112
DE 275UT 189EE 148IR 112
RA 275NC 188ET 146AV 111

INDEX

Amateurs, devices proposed by,
132
,
140
,
152

“Amsco” transposition cipher,
51

Anagramming,
22
,
29
,
45
-
50

Anagramming, multiple,
32
,
56
-
68

“Aristocrats,”
69
,
72
,
88

Auto-encipherment,
146
-
158


Bacon’s biliteral cipher,
6

Basic cipher alphabet,
164

Bassières processes for autokey,
147
-
151

Beaufort ciphers,
121

“Bifid” substitution,
210

Book cipher,
106


“Caesar” alphabets,
69
,
71
,
100
,
108
, 118,
130

Characteristics of systems,
53
,
100
,
103
, 105,
130
,
153
,
168
,
201
-
203
,
213
-
214

“Checkerboard” alphabets,
102
,
104
,
164
,
209

Cipher, meaning of,
1

Cipher alphabets,
69
,
130
,
159
,
172
,
185

Cipher disks,
108
,
111

Cipher disks, special application of,
192

Classification of ciphers,
1

Classification of substitutions,
68

Code,
1
,
106

Collon systems,
209

Columnar transposition,
11
,
17
,
23
,
37
-
52

Columnar transposition, double,
54

“Columns” in autokeyed ciphers,
146

Combination block,
44

Combination cipher,
1
,
4
,
6
,
68
,
207
,
209
,
213
,
216

Complements, complementary alphabets,
123

Complete-unit transposition,
9

Concealment cipher, meaning of,
1

Concealment ciphers,
4
-
8

Consonant-line method for simple substitution,
88

Contact count,
74
,
77
,
83
,
173

Conventional writing,
4

“Crypt,”
72
,
91

Cryptanalysis, meaning of,
3

Cryptogram, meaning of,
1

Cryptographic security,
2

Cycle (see
period
or
unit
)

Cyclical encipherment,
186
,
200


Deciphering alphabet (or key),
71
,
104

Decipherment, meaning of,
1

Decoding, meaning of,
2

Decrypt, meaning of,
1

Definitions, miscellaneous,
1
,
68
-
70

Dictionary cipher,
106

Digram, meaning of,
1

Digram count,
83

Digram-solution method for simple substitution,
83

Digram tests,
45
,
46
,
47
,
50

Dissimulated writing,
4

Double-key substitution, meaning of,
68

Double Myszkowsky transposition,
60

Double substitutions,
155
,
164
,
193

Double transpositions,
18
,
54


Empty, or negative, words,
76

Encipherment, meaning of,
1

Encoding, meaning of,
2

“Entry,”
74

Equivalent slide (or alphabet),
169
,
180


Factoring, in transpositions,
12
,
42

Factoring of intervals to find a period,
128
,
132

“Force Method,”
90