Two of the world’s leading experts, Elonka Dunin and Klaus Schmeh, reveal their codebreaking methods and stories. This book has over 100 examples of historical ciphers, the context around them, and how they were broken. The first edition was released in the UK in December 2020, with a new Expanded Edition (25% new content!) available in the US on September 19, 2023.

Click here to find out about all the new stuff, or go to the No Starch Press website where you can purchase a book right now! 

Cover of "Codebreaking: Expanded Edition". A cartoon robot is working on a code, while holding a Jefferson cipher cylinder. Behind the robot, a faint set of unusual symbols can be seen.

New Expanded Edition (25% new content!) available in the US on September 19, 2023!

UK (1st edition): December 10, 2020

Germany (1st edition): December 10, 2020

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

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, inductee to 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 bestselling author of Crypto, Hackers, and Facebook: The Inside Story

The enthusiasm of the writing will likely pull the reader through the book . . . a good introduction to cryptology.
Chris Christensen, Cryptologia

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

Riveting. Dunin and Schmeh show us that we each have our own inner codebreaker 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, former general counsel, Wikimedia Foundation

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

Exciting, challenging, mysterious, this is the book on cryptography that you must have. If you are not yet addicted to cryptography, this book will get you addicted. Read and enjoy!
Jared Diamond, Pulitzer Prize-winning author of Guns, Germs and SteelCollapse; and other international bestsellers

This comprehensive book provides separate chapters for just about every major encryption scheme historically used
Satoshi Tomokiyo, Cryptiana

This is the book of my dreams: A super-clear, super-fun guide for solving secret messages of all kinds, from paper-and-pencil cryptograms to Enigma machines. With deep knowledge and skillful storytelling, Dunin and Schmeh capture the joy and power of codebreaking.
Jason Fagone, author of the bestselling The Woman Who Smashed Codes

A terrific cognitive romp through some of the most important puzzlers, challenges, sizzlers and stumpers throughout history.
Dr. Constance Steinkuehler, Informatics Professor, University of California, former Senior Advisor in the White House Office of Science and Technology Policy

A fantastic resource, full of great stories of the deduction, intuition, and perseverance involved in codebreaking, along with the tales of how codebreakers have used their tools to attack seemingly unbreakable ciphers.
Wes Dafler, American Cryptogram Association (DARING FLAIR)

An incredible, practical, up to date resource for codebreaking which has not existed up till now. I cannot wait to use this book.
Starr Long, former executive producer, Walt Disney Company

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

If you’re looking for a source book to learn the art and science of cracking codes, it’s hard to find a better collection than the deep and well-documented collection in this book. The original cryptext is there along with the mathematical and practical tools for stripping away the layer of secrecy to read the information hidden inside. It’s a practical treasure for empowering your code breaking skills.
Peter Wayner, author, Disappearing Cryptography, Being and Nothingness on the Net

A fascinating glimpse into the world of ciphers, codes, and secrets. It works equally well as a primer for the novice and as a reference for the enthusiast. Nznmvat!
Raph Koster, author of the bestseller A Theory of Fun

I have been a creator and solver of puzzles both virtual and physical my whole life, I even gave my wife a GPS-enabled puzzle box as a wedding present to lead her to our honeymoon. That being said, I could hardly imagine even approaching the problems Elonka Dunin and Klaus Schmeh have tackled. Fortunately for my ego, there remain a few even Elonka has not yet solved. However, if you wish to start down the rabbit hole, there is no better place to start than Codebreaking: A Practical Guide. I even hear that there are a few other hidden secrets embedded in this book! Good luck!
Richard Garriott, computer gaming pioneer (“Lord British”, Ultima Online) & private astronaut

As an author of crypto books and a crypto blog, I regularly get requests to solve encrypted postcards. Then, it is not easy to find appropriate help on my bookshelf. While cryptology fans have become gradually spoiled by informative books and journal articles on various historical ciphers and codes, practical methods of codebreaking – and I do not mean the sophisticated computer algorithms – are rarely published on an easily accessible level.

