Preface. 10
1. How can I break an encrypted message? And other introductory questions. 13
- What is this book about?
- Which technical terms do I need to know?
- How can I break an encrypted text?
- How do I know what kind of encryption I am dealing with?
- I have found an encrypted text in the attic; can you decipher it for me?
- I have encrypted a text myself, can you break it?
- I have invented a new encryption method; can you take a look at it?
- I have solved a famous unsolved cryptogram, what shall I do?
- What tools do I need for codebreaking?
- How can I encrypt my files and emails?
- I have a comment on this book, what shall I do?
- Who contributed to this book? (Acknowledgements). 22
2. The Caesar cipher
- How the Caesar cipher works
- How to detect a Caesar cipher
- How to break a Caesar cipher
- Success stories
- A prison inmate cipher
- A spy’s encrypted sheet
- An encrypted journal from the movie The Prestige
- Challenges
- Herbert Yardley’s first challenge
- A series of newspaper advertisements from 1900
. 25
3. Simple substitution ciphers. 33
- How simple substitution ciphers work
- How to detect a simple substitution cipher
- Example of a cipher that is not a simple substitution cipher
- Index of coincidence technique
- How to break a simple substitution cipher
- Frequency analysis
- Guessing frequent words
- Guessing words with unusual letter patterns
- Success stories
- How Gary Klivans broke a prison inmate code
- How Kent Boklan broke encrypted diary entries from the Civil War
- Beatrix Potter’s diary
- Challenges
- Prison code
- A postcard
- Another postcard
- Friedmans’ wedding centennial nickel
- An Aristocrat from the ACA
- Unsolved cryptograms
- An encrypted newspaper ad from 1888
- The Zodiac Celebrity Cypher
. 34
4. Simple substitution ciphers without spaces between words: Patristocrats. 51
- How a Patristocrat, a simple substitution cipher without spaces, works
- How to detect a Patristocrat
- How to break a Patristocrat
- Frequency analysis and word guessing
- Word guessing
- Success stories
- A prison message
- The Cheltenham Number Stone
- Challenges
- Rudyard Kipling’s encrypted message
- NSA’s second Monday challenge
- Unsolved cryptograms
- The Dorabella cryptogram
- The Chinese gold bars mystery
- James Hampton’s notebook
. 51
5. Simple substitution ciphers in non-English languages. 63
- Detecting the language used
- How to break a non-English simple substitution cipher
- Frequency analysis and word-guessing
- Word pattern guessing
- Success stories
- How André Langie broke a pigpen cipher (Spanish)
- The La Buse cryptogram (French)
- A postcard with a love message (German)
- A Mafia message (Italian)
- Challenges
- An encrypted postcard
- The third NSA Monday Challenge
- Christlieb Funk’s challenge cryptogram
- Unsolved cryptograms
- The Voynich Manuscript
- Cigarette case cryptogram
- NSA’s fourth Monday Challenge
- Moustier altar inscriptions
. 64
6. Homophonic ciphers. 80
- How homophonic ciphers work
- How to detect a homophonic cipher
- How to break a homophonic cipher
- Success stories
- The first Zodiac message (Z408)
- Ferdinand III’s letters
- A postcard from Hawaii
- Challenges
- A message to the Zodiac Killer
- Edgar Allan Poe’s second challenge
- Unsolved cryptograms
- Beale Papers #1 & #3
- The Zodiac Killer’s second message (Z340)
- The Zodiac Killer’s third message (Z13)
- The Zodiac Killer’s fourth message (Z32)
- Scorpion cryptograms
- Henry Debosnys’ messages
. 82
7. Codes and nomenclators. 99
- Codes
- The difference between codes and ciphers
- Nomenclators
- Terminology
- History of codes and nomenclators
- Super-encryption of codes and nomenclators
- How to detect a code or nomenclator
- How to break a code or nomenclator
- Finding the nomenclator table or codebook
- Exploiting weaknesses of codes and nomenclators
- Solving codes and nomenclators with cribs
- Success stories
- A telegram sent to Tel Aviv
- Mary, Queen of Scots
- Lord Franklin search expedition
- The Japanese JN-25 code
- Challenges
- Mount Everest telegram
- Unsolved cryptograms
- Silk dress cryptogram
- The train station robbery cryptogram
- Pollaky’s newspaper advertisement
- Lord Manchester’s Letter
. 100
8. Polyalphabetic ciphers. 125
- How a polyalphabetic cipher works
- Vigenère cipher
- Polyalphabetic ciphers
- One-time pad
- How to detect a polyalphabetic cipher
- How to break a polyalphabetic cipher
- Word guessing
- Checking for repeating patterns (Kasiski’s method)
- Using the index of coincidence
- Dictionary attack
- Tobias Schrödel’s method
- Other Vigenère breaking methods
- How to break a one-time pad
- Success stories
- Diana Dors’ message
- Kryptos 1 and 2
- The Cyrillic Projector
- Thouless’s second cryptogram from the crypt
- The Smithy Code
- Challenges
- Schooling challenge
- A German radio message from the Second World War
- Unsolved cryptograms
- Wood’s cryptogram from the crypt
. 125
9. Complete columnar transposition ciphers. 149
- How complete columnar transposition ciphers work
- How to detect a complete columnar transposition
