HISTORY OF THE KL-7 ADONIS & POLLUX - THE FINAL UPDATE? 15 November 2025

We have just published version 5.3 of the history of the TSEC/KL-7 cipher machine. Our first encounter with the KL-7 was in 2005 aboard the battleship HMS Belfast, where it was displayed behind glass. It then took six more years of research to create an accurate simulation of this Cold War cryptologic marvel. None of this would have been possible without the help of Paul and Marc from the Crypto Museum, the late George Mace, and Bill Neill’s FOIA contributions. Their assistance was invaluable in unraveling the technology behind the KL-7.

The William Friedman Collection was a treasure trove that detailed the design choices and development of the KL-7. Historical records from the U.S. Army Security Agency contained production details, planning and procurement, and reports on its use in Vietnam. The first version of the KL-7 history was published in 2022 and included references to all relevant ASA, AFSA, NSA, CIA, and NATO files. In the following years, many more documents and bits of information surfaced, including FBI documents and counterintelligence records about the KL-7's compromise by John Walker and Joseph Helmich. The research began in 2005, and although all technical documents were declassified in 2009, the research ultimately took nearly two decades as additional records were released gradually.

The newest version offers the most detailed history of the TSEC/KL-7 ever published, but research continues. Its use of electronics, worldwide deployment in both war and peace, and involvement in espionage cases make the KL-7 a true Cold War icon, deserving its place in cryptologic history.

This is the definitive history of the KL-7 unless we discover additional information. Former operators and technicians can help us preserve cryptologic history by sharing personal experiences with the now-declassified KL-7. We already documented stories from a U.S. crypto tech at the Air Base Saigon, a U.K. tech at JHQ Rheindahlen, and a British merchant radio operator during the Falklands War. However, more stories about the KL-7 are essential to preserve its history.

More about the TSEC/KL-7 in English or Nederlands with all technical details and full history.

PAPERS FROM MATHEMATICIAN ALAN TURING AUCTIONED 19 June 2025

Alan Turing

A collection of articles written by renowned mathematician, codebreaker, and computer pioneer Alan Turing was sold last Tuesday for a record-breaking £465,400 by Hansons Auctioneers. However, these papers were almost destined to be lost forever. The story starts in the 1930s, when Turing wrote some of the most important papers on early computing. Those papers and several personal letters were later a gift from Alan Turing's mother, Ethel, to his friend Norman Routledge, a British fellow mathematician.

When Routledge passed away in 2013, the papers were discovered by his sister, who took them home. When the sister moved to a care home, her daughters found the collection. Luckily, before putting the papers in the shredder, they asked the family if the papers had any value.

The collection included, among others, the following documents, price included. From the Turing Digital Archive (links open in new tab). Please consult copyright terms of use.

• On Computable Numbers 1936-37, the foundation for modern computer science and theory of numbers, computation, and algorithms, also known as Turing's Proof, £208,000.
• Systems of Logic Based on Ordinals 1938-39, Turing's PhD dissertation on how to construct an hierarchy of formal systems and the limits of computing, £110,500.
• The World Problem in Semi-Groups with Cancellation 1950, on the theory of undecidable problems in algebra and the limits to find a general solution, £28,600.
• Computability and Lambda-Definability 1937, formalization two concepts Turing and Church in the theory of computation. What can be solved, and by different systems, £26,000.
• The Chemical Basis of Morphogenesis 1952, the reaction-diffusion theory and how a simple chemical reaction can develop into different complex biological organisms, £19,500.
• Equivalence of Left and Right Almost Periodicity 1935, the almost periodicity and left and right shift pattern's nature works both ways, useful for analyzing patterns, £7,800.

Alan Turing's theoretical foundation for computers science and modern computers.
© Copyright London Mathematical Society 1937

More information on the auction at the Hanson Auctioneers website, and the two BBC stories on how they Nearly Shredded the Papers and Saved the Alan Turing Papers. And if you're reading this news item on your computer, you definitely should thank Alan Turing.