This book is one of the rare exceptions. It is amateur friendly, up to date, and offers pencil-and paper methods, easy to grasp even by non-professional codebreakers without special mathematical skills, to detect and break cryptograms. It systematically surveys the main encryption methods in a fresh way. What I love in the book is its approach. The specific methods are not demonstrated by the well-known textbook examples, rather by (often unknown) real life cases, such as 19th century newspaper ads, prison messages and civil war diaries, encrypted journals and even everyday objects, such as a mug from a museum gift shop. With its lovely codebreaking demonstrations, this book is a real starting manual for any crypto novice.
Benedek Láng, Chair of Philosophy and History of Science Department, Budapest University of Technology and Economics

A comprehensive, yet accessible, resource for a contemporary understanding of the past and present of codebreaking. The kind of resource that is useful for beginners, yet encyclopedic for more experienced readers.
Lindsay Grace, Knight Chair of Interactive Media, University of Miami, School of Communication

As a long-time writer and speaker on codes and ciphers, Elonka Dunin knows her stuff. Together with co-author Klaus Schmeh, she put together a practical and engaging guide to codes and ciphers that have been used throughout the last several centuries, long before computers were available to aid the process. As a major hint to would-be codebreakers, the story behind the code is often as important and compelling as a code itself, and Dunin and Schmeh never fail to deliver with each code they examine. Enjoy, and happy codebreaking!
Scott M. Jones, Director, Electronic Frontiers Forums track at Dragon Con, Atlanta

A great resource for all types of codes and ciphers, and covers different parts of history and cultures with the respect that is deserved, including for Native Americans.
Lonnie Henderson, MSgt USAF (ret), Comanche “Code Breaker”

Wow! A book that promises to break the code to codebreaking itself. For more than a decade, I led a team of experts trying to decipher the levels of meaning in the pop culture works of Dan Brown. Through the publication of several such guidebooks, Elonka Dunin stood out as primus inter pares among our experts on codes. I am putting this book on gift lists for many occasions and for numerous people!
Dan Burstein, author and editor of the New York Times bestseller, Secrets of the Code

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

The crypto explorer’s Baedeker travel guide. It introduces you to a variety of both famous and lesser known cryptograms throughout time, while it guides you carefully through the various processes of unraveling their secrets.
Frode Weierud, CERN electronics engineer (ret), Visiting Research Scholar, Bletchley Park Trust

Plainspoken and informative, Codebreaking: A Practical Guide shows the incredible depth of knowledge of the two authors while retaining a clarity most books of this sort have trouble duplicating. Both experts and novices will enjoy exploring the pages of this wonderful tome.
John Feil, International Game Developers Association

Excellent! Both well-documented and pleasurable, it overviews all classical ciphers and explains them with exemplary clarity. Good for amateur cryptographers, or those who wish to have historical background as they proceed in a journey towards the more mathematical aspects of modern cryptology. A must have in all libraries!
David Naccache, Fellow, International Association for Cryptologic Research

Cryptography can seem like a daunting subject, but in this book Elonka and Klaus have made it understandable, approachable, and most of all: fun! Filled with many real-world examples of the use of classical cryptography techniques, the book successfully conveys the authors’ contagious passion for the art of uncovering hidden messages. There is nothing quite like the satisfaction of applying the skills described in this book to unlock the mysterious secret messages. After reading this book you will be equipped with many tools to help you do it, too!
Dave Oranchak, founder of and host of Let’s Crack Zodiac

Dunin and Schmeh, two internationally known experts on cryptology, show you step by step how to crack codes and ciphers from before the earliest radio transmissions to the world of contemporary computing.
Peter Krapp, Professor of Media Studies and Informatics, University of California, Irvine

