If you liked Dan Brown’s Da Vinci Code—or want to solve similarly baffling cyphers yourself—this is the book for you!
A thrilling exploration of history’s most vexing codes and ciphers that uses hands-on exercises to teach you the most popular historical encryption schemes and techniques for breaking them.
Solve history’s most hidden secrets alongside expert codebreakers Elonka Dunin and Klaus Schmeh, as they guide you through the world of encrypted texts. With a focus on cracking real-world document encryptions—including some crime-based coded mysteries that remain unsolved—you’ll be introduced to the free computer software that professional cryptographers use, helping you build your skills with state-of-the art tools. You’ll also be inspired by thrilling success stories, like how the first three parts of Kryptos were broken.
Each chapter introduces you to a specific cryptanalysis technique, and presents factual examples of text encrypted using that scheme—from modern postcards to 19-century newspaper ads, war-time telegrams, notes smuggled into prisons, and even entire books written in code. Along the way, you’ll work on NSA-developed challenges, detect and break a Caesar cipher, crack an encrypted journal from the movie The Prestige, and much more.
You’ll learn:
How to crack simple substitution, polyalphabetic, and transposition ciphers
How to use free online cryptanalysis software, like CrypTool 2, to aid your analysis
How to identify clues and patterns to figure out what encryption scheme is being used
How to encrypt your own emails and secret messages
Codebreaking is the most up-to-date resource on cryptanalysis published since World War II—essential for modern forensic codebreakers, and designed to help amateurs unlock some of history’s greatest mysteries.
Author(s): Elonka Dunin, Klaus Schmeh
Edition: Expanded Edition
Publisher: No Starch Press
Year: 2023
Language: English
Pages: 686
Praise for Codebreaking
Also by Elonka Dunin and Klaus Schmeh
Title page
Copyright
Dedication
About the Authors
Preface
Chapter 1: How can I break an encrypted message? And other introductory questions
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 should I do?
What tools do I need for codebreaking?
How can I encrypt my files and email?
I have a comment on this book; what should I do?
Who contributed to this book?
Chapter 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’s 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
Chapter 3: Simple substitution ciphers
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
Performing a frequency analysis
Guessing frequent words
Guessing words with unusual letter patterns
Success stories
How Gary Klivans broke a prison inmate’s code
How Kent Boklan broke encrypted diary entries from the Civil War
Beatrix Potter’s diary
Challenges
A prison code
A postcard
Another postcard
The Friedmans’ wedding centennial nickel
An Aristocrat from the ACA
Unsolved cryptograms
An encrypted newspaper ad from 1888
The Zodiac Celebrity Cypher
The Furlong postcard
Chapter 4: Simple substitution ciphers without spaces between words: Patristocrats
How a Patristocrat, a simple substitution cipher without spaces, works
How to detect a Patristocrat
How to break a Patristocrat
Frequency analysis using digraphs
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
Chapter 5: Simple substitution ciphers in non-English languages
Detecting the language used
How to break a non-English simple substitution cipher
Frequency analysis and word guessing
Word pattern guessing
Success stories
A girl’s 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
The cigarette case cryptogram
NSA’s fourth Monday Challenge
The Moustier altar inscriptions
Chapter 6: Homophonic ciphers
How homophonic ciphers work
How to detect a homophonic cipher
How to break a homophonic cipher
Success stories
The first Zodiac message (Z408)
The Zodiac Killer’s second message (Z340)
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 and #3
The Zodiac Killer’s third message (Z13)
The Zodiac Killer’s fourth message (Z32)
The Scorpion cryptograms
Henry Debosnys’s messages
Chapter 7: Codes and nomenclators
Codes
Nomenclators
Terminology
The history of codes and nomenclators
Superencryption 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
Encrypted messages by Mary, Queen of Scots
Collinson’s search expedition
The Japanese JN-25 code
Challenges
The Mount Everest telegram
Unsolved cryptograms
The silk dress cryptogram
The train station robbery cryptogram
A Pollaky newspaper advertisement
Lord Manchester’s letter
Chapter 8: Polyalphabetic ciphers
How a polyalphabetic cipher works
Vigenère cipher
