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156 CHAPTER 8. POLYALPHABETIC CIPHERS 13. What is the key for an Auto Key cipher 14. Give a strength and a weakness of the Auto Key Cipher. 15. What is “Perfect Secrecy” 16. How does the One-Time Pad work 17. Give a strength and a weakness of the One-Time Pad system. 8.9 Exercises For Problems 1 through 6, do a frequency count and use it to compute Φ. Use this value to estimate the keylength. Try to find a couple of repetitions in the ciphertext that seem to validate your keylength guess. Then decipher the message. 1. COMUB XWYKU OXTIY UBXNQ AFLXC SMIYR BLXUI UFJKF ZXSLX EUKFN ASYXU BTUNA FSUFH HUFTC IKJIN TNHXL BUYTO XKFUW FNABN MIYRC YXJGI PMLJV EFNHE CLDSI IYKBH WJHLP GXDUL FMMIU MUBXZ VXFQB UBHVN LVMIJ NBPH 2. ZYIBX YKXHT ZTENU KVBPX IKIDB YKLAM ZYIDX MIIEH LJICN XZXYU KXVET ZVRON MYXOW KCEYL UCYTB UEFYM NVINX SPJOK YLGHT RVRGM NFJTB SVXHT ZNLEG ZYISH RLXIH TZWFB TRPLR XVECA KUXHX OEJOK SRXIH TKLUL USXAB TVHHT YCSSM GCPIM YMELN K 3. (a) QZIQU DTKUT IWCUG LJZIU MSVHO KIGNZ IDCEW KIMPG VWRHP WVWIS POIOE QSDIW NWVWI STSYS VWQAG HUDMN YLLHH MQEYJ SIFWX WYJWX HVIUY SGKEW CLMLS EYSWV GSPOU KTRMK MEFW (b) What is the meaning of the quote 4. IKUQN VOCSJ MPYKA BIJFG NXGGS YOYRV RSLCK ZEKIC EEMQY JFCMF RCNTU NHVDK EEFCN MUQIF ZCDWA PADAK EEFYR PQVCY MLGVA DLVFR EIEZE KICEE ECVVD YLZEM LRFCD GQMPC QYNUM KEKTM DFRAR PBROX DYPYK GNUQB TFSMV VDLTY QAOID CSGAL DVZAE SQRWV QLDZR DEIQL TRDKY TTGEW EDOIM LUEXG MZFCD KUKE 5. This one is a bit harder: MOVBA NZLIB GFLTR DWJBW YEJZU BKIXP ZVKHG SWVWA XLPDF RVZBB JUSSE FWOMU WVLTL OXRVY LOXJF NKLJB VNULL VWTZP LPEGW UNPKY OHLVT CSZBV EADSR WRIFM NSKHW VPUVR KVYAY EVLML TTWKV PGHWY LZFMW ABTVS LOKHJ HWKFL KHGBZ OKHWM TBCTD HRPET ZLBYF WFZMB GIVPM F
8.9. EXERCISES 157 6. As is this one: KHVBH FXPSP NMJET MGXWF RLIEN OGMOO TRHRV ADUJH KSOGN WXKSU IFYYT XVVRR HTSTF HYNZF KZVCS FJGAC UIPIG GBAML FCZGN LEWVC HWXVV UHNWX KLCHV OUJCU HRVLV UWWER HXWGQ ENWPA GFRRH KLGVN WXJSH HBXFR VISNW ODFGF BOCEH KJVMO RPUWG LILPF PRLID TTCZR MVHCH RJWYI PUNPY DIPHV WQYME VBWYF VCBBC BVVQT GQYDX QCXYU IX 7. Encipher or decipher the following texts using a Vigenére cipher with two keywords. (a) Encipher Peter Piper picked a peck using the keywords JACK and SPRATT. (b) Decipher FDUAP XNQHJ LCWOI UIOHF BEUDN C using the keywords LIZARD and CRAWL. (c) Encipher I need to laugh, and when the sun is out using the keywords Sun and shine. (d) Decipher RJQMU FJRQV HIRBS OIMEO ELUIJ PAAZ using keywords Good and day. 8. Matteo Argenti used the keyword Key PIETRO and a slightly mixed alphabet to make a Vigenère cipher: cipher plain1 plain2 plain3 plain4 plain5 plain6 HI LMNOPRSTABCDE FGU p r s t u a b c d e f g h i l m n o i l m n o p r s t u a b c d e f g h e f g h i l mnop r s t u a b c d t u a b c d e f gh i l mn o p r s r s t u a b c d e f g h i l m n o p o p r s t u a b c d e f g h i l mn To encipher, find the first letter of plaintext in the first plaintext alphabet, and replace it by the ciphertext letter above it. The second plaintext alphabet is used for the second letter, the third for the third, etc. For example peter becomes HECPH. Decipher LHUAP AHEAN SLMNG TSUUM BPAOT PEBNC NEALP HGSAE MAGEC ANUD. 9. If we are using a double Vigenère, does it matter in which order we use the keywords Explain. 10. The “Double Vigenère” we discussed in the chapter used two keywords to encipher a message twice. A different and better way to do this is to use the first key to mix the cipheralphabet and the second key as a Vigenère keyword using the newly mixed cipheralphabet (much like PIETRO was used in exercise 8.8).
Page 1 and 2:
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:
Page 105 and 106: 6.7. EXERCISES 105 53++!305))6*;482
Page 107 and 108: 6.7. EXERCISES 107 93 93 82 48 39 6
Page 109 and 110: Chapter 7 Vigenère Ciphers It was
Page 111 and 112: 7.2. TRITHEMIUS, THE FATHER OF BIBL
Page 113 and 114: 7.3. BELASO, THE UNKNOWN AND PORTA,
Page 115 and 116: 7.4. VIGENÈRE CIPHERS 115 to encip
Page 117 and 118: 7.6. HOW TO BREAK VIGENÈRE CIPHERS
Page 119 and 120: 7.6. HOW TO BREAK VIGENÈRE CIPHERS
Page 121 and 122: 7.7. THE KASISKI TEST 121 Kasiski
Page 123 and 124: 7.8. SUMMARY 123 Repetition Start P
Page 125 and 126: 7.10. EXERCISES 125 2. Little Miss
Page 127 and 128: 7.10. EXERCISES 127 to Gen. E. K. S
Page 129 and 130: 7.10. EXERCISES 129 MEJMY JKXCD LCN
Page 131 and 132: 7.10. EXERCISES 131 22. (a) Use Kas
Page 133 and 134: 7.10. EXERCISES 133 (a) Construct a
Page 135 and 136: 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: 8.8. TERMS AND TOPICS 155 multiple
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 and 188: 9.7. EXERCISES 187 The rules that W
Page 189 and 190: Chapter 10 Transposition Ciphers In
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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10.10. THE BATTLE OF THE CIVIL WAR
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10.13. EXERCISES 209 14. What is a
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10.13. EXERCISES 211 and the second
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10.13. EXERCISES 213 evening Adam h
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10.13. EXERCISES 215 Several codewo
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10.13. EXERCISES 217 4. (which is t
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Chapter 11 Knapsack Ciphers Merkle
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11.3. AN EASY KNAPSACK PROBLEM 221
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11.4. THE KNAPSACK CIPHER SYSTEM 22
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11.4. THE KNAPSACK CIPHER SYSTEM 22
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11.5. PUBLIC KEY CIPHER 227 Even wi
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11.8. EXERCISES 229 2. Given the we
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Chapter 12 RSA Take two large prime
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12.1. FERMAT’S THEOREM 233 Exampl
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12.3. COMPLICATION II: A SUBSTANTIA
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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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