20 YEARS OF CRYPTOLOGIC CHALLENGES 18 February 2025

This year marks the 21st anniversary of our Enigma simulator and the 20th year of cryptologic challenges. It all started in early 2006 with the Enigma Challenge to decrypt ten messages. Although the challenge was a one-time event, the feedback encouraged us to continue the challenge. The original 2006 results are included in the all-time Table of Honor of the currently running challenge.

The Enigma, Crypto Box, and TSEC/KL-7 ADONIS

In the following years, we introduced four more challenges, each with its own Table of Honor that lists all participants. The crypto machine simulations in the Enigma Challenge and Operation Tinker Bell work exactly like the real machines, making for an authentic experience.

Some challenge statistics (updated 10 Dec 2025)

Enigma Challenge (est. 2006)

Currently, 366 participants from 46 countries solved 2,458 messages. This challenge is quite accessible and no expert knowledge of cryptologic techniques is required. This challenge serves as an introduction to codebreaking. Most participants get quite far with logical thinking, patience, and some perseverance, with 55% of them solving eight to ten messages. Visit in English or Nederlands.

Crypto Box Challenge (est. 2007)

This transposition cipher is more difficult and 87 participants from 26 countries submitted 160 solutions. The first Crypto Box is not that difficult, but complexity increases rapidly. To this day, only 13% of the participants solved the three boxes and 87% solved one or two boxes, which is quite meritorious, given the difficulty level. Some cryptanalytic knowledge is useful but hard work also pays off. Visit in English or Nederlands.

Operation Tinker Bell (est. 2013)

This is an accessible cryptologic spy adventure set in an authentic Cold War atmosphere, focusing on secure communications between intelligence agencies and their agents and operatives in the field. No cryptologic skills are required. All authentic crypto tools, keys, and instructions are provided to solve the case. Those who complete the mission have their names engraved on the Wall of Honor. Currently, the operation has been completed by 33 participants who deciphered a total of 1,716 messages. Visit this challenge only in English.

Elite Box Challenge (est. 2022)

The Elite Box is the Crypto Box on steroids. To this day, only one person managed to solve two out of the three boxes, and four participants solved one box. The first box already starts with a higher number of steps, there's one box with an unknown number of steps, and one box has an unknown type of fractionated characters, requiring more than simply shifting rows and columns. Cryptanalytic techniques are required to solve this one. Visit in English or Nederlands.

The Crow's Cryptogram (est. 2010)

Although already published in 2010, there's a good reason why the Crow's Cryptogram is the last one on our statistics list. Encrypted oncly with a pencil-and-paper system, this one comes with a single hint and has 600 digits in 120 five-digit groups. The bleak statistics: only one person ever solved this cryptogram. Expertise in cryptanalytic techniques is required. Visit in English or Nederlands.

If you're in for a cryptologic adventure, enjoy the challenges!

SECOND ELITE BOX CRACKED BY MAGNUS EKHALL 04 December 2024

Magnus Ekhall just solved a second box from the Elite Box challenge, the successor to the still-running Crypto Box Challenge. In both challenges, the participants decrypt three short texts by shifting the rows and columns in a small text square. Retrieving the original text has proved to be a real challenge, as even a few shuffles create a true brain-teasing puzzle.

The Crypto Box Challenge started in 2007, and over the years, participants from 26 different countries have entered the challenge. We therefore started the Elite Box Challenge in 2018. However, the Elite Boxes are far more difficult than the Crypto Boxes, and cryptanalytic techniques can be useful to solve them. We therefore recommend first training your skills on the Crypto Box Challenge, although not it's not mandatory.

You can enter the English Crypto Box challenge and Elite Box Challenge. These challenges are also available at the Dutch/Nederlandse pages, but those scrambled texts are identical to the English version to make the challenge equally difficult for everyone.

THE 2024 GCHQ CHRISTMAS CHALLENGE IS ANNOUNCED 19 November 2024

The Government Communications Headquarters has announced its annual series of Christmas puzzles. Their job is making and breaking codes and providing secure communications, but once a year, a GCHQ team of smart puzzlers creates a series of true brainteasers. The challenge is designed to tickle the interest of young people, ages 11 to 18, who must work in teams and use all their out-of-the-box thinking skills, some of which are useful for becoming a spy. However, those age 19 to 99 can also sink their teeth in the challenge, as there's no age limit on using your brain.