Throw Your Other Books Away. Codebreaking goes well beyond the “how” by including historical examples, practical attacks, and challenges to solve. This high-quality cryptography resource is all you need to truly understand many ciphers.
Tyler Akins, Developer, Cipher Tools

A cipher is a delicate balance. On the one hand, you want a system that is complex enough to evade prying eyes. On the other hand, you want your message to reach its intended reader without difficulty. Consider this an introductory textbook on ciphers and codebreaking. Elonka Dunin and Klaus Schmeh take a fresh approach to the art of codebreaking with an extensive look at some of the most famous ciphers in history (both cracked and uncracked). Each chapter details a new cipher technique while stressing the craft’s terminology, and each historical example comes with a complete backstory. The reader will learn how to use each cipher as well as the best approaches when attempting to attack an uncracked cipher with a step-by-step guide. Computer software is often required to crack the most robust ciphers. Still, the reader will have a better understanding of how these applications operate with complete descriptions of the relevant algorithms, such as hill climbing and dictionary attacks, in layman’s terms. This book treats each cipher as a mystery waiting and wanting to be solved and eagerly invites the reader to share in the excitement of cracking ciphers.
Dr. James Church, Associate Professor at Austin Peay State University, author of “Learning Haskell Data Analysis”

Best suited for those who want to read about codebreaking with actual examples. Many specimens with images, ranging from encrypted postcards to historical messages, are conveniently classified in chapters and their solutions are explained.
Satoshi Tomokiyo, webmaster of Cryptiana: Articles on Historical Cryptography

A book with many interesting stories behind real historic cryptograms. These are clustered according to the ciphers behind. And the best thing: You are introduced to free and modern software to break them yourself.
Bernhard Esslinger, Professor at University of Siegen for Applied Cryptography

This brilliant, passionate, irresistible book has it all: twisty mystery, codebreaking, secrets, encrypted messages! What’s not to love?
Nancy K. Austin, co-author, New York Times #1 bestselling A Passion for Excellence

If codebreaking were an Olympic sport, these authors have brought home the gold! Pure genius meets joy in this truly one-of-a-kind compendium that is Dunin and Schmeh’s Codebreaking: A Practical Guide. They do the intellectual heavy lifting that will engage any reader in the science and art of encryption. This book will reward everyone from the curious novice to the invested researcher, introducing secrets from the ancient to the modern unsolvable ciphers, all the while providing tools for readers to do their own explorations into the field.
Theda Daniels-Race, PhD, M.B. Voorhies Distinguished Professor of Electrical & Computer Engineering, Louisiana State University

A celebration of historical ciphers and codes – from how they work to how they can be broken. A gentle and enthralling introduction for the novice with scores of challenge problems, a guide for the student of classical cryptology, and a delight for the expert with dozens of unsolved problems to attack.
Dr. Kent D. Boklan, NSA-trained cryptologist, Professor of Computer Science at Queens College, City University of New York

Filled with over 200 classic and little-known enciphered documents and puzzles, this book guides the reader through the underlying principles of encipherment, the principles and processes involved in deciphering, and the ultimate outcome.
Professor Tom Perera, PhD, author of “Inside Enigma”, founder of

Essential reading for anyone interested in solving ciphers. Elonka Dunin and Klaus Schmeh have well-established reputations as skilled writers about cryptology. Their superb book includes over 100 examples of historical ciphers, with explanations of how many were solved, and others for enthusiasts to unravel.
Ralph Erskine, co-editor of The Bletchley Park Codebreakers; member of the editorial board of Cryptologia

A fascinating look into the hidden world of making – and breaking – secret codes and ciphers, filled with intriguing stories of urgent messages sent by criminals, spies, and even lovers throughout history.
Bob Bates, Lifetime Achievement Award recipient, International Game Developers Association

A fun book telling the neat and weird secret histories, plus a practical guide to solving most any cipher. I wish that I had a book like this back when I was in high school.
Brad Schaefer, Founder of the MIT Mystery Hunt, Professor, Physics and Astronomy, Louisiana State University

