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188 CHAPTER 9. DIGRAPHIC CIPHERS On Saturday morning, August 7th, Even received news from a native that the crew had been found and moved to Gross Island. He sent the following message: XELWA OHWUW YZMWI HOMNE OBTFW MSSPI AJLUO EAONG OOFCM FEXTT CWCFZ YIPTF EOBHM WEMOC SAWCZ SNYNW MGXEL HEZCU FNZYL NSBTB DANFK OPEWM SSHBK GCWFV EKMUE The key was Physical Examination. Decipher the message. (c) Another message reused the key Physical Examination, and began XYAWO GAOOA GPEMO HPQCW IPNLG RPIXL TXLOA NNYCS YXBOY MNBIN YOBTY QYNAI Later messages explained the rescue arrangements. The combination of messages could have been easily solved in an hour by any moderately experienced cryptanalyst. If solved, the Japanese could have gotten both the shipwrecked crew and the rescue force. For whatever reason, there was no enemy action taken, and Lt. Kennedy was rescued and went on to become President. 23. H.F. Gaines [page 199] proposed a cipher that uses the Saint Cyr Slide to implement a digraphic cipher, calling it, logically enough “Slidefair”. Start by setting the keyletter under a, as usual. To encipher a pair of letter, find the first letter in the plaintext strip and the second in the cipherstrip. Replace them by other corners of the rectangle then formed, first letter from the plainstrip and second from the cipherstrip. If the letters happen to occur as a horizontal pair, replace them by the letters directly to their right. Her example used the keyword HERCULES and produced the ciphertext XZ ZR RU KC TI HO KX US MZ NI JU KO TI PO SC MW PR PM XY RW GZ AT What was the plaintext
Chapter 10 Transposition Ciphers In one word, the transposition methods give a nice mess [salade] of cleartext letters. Etienne Bazeries So far each of the methods of ciphering we’ve studied have been substitution methods. They obtain their secrecy by hiding the meaning of the letter. In this chapter we turn to transposition ciphers, ciphers which obtain their secrecy by hiding the location of the letter. We start with a couple of simple classics. 10.1 Route Ciphers Route ciphers are also called rail fence ciphers, for an obvious reason. Examples: Decipher the route ciphers. (1) Decipher AEICL BLNON. a e i c l b l n o n (2) Decipher TEIEP NDSR. (3) Decipher OBNN LAIECL DLO. (Hint: three rows.) (4) Decipher ILE ALPITR RST. (5) Decipher ILVGI IOIAE ITSRN MANHM NG. 1 (Try three rows.) ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ 1 (2) Two rows, read backwards: president, (3) Old Abe Lincoln, (4) rail splitter, (5) I am leaving this morning – from [HITT, page 28]. 189
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Cryptology: An Historical Introduct
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Contents List of Figures 8 1 Caesar
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CONTENTS 5 9 Digraphic Ciphers 167
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List of Figures 1.1 Saint Cyr Slide
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Chapter 1 Caesar Ciphers There are
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11 Examples: Encipher or decipher t
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1.1. SAINT CYR SLIDE 13 paper turne
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1.3. FREQUENCY ANALYSIS 15 PX PBEE
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1.3. FREQUENCY ANALYSIS 17 A bit mo
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1.3. FREQUENCY ANALYSIS 19 Examples
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1.4. LINQUIST’S METHOD 21 the cip
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1.7. EXERCISES 23 12. What is the m
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1.7. EXERCISES 25 (d) VTXLTKBTG LXV
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1.7. EXERCISES 27 (d) IKSUT JKIOT K
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Chapter 2 Cryptologic Terms Cryptog
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Chapter 3 The Introduction of Numbe
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3.1. THE REMAINDER OPERATOR 33 Exam
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3.1. THE REMAINDER OPERATOR 35 Perf
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3.1. THE REMAINDER OPERATOR 37 As a
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3.2. MODULAR ARITHMETIC 39 While %
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3.3. DECIMATION CIPHERS 41 previous
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3.4. DECIPHERING DECIMATION CIPHERS
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3.6. KOBLITZ’S KID-RSA AND PUBLIC
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3.6. KOBLITZ’S KID-RSA AND PUBLIC
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3.9. EXERCISES 49 8. How do we enci
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3.9. EXERCISES 51 (c) Encipher 54 4
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3.9. EXERCISES 53 (b) Encipher secr
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Chapter 4 The Euclidean Algorithm I
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4.2. GCD’S AND THE EUCLIDEAN ALGO
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4.3. MULTIPLICATIVE INVERSES 59 (2)
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4.3. MULTIPLICATIVE INVERSES 61 (2)
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4.4. DECIPHERING DECIMATION AND LIN
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4.5. BREAKING DECIMATION AND LINEAR
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4.6. SUMMARY 67 To put it more blun
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4.8. EXERCISES 69 5. Here we work w
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Chapter 5 Monoalphabetic Ciphers He
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5.2. KEYWORD MIXED CIPHERS 73 Examp
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5.4. INTERRUPTED KEYWORD CIPHERS 75
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5.6. BASIC LETTER CHARACTERISTICS 7
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5.7. ARISTOCRATS 79 the 69971 or 42
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5.9. TOPICS AND TECHNIQUES 81 5.9 T
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5.10. EXERCISES 83 (h) DYVTP KKIQ.
