book

Codebreaking

by Elonka Dunin, Klaus Schmeh

September 2023

Intermediate to advanced

488 pages

12h 49m

English

No Starch Press

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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 worksHow to detect a Caesar cipherHow to break a Caesar cipherSuccess storiesA prison inmate’s cipherA spy’s encrypted sheetAn encrypted journal from the movie The PrestigeChallengesHerbert Yardley’s first challengeA series of newspaper advertisements from 1900
Chapter 3: Simple substitution ciphers
How simple substitution ciphers workHow to detect a simple substitution cipherExample of a cipher that is not a simple substitution cipherIndex-of-coincidence techniqueHow to break a simple substitution cipherPerforming a frequency analysisGuessing frequent wordsGuessing words with unusual letter patternsSuccess storiesHow Gary Klivans broke a prison inmate’s codeHow Kent Boklan broke encrypted diary entries from the Civil WarBeatrix Potter’s diaryChallengesA prison codeA postcardAnother postcardThe Friedmans’ wedding centennial nickelAn Aristocrat from the ACAUnsolved cryptogramsAn encrypted newspaper ad from 1888The Zodiac Celebrity CypherThe Furlong postcard

Chapter 4: Simple substitution ciphers without spaces between words: Patristocrats
How a Patristocrat, a simple substitution cipher without spaces, worksHow to detect a PatristocratHow to break a PatristocratFrequency analysis using digraphsWord guessingSuccess storiesA prison messageThe Cheltenham Number StoneChallengesRudyard Kipling’s encrypted messageNSA’s second Monday ChallengeUnsolved cryptogramsThe Dorabella cryptogramThe Chinese gold bars mysteryJames Hampton’s notebook
Chapter 5: Simple substitution ciphers in non-English languages
Detecting the language usedHow to break a non-English simple substitution cipherFrequency analysis and word guessingWord pattern guessingSuccess storiesA girl’s pigpen cipher (Spanish)The La Buse cryptogram (French)A postcard with a love message (German)A Mafia message (Italian)ChallengesAn encrypted postcardThe third NSA Monday ChallengeChristlieb Funk’s challenge cryptogramUnsolved cryptogramsThe Voynich manuscriptThe cigarette case cryptogramNSA’s fourth Monday ChallengeThe Moustier altar inscriptions
Chapter 6: Homophonic ciphers
How homophonic ciphers workHow to detect a homophonic cipherHow to break a homophonic cipherSuccess storiesThe first Zodiac message (Z408)The Zodiac Killer’s second message (Z340)Ferdinand III’s lettersA postcard from HawaiiChallengesA message to the Zodiac KillerEdgar Allan Poe’s second challengeUnsolved cryptogramsBeale Papers #1 and #3The Zodiac Killer’s third message (Z13)The Zodiac Killer’s fourth message (Z32)The Scorpion cryptogramsHenry Debosnys’s messages
Chapter 7: Codes and nomenclators
CodesNomenclatorsTerminologyThe history of codes and nomenclatorsSuperencryption of codes and nomenclatorsHow to detect a code or nomenclatorHow to break a code or nomenclatorFinding the nomenclator table or codebookExploiting weaknesses of codes and nomenclatorsSolving codes and nomenclators with cribsSuccess storiesA telegram sent to Tel AvivEncrypted messages by Mary, Queen of ScotsCollinson’s search expeditionThe Japanese JN-25 codeChallengesThe Mount Everest telegramUnsolved cryptogramsThe silk dress cryptogramThe train station robbery cryptogramA Pollaky newspaper advertisementLord Manchester’s letter
Chapter 8: Polyalphabetic ciphers
How a polyalphabetic cipher worksVigenère cipherOther polyalphabetic ciphersOne-time padHow to detect a polyalphabetic cipherHow to break a polyalphabetic cipherWord guessingChecking for repeating patterns (Kasiski’s method)Using the index of coincidenceDictionary attacksTobias Schrödel’s methodOther Vigenère breaking methodsHow to break a one-time padSuccess storiesThe Diana Dors messageKryptos 1 and 2The Cyrillic ProjectorThouless’s second cryptogram from the cryptThe Smithy CodeChallengesThe Schooling challengeA German radio message from the Second World WarUnsolved cryptogramsWood’s cryptogram from the crypt
Chapter 9: Complete columnar transposition ciphers
How complete columnar transposition ciphers workHow to detect a complete columnar transposition cipherHow to break a complete columnar transposition cipherThe arrange-and-read methodVowel frequencies and multiple anagrammingSuccess storiesDonald Hill’s diaryThe Pablo Waberski spy caseChallengesThe Lampedusa messageThe Friedmans’ love messagesAn encrypted “agony” adYardley’s eleventh ciphergramEdgar Allan Poe’s first challengeAn IRA message
Chapter 10: Incomplete columnar transposition ciphers
How an incomplete columnar transposition cipher worksHow to detect an incomplete columnar transposition cipherHow to break an incomplete columnar transposition cipherSuccess storiesKryptos K3Antonio Marzi’s radio messagesChallengesYet another IRA messageThe Double Columnar Transposition Reloaded challengeUnsolved cryptogramsThe Catokwacopa ad series
