Codebreaking cover


A Practical Guide
by Elonka Dunin and Klaus Schmeh
August 2023, 488 pp.

Look Inside!

Codebreaking pages 78-79Codebreaking pages 126-127Codebreaking pages 224-225

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 Bio 

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.

Table of contents 

Chapter 1: How can I break an encrypted message? And other introductory questions
Chapter 2: The Caesar cipher
Chapter 3: Simple substitution ciphers
Chapter 4: Simple substitution ciphers without spaces between words: Patristocrats
Chapter 5: Simple substitution ciphers in non-English languages
Chapter 6: Homophonic ciphers
Chapter 7: Codes and nomenclators
Chapter 8: Polyalphabetic ciphers
Chapter 9: Complete columnar transposition ciphers
Chapter 10: Incomplete columnar transposition ciphers
Chapter 11: Turning grille transposition ciphers
Chapter 12: Digraph substitution
Chapter 13: Abbreviation ciphers
Chapter 14: Dictionary codes and book ciphers
Chapter 15: Additional encryption methods
Chapter 16: Solving ciphers with hill climbing
Chapter 17: What next?
Appendix A: Kryptos
Appendix B: Useful language statistics
Appendix C: Glossary
Appendix D: Morse Code
Appendix E: Figure Sources

View the Copyright page
View the detailed Table of Contents
View the Index


Codebreaking: A Practical Guide is quite the best book on codebreaking I have read: clear, engaging, and fun. A must for would-be recruits to GCHQ and the NSA!”
—Sir Dermot Turing, author of Prof, the biography of his uncle, Alan Turing

“Riveting. Dunin and Schmeh show us that we each have our own inner code-breaker yearning to be set free. Codebreaking isn’t just for super-geniuses with supercomputers; it’s something we were all born to do.”
—Mike Godwin, creator of Godwin’s law and former general counsel for the Wikimedia Foundation

“This is THE book about codebreaking. Very concise, very inclusive, and easy to read. Good references for those who would make codes, too, like Kryptos.”
—Ed Scheidt, CIA

“A compendium of historical cryptography. Approachable, accessible, this book brings back the joy I felt when I first read about these things as a kid.”
—Phil Zimmermann, creator of PGP encryption and inductee into the Internet Hall of Fame

“One of the most helpful guides outside the NSA to cracking ciphers. But even if you don’t become a codebreaker, this book is full of fascinating crypto lore.”
—Steven Levy, New York Times best-selling author of Crypto, Hackers, and Facebook: The Inside Story

“Another kind of Applied Cryptography.”
—Whitfield Diffie, Turing Laureate and creator of public-key cryptography

“This is the book of my dreams. Super-clear, super-fun guide for solving secret messages of all kinds.”
—Jason Fagone, author of the best-selling book The Woman Who Smashed Codes

“Kool dnoces a htrow era snootrac eht fo ynam.”
—Suomynona Ecila

“A wonderful mix of ciphers, both famous and little-known, solved and unsolved. Beginners will be hooked on exploring the world of secrets in cipher, and those who have already been introduced to the field will find much that is new.”
—Craig Bauer, editor in chief of Cryptologia and author of Unsolved!: The History and Mystery of the World’s Greatest Ciphers

“Cryptography? Ciphers? I thought this would be an easy book to put down. I was very wrong.”
—Steve Meretzky, co-author with Douglas Adams of The Hitchhiker’s Guide to the Galaxy computer game

"Fun, fascinating, and user friendly . . .  Expertly written, organized and presented, [Codebreaking] is unreservedly recommended as a supplemental Code Breaking curriculum textbook."
—Midwest Book Review