Other 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 attacks
Tobias Schrödel’s method
Other Vigenère breaking methods
How to break a one-time pad
Success stories
The Diana Dors message
Kryptos 1 and 2
The Cyrillic Projector
Thouless’s second cryptogram from the crypt
The Smithy Code
Challenges
The Schooling challenge
A German radio message from the Second World War
Unsolved cryptograms
Wood’s cryptogram from the crypt
Chapter 9: Complete columnar transposition ciphers
How complete columnar transposition ciphers work
How to detect a complete columnar transposition cipher
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
The Lampedusa message
The Friedmans’ love messages
An encrypted “agony” ad
Yardley’s eleventh ciphergram
Edgar Allan Poe’s first challenge
An IRA message
Chapter 10: Incomplete columnar transposition ciphers
How an incomplete columnar transposition cipher works
How to detect an incomplete columnar transposition cipher
How to break an incomplete columnar transposition cipher
Success stories
Kryptos K3
Antonio Marzi’s radio messages
Challenges
Yet another IRA message
The Double Columnar Transposition Reloaded challenge
Unsolved cryptograms
The Catokwacopa ad series
Chapter 11: Turning grille transposition ciphers
How turning grille encryption works
How to detect a turning grille encryption
How to break a turning grille encryption
Success stories
Paolo Bonavoglia’s turning grille solution
André Langie’s turning grille solution
Karl de Leeuw’s turning grille solution
The Mathias Sandorf cryptogram
Challenges
The Friedmans’ Christmas card
Jew-Lee and Bill’s Cryptocablegram
A MysteryTwister challenge
A Kerckhoffs cryptogram
Chapter 12: Digraph substitution
How general digraph substitution works
How the Playfair cipher works
How to detect a general digraph substitution
How to detect a Playfair cipher
How to break a digraph substitution
Frequency analysis
Dictionary attacks
Manual attacks
Success stories
Thouless’s first message
Thouless’s third message
Challenges
The cryptogram in National Treasure: Book of Secrets
Unsolved cryptograms
The world record digraph challenge
The world record Playfair challenge
Chapter 13: Abbreviation ciphers
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 Tamám Shud mystery
Two unsolved postcards
Chapter 14: Dictionary codes and book ciphers
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
Nicholas Trist’s key book
How William Friedman broke a Hindu conspiracy encryption
A dictionary code message sent to Robert E. Lee
Challenges
Dan Brown’s book cipher challenge
A dictionary code challenge
Unsolved cryptograms
Two encrypted newspaper advertisements from 1873
Chapter 15: Additional encryption methods
Cipher tools
Voice encryption
Code talking
Shorthand (stenography)
Hidden messages (steganography)
Success story: How Elonka found a hidden message on a tombstone
Success story: Deciphering Steganographia
Success story: Mysterious Stranger message
Challenge: Another steganographic message by the Friedmans
Cipher machines
Chapter 16: Solving ciphers with hill climbing
Solving simple substitution ciphers with hill climbing
Simulated annealing
Success story: Bart Wenmeckers’s solution to the Baring-Gould cryptogram
Success story: The Florida murder case cryptogram
Solving a homophonic cipher with simulated annealing
Success story: Dhavare, Low, and Stamp’s Zodiac Killer solutions
Solving a Vigenère cipher with hill climbing
Success story: Jim Gillogly’s solution to IRA Vigenère cryptograms
Solving a columnar transposition with hill climbing
Success story: Jim Gillogly’s solution to IRA transposition cryptograms
Success story: Richard Bean’s solution to 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’s solution to a turning grille cryptogram
Success story: Armin Krauss’s solution to a turning grille challenge
Solving a general digraph substitution with hill climbing
Success story: Some digraph challenges
Solving a Playfair cipher with hill climbing
Success story: Dan Girard’s solution to the Cheltenham Letter Stone
Success story: Playfair world records
Solving machine ciphers with hill climbing
Success story: Breaking original Enigma messages
Chapter 17: What next?
More unsolved cryptograms
The fourth Kryptos message (K4)
The Rubin cryptogram
Ricky McCormick’s encrypted notes
The carrier pigeon message from World War II
The encrypted NKRYPT pillars
Even more unsolved cryptograms
Codebreaking tools
Other books about codebreaking
Websites about codebreaking
Journals and newsletters
Events
Appendix A: Kryptos
Appendix B: Useful language statistics
Appendix C: Glossary
Appendix D: Morse code
Appendix E: Figure sources
Appendix F: References
Index