Chapter 11: Turning grille transposition ciphers
How turning grille encryption worksHow to detect a turning grille encryptionHow to break a turning grille encryptionSuccess storiesPaolo Bonavoglia’s turning grille solutionAndré Langie’s turning grille solutionKarl de Leeuw’s turning grille solutionThe Mathias Sandorf cryptogramChallengesThe Friedmans’ Christmas cardJew-Lee and Bill’s CryptocablegramA MysteryTwister challengeA Kerckhoffs cryptogram
Chapter 12: Digraph substitution
How general digraph substitution worksHow the Playfair cipher worksHow to detect a general digraph substitutionHow to detect a Playfair cipherHow to break a digraph substitutionFrequency analysisDictionary attacksManual attacksSuccess storiesThouless’s first messageThouless’s third messageChallengesThe cryptogram in National Treasure: Book of SecretsUnsolved cryptogramsThe world record digraph challengeThe world record Playfair challenge
Chapter 13: Abbreviation ciphers
How abbreviation ciphers workHow to detect an abbreviation cipherHow to break an abbreviation cipherSuccess storiesEmil Snyder’s bookletChallengesA birthday cardUnsolved cryptogramsThe Tamám Shud mysteryTwo unsolved postcards
Chapter 14: Dictionary codes and book ciphers
How dictionary codes and book ciphers workHow to detect a dictionary code or book cipherHow to break a dictionary code or book cipherIdentifying the book or dictionaryReconstructing the dictionaryTreating a book cipher like a simple substitution cipherSuccess storiesThe FIDES adsNicholas Trist’s key bookHow William Friedman broke a Hindu conspiracy encryptionA dictionary code message sent to Robert E. LeeChallengesDan Brown’s book cipher challengeA dictionary code challengeUnsolved cryptogramsTwo encrypted newspaper advertisements from 1873
Chapter 15: Additional encryption methods
Cipher toolsVoice encryptionCode talkingShorthand (stenography)Hidden messages (steganography)Success story: How Elonka found a hidden message on a tombstoneSuccess story: Deciphering SteganographiaSuccess story: Mysterious Stranger messageChallenge: Another steganographic message by the FriedmansCipher machines
Chapter 16: Solving ciphers with hill climbing
Solving simple substitution ciphers with hill climbingSimulated annealingSuccess story: Bart Wenmeckers’s solution to the Baring-Gould cryptogramSuccess story: The Florida murder case cryptogramSolving a homophonic cipher with simulated annealingSuccess story: Dhavare, Low, and Stamp’s Zodiac Killer solutionsSolving a Vigenère cipher with hill climbingSuccess story: Jim Gillogly’s solution to IRA Vigenère cryptogramsSolving a columnar transposition with hill climbingSuccess story: Jim Gillogly’s solution to IRA transposition cryptogramsSuccess story: Richard Bean’s solution to the last unsolved IRA cryptogramSuccess story: George Lasry’s solution of the double columnar transposition challengeSolving a turning grille cipher with hill climbingSuccess story: Bart Wenmeckers’s solution to a turning grille cryptogramSuccess story: Armin Krauss’s solution to a turning grille challengeSolving a general digraph substitution with hill climbingSuccess story: Some digraph challengesSolving a Playfair cipher with hill climbingSuccess story: Dan Girard’s solution to the Cheltenham Letter StoneSuccess story: Playfair world recordsSolving machine ciphers with hill climbingSuccess story: Breaking original Enigma messages
Chapter 17: What next?
More unsolved cryptogramsThe fourth Kryptos message (K4)The Rubin cryptogramRicky McCormick’s encrypted notesThe carrier pigeon message from World War IIThe encrypted NKRYPT pillarsEven more unsolved cryptogramsCodebreaking toolsOther books about codebreakingWebsites about codebreakingJournals and newslettersEvents
Appendix A: Kryptos
Appendix B: Useful language statistics
Appendix C: Glossary
Appendix D: Morse code
Appendix E: Figure sources
Appendix F: References
Index

Content preview from Codebreaking

12 Digraph substitution

In his 1563 book De Furtivis Literarum Notis, Italian polymath and cryptologist Giambattista della Porta (1535–1615) proposed an interesting encryption method. Instead of replacing single letters, his system substituted letter pairs (also known as digraphs). In the centuries that followed, different variants of this digraph substitution were developed—including the so-called Playfair cipher. In this chapter, we will cover both methods: Playfair and Porta’s original system.

How general digraph substitution works

The method Giambattista della Porta suggested is based on a digraph substitution table with 400 unique entries. ...

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Codebreaking

by Elonka Dunin, Klaus Schmeh

12 Digraph substitution

How general digraph substitution works

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