- How to break a complete columnar transposition cipher
- The arrange-and-read method
- Vowel frequencies and multiple anagramming
- Success stories
- Donald Hill’s diary
- The Pablo Waberski spy case
- Challenges
- Love in Code
- The Friedmans’ love messages
- Agony Column
- Yardley’s 11th ciphergram
- Edgar Allan Poe’s first challenge
- IRA messages
. 150
10. Incomplete columnar transposition ciphers 167
- How an incomplete columnar transposition works
- How to detect an incomplete columnar transposition
- How to break an incomplete columnar transposition
- Success stories
- Kryptos – K3
- Antonio Marzi’s radio messages
- Challenges
- IRA
- Double Columnar Transposition Reloaded
- Unsolved cryptograms
- Catokwacopa
. 167
11. Turning grille transposition ciphers. 185
- How turning grille encryption works
- How to detect a turning grille encryption
- How to break a turning grille encryption
- Success stories
- Paolo Bonavoglia’s solution of a turning grille
- André Langie’s solution of a turning grille
- Karl de Leeuw’s solution of a turning grille
- The Mathias Sandorf cryptogram
- Challenges
- The Friedman’s Christmas card
- Jew-Lee and Bill’s Cryptocablegram
- MysteryTwister C3 challenge
- Kerckhoffs’ cryptogram
. 186
12. Digraph substitution. 205
- How a digraph substitution works
- General case
- The Playfair cipher
- How to detect a digraph substitution
- General case
- Detection of a Playfair cipher
- How to break a digraph substitution
- Frequency analysis
- Dictionary attack
- Manual attack on the Playfair cipher
- Success stories
- Thouless’s first message
- Thouless’s third message
- Challenges
- National Treasure: Book of Secrets
- Unsolved cryptograms
- World record digraph challenge
- World record Playfair challenge
. 205
13. Abbreviation ciphers 229
- How abbreviation ciphers work
- How to detect an abbreviation cipher
- How to break an abbreviation cipher
- Success stories
- Emil Snyder’s booklet
- Challenges
- A birthday card
- Unsolved cryptograms
- The Tamam Shud mystery
- Two unsolved postcards
. 229
14. Dictionary codes and book ciphers. 238
- How dictionary codes and book ciphers work
- How to detect a dictionary code or book cipher
- How to break a dictionary code or book cipher
- Identifying the book or dictionary
- Reconstructing the dictionary
- Treating a book cipher like a simple substitution cipher
- Success stories
- The FIDES ads
- Nicolas Trist’s key book
- William Friedman and the Hindu Conspiracy
- A dictionary code message sent to Robert E. Lee
- Challenges
- Dan Brown’s book cipher challenge
- Dictionary code challenge
- Unsolved cryptograms
- Two encrypted newspaper advertisements from 1873
. 239
15. Additional encryption methods. 252
- Cipher tools. 252
- Voice encryption. 253
- Code talking. 254
- Shorthand (stenography) 255
- Hidden messages (steganography)
- Success story: How Elonka found a hidden message on a tombstone. 260
- Success story: Deciphering Steganographia. 262
- Success story: Mysterious Stranger message
- Challenge: Another steganographic message by the Friedmans
- Cipher machines. 268
16. Solving ciphers with hill climbing. 273
- Solving simple substitution ciphers with hill climbing
- Success story: Bart Wenmecker’s solution of the Baring-Gould cryptogram
- Success story: Florida murder case cryptogram
- Solving a homophonic cipher with hill climbing
- Success story: Dhavare, Low, and Stamp’s Zodiac Killer solutions
- Solving a Vigenère cipher with hill climbing
- Success story: Jim Gillogly’s solution of IRA Vigenère cryptograms
- Solving a columnar transposition with hill climbing
- Success story: Jim Gillogly’s solution of IRA transposition cryptograms
- Success story: Richard Bean’s solution of the last unsolved IRA cryptogram
- Success story: George Lasry’s solution of the double columnar transposition challenge
- Solving a turning grille cipher with hill climbing
- Success story: Bart Wenmeckers’ solution of a turning grille cryptogram
- Success story: Armin Krauß’s solution of a turning grille challenge
- Solving a general digraph substitution with hill climbing
- Success story: Digraph challenges
- Solving a Playfair cipher with hill climbing
- Success story: Dan Girard’s solution of the Cheltenham Letter Stone
- Success story: Playfair challenges
- Solving machine ciphers with hill climbing
- Success story: Breaking the Enigma
. 274
17. What next?. 297
- More unsolved cryptograms
- The fourth Kryptos message (K4)
- The Rubin cryptogram
- Ricky McCormick’s encrypted notes
- The World War II carrier pigeon message
- Even more unsolved cryptograms
- Codebreaking tools
- Other books about codebreaking (Recommended reading)
- Websites about codebreaking (links)
- Journals and newsletters
- Events
. 297
Appendix A: Kryptos
. 311
Appendix B: Useful language statistics. 313
- Letter frequencies
- Most frequent digraphs
- Most frequent doubled letters
- Most frequent trigraphs
- Most frequent words
- Average word lengths in a text
- Index of coincidence
. 313
Appendix C: Glossary. 318
Appendix D: Figure sources. 322
Index. 332