A roller-coaster ride through the cunning world of ciphers and codes
Nick Pelling, Cipher Mysteries

It was time for a book like this. This masterpiece is both an extension as well as a successor of the existing and nowadays partially outdated works about (unsolved) codes and cryptography – from Helen F. Gaines to David Kahn.
Tobias Schrödel, IT security expert and Comedyhacker, as seen on sternTV

At last a comprehensive book guiding readers through the world of codes and ciphers. Lots of general information for the casual reader, plus plenty of worked examples for enthusiasts.
Joel Greenberg, author of Gordon Welchman: Bletchley Park’s Architect of Ultra Intelligence, and Alastair Denniston: Code-Breaking from Room 40 to Berkeley Street and the Birth of GCHQ

A fascinating collection of the world’s most interesting codes and ciphers and how to break them. Full of facts and fun. A must for anyone who enjoys solving quirky puzzles.
Michael Smith, author of  the #1 bestseller Station X: The Codebreakers of Bletchley Park and The Emperor’s Codes

Strongly recommended for anyone interested in historical ciphers. There are very few books dedicated specifically to the breaking of classical ciphers, with the best known still the 1939 book Cryptanalysis by Helen Fouché Gaines. This new book fills that gap, covering a large number of things never envisioned by Gaines; including hill climbing, the best known contemporary algorithm for breaking ciphers. There are plenty of practical examples and real-world success stories.
Paolo Bonavoglia (ret), teacher of mathematics, Convitto Nazionale Marco Foscarini, Venezia, Italy

This book will take you on an amazing journey through an incredible maze. Exciting!
David Lucas, award-winning composer, discoverer of “Blue Oyster Cult”, the cowbell guy!

Qvjuh huqtydw jxyi reea, yj’i xqht je ijef coiubv vhec mhyjydw uluhojxydw yd syfxuhi! Vehjkdqjubo, Y qc qrbu je huiyij.
Iecuedu Mu Vekdt, Rheaud qdt Ierrydw Ekjiytu qd Uisqfu Heec

I dare you to find a more diverse, a more mind-blowing, a more intriguing collection of stories about codes and code breaking. This isn’t just a book about cryptography and cryptanalysis, it’s a fascinating glimpse into humankind’s use of secrecy and deception to serve a variety of interests.
Yudhijit Bhattacharjee, author of the New York Times bestselling nonfiction thriller, The Spy Who Couldn’t Spell

This book not only breaks down the art of codebreaking in a manner comprehensible ­to a layperson like myself, but it contextualizes it in a series of compelling vignettes; recounting encrypted secrets, schemes and mysteries woven into a history of human dramas, great and small. This combination of puzzle and story makes for an eminently devourable read!
Tracy Butler, author and artist of the award-winning comic Lackadaisy

An inspiring, profusely illustrated encyclopedia of challenges, set in their original cultural and historical context. A delight for experts and beginners. A thoughtful workbook companion to David Kahn’s classic, The Codebreakers.
Nicholas Gessler, PhD Anthropology, UCLA, Duke University (ret). Author, “The Computerman, the Cryptographer and the Physicist,” in Alan Turing: His Work and Impact

I hope this book will inspire more people to take an interest in the exciting hobby of cryptology. Well, at least that one prodigy who finally decodes the Voynich manuscript…
Oliver Knörzer, author of the webcomic Sandra and Woo

I’ll say it in cleartext: This is the most useful book on codebreaking you can have in your library.
A.J. Jacobs, New York Times bestselling author of The Year of Living Biblically and Puzzled: A Deep Dive into riddles, brainteasers, and conundrums of all kinds

A treasure chest with a plethora of historical illustrations and photos chronicling cryptography dating from centuries ago all the way up to today. Abundant rare and high quality photos, and hilarious comics at the beginning of each chapter!