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5.10. EXERCISES 85 13. Ciphers in w
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5.10. EXERCISES 87 17. General Pier
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Chapter 6 Decrypting Monoalphabetic
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6.2. DECRYPTING MONOALPHABETIC CIPH
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6.3. SUKHOTIN’S METHOD FOR FINDIN
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6.4. FINAL MONOALPHABETIC TRICKS 99
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6.5. SUMMARY 101 our ciphertext muc
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6.7. EXERCISES 103 Frequency count:
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6.7. EXERCISES 105 53++!305))6*;482
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6.7. EXERCISES 107 93 93 82 48 39 6
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Chapter 7 Vigenère Ciphers It was
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7.2. TRITHEMIUS, THE FATHER OF BIBL
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7.3. BELASO, THE UNKNOWN AND PORTA,
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7.4. VIGENÈRE CIPHERS 115 to encip
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7.6. HOW TO BREAK VIGENÈRE CIPHERS
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7.6. HOW TO BREAK VIGENÈRE CIPHERS
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7.7. THE KASISKI TEST 121 Kasiski
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7.8. SUMMARY 123 Repetition Start P
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7.10. EXERCISES 125 2. Little Miss
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7.10. EXERCISES 127 to Gen. E. K. S
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7.10. EXERCISES 129 MEJMY JKXCD LCN
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7.10. EXERCISES 131 22. (a) Use Kas
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7.10. EXERCISES 133 (a) Construct a
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Chapter 8 Polyalphabetic Ciphers Th
Page 137 and 138: 8.1. COINCIDENCES 137 (being born o
Page 139 and 140: 8.2. THE MEASURE OF ROUGHNESS 139 I
Page 141 and 142: 8.2. THE MEASURE OF ROUGHNESS 141 P
Page 143 and 144: 8.3. THE FRIEDMAN TEST 143 The Frie
Page 145 and 146: 8.4. MULTIPLE ENCIPHERINGS 145 Bein
Page 147 and 148: 8.4. MULTIPLE ENCIPHERINGS 147 Just
Page 149 and 150: 8.5. VIGENÈRE’S AUTO KEY CIPHER
Page 151 and 152: 8.5. VIGENÈRE’S AUTO KEY CIPHER
Page 153 and 154: 8.6. PERFECT SECRECY 153 invent now
Page 155 and 156: 8.8. TERMS AND TOPICS 155 multiple
Page 157 and 158: 8.9. EXERCISES 157 6. As is this on
Page 159 and 160: 8.9. EXERCISES 159 13. It has been
Page 161 and 162: 8.9. EXERCISES 161 This is Equation
Page 163 and 164: 8.9. EXERCISES 163 A: AB CDE FGH I
Page 165 and 166: 8.9. EXERCISES 165 26. Decipher SVQ
Page 167 and 168: Chapter 9 Digraphic Ciphers Althoug
Page 169 and 170: 9.1. POLYGRAPHIC CIPHERS 169 f a g
Page 171 and 172: 9.2. HILL CIPHERS 171 th 2.96 es 1.
Page 173 and 174: 9.2. HILL CIPHERS 173 We will be us
Page 175 and 176: 9.3. RECOGNIZING AND BREAKING POLYG
Page 177 and 178: 9.4. PLAYFAIR 177 Playfair Ciphers:
Page 179 and 180: 9.5. SUMMARY 179 9.5 Summary Polygr
Page 181 and 182: 9.7. EXERCISES 181 (b) The use of
Page 183 and 184: 9.7. EXERCISES 183 10. Just as we c
Page 185 and 186: 9.7. EXERCISES 185 (d) (For those(
Page 187: 9.7. EXERCISES 187 The rules that W
Page 191 and 192: 10.3. TURNING GRILLES 191 1 2 3 7 4
Page 193 and 194: 10.4. COLUMNAR TRANSPOSITION 193 co
Page 195 and 196: 10.5. TRANSPOSITION VS. SUBSTITUTIO
Page 197 and 198: 10.6. LETTER CONNECTIONS 197 F 2 G
Page 199 and 200: 10.7. BREAKING THE COLUMNAR TRANSPO
Page 201 and 202: 10.8. DOUBLE TRANSPOSITION 201 Sinc
Page 203 and 204: 10.9. TRANSPOSITION DURING THE CIVI
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Page 207 and 208: 10.10. THE BATTLE OF THE CIVIL WAR
Page 209 and 210: 10.13. EXERCISES 209 14. What is a
Page 211 and 212: 10.13. EXERCISES 211 and the second
Page 213 and 214: 10.13. EXERCISES 213 evening Adam h
Page 215 and 216: 10.13. EXERCISES 215 Several codewo
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Page 219 and 220: Chapter 11 Knapsack Ciphers Merkle
Page 221 and 222: 11.3. AN EASY KNAPSACK PROBLEM 221
Page 223 and 224: 11.4. THE KNAPSACK CIPHER SYSTEM 22
Page 225 and 226: 11.4. THE KNAPSACK CIPHER SYSTEM 22
Page 227 and 228: 11.5. PUBLIC KEY CIPHER 227 Even wi
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Page 231 and 232: Chapter 12 RSA Take two large prime
Page 233 and 234: 12.1. FERMAT’S THEOREM 233 Exampl
Page 235 and 236: 12.3. COMPLICATION II: A SUBSTANTIA
Page 237 and 238: 12.3. COMPLICATION II: A SUBSTANTIA
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12.5. COMPLICATION IV: THE LAST ONE
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12.6. PUTTING IT ALL TOGETHER 241 1
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12.8. RSA 243 The RSA Algorithm Set
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12.9. RSA AND PUBLIC KEYS 245 There
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12.10. HOW TO BREAK RSA 247 had to
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12.12. SUMMARY 249 cannot read the
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12.14. EXERCISES 251 6. What is a
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12.14. EXERCISES 253 Bob is going t
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Bibliography [Antonucci] Michael An
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BIBLIOGRAPHY 257 [Shamir] [SRA] A.
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