Codebreaking: A Practical Guide, Expanded Edition

  • 7h 33m
  • Elonka Dunin, Klaus Schmeh
  • No Starch Press
  • 2023

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.

About the Author

Elonka Dunin is an experienced crypto expert and maintains a list of the world's most famous unsolved codes on her website. Bestselling author Dan Brown even named one of the characters in his Da Vinci Code sequel, The Lost Symbol, after her: “Nola Kaye” is a scrambled form of “Elonka." She is co-founder and co-leader of a group of cryptographers who are working hard to crack the final cipher on the famous Kryptos sculpture at CIA Headquarters, and in 2021 she was invited to give the TEDx talk "2,000 Years of Ordinary Secrets."

Klaus Schmeh is the most-published cryptology author in the world. He has written 15 books (in German) about the subject, as well as over 200 articles, 25 scientific papers, and 1,500 blog posts. He is a member of the editorial board of the scientific magazine, Cryptologia. Schmeh's main fields of interest are codebreaking and the history of encryption. His blog Cipherbrain is read by crypto enthusiasts all over the world. Schmeh is a popular speaker, known for his entertaining presentation style involving self-drawn cartoons and LEGO® models.

In this Book

  • How can I Break an Encrypted Message? And other Introductory Questions
  • The Caesar Cipher
  • Simple Substitution Ciphers
  • Simple Substitution Ciphers without Spaces between Words: Patristocrats
  • Simple Substitution Ciphers in Non-English Languages
  • Homophonic Ciphers
  • Codes and Nomenclators
  • Polyalphabetic Ciphers
  • Complete Columnar Transposition Ciphers
  • Incomplete Columnar Transposition Ciphers
  • Turning Grille Transposition Ciphers
  • Digraph Substitution
  • Abbreviation Ciphers
  • Dictionary Codes and Book Ciphers
  • Additional Encryption Methods
  • Solving Ciphers with Hill Climbing
  • What Next?