Reading this book has clarified my illusions that older cryptograms were simple, and deeply increased my respect for pencil and paper methods. I’m now better informed about falsehoods that I had assumed, and glad that I now (with this book) have the best opportunity to learn what I did not know before, such as “Hill Climbing” codebreaking techniques (Ch 16). This book also points readers to beginner-friendly open-source computer programs that are easily accessible to help everyone solve old ciphers, or create new ones! 

This is a great gift book for young and old, and a fitting augmentation to any library’s collection. Knowing Elonka, I also strongly suspect some cryptext “Easter-Egg” secrets hidden somehow within this expert tome that she will never reveal (she’s great a keeping secrets!) but will tell you if you guess correctly!
Joe Torre, Senior Hardware Engineer (ret), Amiga Computers

An encyclopedia of practical code breaking with a variety of high profile real-life encrypted messages. It teaches everything from how to solve parts of the famous CIA Kryptos sculpture,  to encrypted prisoner messages and other crime mysteries. The book takes a firm position that such puzzles can actually be solved and decrypted, and provides expert guidance, methodology and examples. It is superbly illustrated and written, once you start reading, it is very hard to stop! It provides solid historical and cryptanalytic and linguistic background knowledge and it has great educational value.
Nicolas T. Courtois, Cryptology lecturer at University College London and author of 150+ papers on cryptography

This is the book we’ve all been waiting for, a page-turner packed with intrigue and mystery — the first practical book on code-breaking for the digital age.  Code experts and enthusiasts Elonka Dunin and Klaus Schmeh patiently explain the basic types of codes and ciphers, and how to detect which scheme is being used. Say you discover an aged letter covered with mysterious symbols tucked into an old book in the attic. An encrypted communication from a long-dead relative, no doubt. But what does it say? Fear no more. With over a hundred cloak and dagger examples, ranging from the Emperor Ferdinand II, the Holy Roman Emperor from the House of Habsburg in the 1640s, to the Zodiac Killer in northern California in the 1960s, this is what you need. What a great way to introduce a new generation to the romance of mathematics!
Scott Kim, TED talk speaker, “The Art of Puzzles”, puzzle designer for Discover and Scientific American magazines

Makes it easy for the reader to do a deep dive into the many codes and ciphers still unsolved. This is a fantastic guide to cryptography, Dunin and Schmeh do a masterful job of explaining most known methods complete with historical commentary.
Dr. Foaad Khosmood, Associate Professor of Computer Science, California Polytechnic State University, co-founder of the Global Game Jam

An invaluable resource to both the professional and the amateur codesmith. Elonka Dunin and Klaus Schmeh have gone to great lengths to create an almost encyclopedic collection of information on how to create and how to break codes. Its coverage is comprehensive, including codes used by prisoners, Edgar Allan Poe, and the Zodiac Killer, 
Jay Wiseman, JD, author and educator, former adjunct professor at New College of California School of Law

Two well-known code-breaking experts have joined forces and produced a book that takes a very practical look into how one solves historical ciphers, with a lot of useful theory along the way.
René Zandbergen, author, The Voynich Manuscript: The World’s Most Mysterious and Esoteric Codex

Cryptography is but a game of secrets — who better than a game developer to walk you through the science, art, and history of this remarkable field?
Dan Kaminsky, security researcher, Chief Scientist, White Ops

Approachable and compelling, a remarkable treatment of the art of decrypting hand-created codes. Clear and conversational in tone, it transforms a sometimes daunting topic into accessible stories. Its comprehensive survey of manual codes and techniques for cryptanalyzing them is thoroughly illustrated with real historical examples, from the Voynich manuscript to the Zodiac Killer’s encrypted messages. An excellent book for starting a deep-dive into cryptanalysis.
Glen Miranker, Chief Technology Officer of Apple Computers (ret)

A fabulous step-by-step guide on how to become an effective codebreaker. Is unique with its number of rich, illustrative, engaging and fun examples and stories.
George Lasry, PhD, master codebreaker, former world record holder for breaking Playfair challenges