To know what you're up against, and to train your skills, download the 2022 and 2023 challenges and their solutions to get an idea of the various types of puzzles and how to find solutions to solve them. Of course, each year, the creative GCHQ brains come up with new types of puzzles, but the previous challenges might inspire you to find ways to solve the 2024 challenge.

The 2024 Christmas Challenge goes live for the general public on Wednesday 11 December 2024, but schools can already register to get early access to the challenge and lesson planning materials. For more details and how schools can register, visit the GCHQ Christmas Challenge page.

Update 11 December: The 2024 Christmas Challenge is now online. Good luck to all participants!

ENIGMA TOUCH PRESENTED ON e-BASTELN WEBSITE 05 November 2024

Jürgen Müller just published the Enigma Touch, a single-board design of no less than 13 different Enigma versions. These include the early Enigma D version, the four Abwehr versions, the Railway Enigma, the military versions Enigma I, M3, and M4, and the various commercial K versions, including the Swiss K and the Japanese Tirpitz. The plugboard is also detachable, which enables the use of a wooden Enigma case where the plugboard is placed vertically.

However, Jürgen resurrected many other machines. The Vintage Computing section includes the Tiny ACE, the LittleGP-30, RPC-4000, LGP-21, Telefunken Rollkugel, and a tiny optical punched paper tape reader. There's also the 65F02, a 6502 programmed in an FPGA, which emulates the legendary, groundbreaking MOS 6502 8-bit processor, used on the KIM-1, Apple II, Commodore PET, and many other computers.

He also developed the Asteroids Mini, Pong, and the Verticade arcade console with a whole range of 70s and 80s games. Other projects include his STM Scanning Tunneling Microscope, and even a breadboard watch he rightly calls the Nerd’s Wristwatch.

Visit the Enigma Touch page to discover all the nuts and bolts of this wonderful project. Although the website is fully in English, the name e-basteln comes from the German word for tinkering, crafting, or creating, which is exactly what Jürgen has done with passion in the past 25 years. Moreover, all projects come with detailed documentation. Do visit the e-Basteln website.

News Update 25 June 2025! The Enigma Touch is now available for sale and comes fully assembled and tested by CDES. More details are available at the Obsolescence Guaranteed website.

OPERATION TINKER BELL CRYPTO SPY ADVENTURE HAS MOVED 29 Oct 2024

Operation Tinkel Bell has moved to the Cipher Machines and Cryptology website. Originally hosted on Blogger, the move offers more flexibility for HTML, maintenance, and a broader audience. If you love spy stories, secret operations, and cryptology, this adventure is a perfect mix.

The year is 1964. Operation Tinker Bell takes place at the height of the Cold War and you are assigned to the operation as COMSEC officer. Your task is to decrypt the message traffic between intelligence agencies, their stations abroad, and agents in the field.

This sounds harder than it actually is. All required crypto tools, keys, and clear instructions are provided, and you get the proper training to work with state-of-the-art crypto equipment and manual ciphers. If you successfully decrypt all messages, your name is engraved in the Wall of Honor.

You will experience spy tradecraft firsthand. CIA transmitter sites in West Germany, illegal border crossings, fake passports, safe houses, the dreaded East German Stasi and Czech StB secret police. British intelligence helps to arrange clandestine meetings, the U.S. Army Security Agency provides SIGINT support and some USMLM operations don't take the rules of engagement too seriously. The Cold War at its best, authentic details, many historical photos, as real as it gets.

THE CODEBREAKERS INTERNATIONAL ONLINE CONTEST 10 Oct 2024

Great news for those who love cryptologic challenges! The new edition of theCODEBREAKERS is online. The contest is dedicated to Marian Rejewski, Jerzy Rózycki, and Henryk Zygalski, the three Polish codebreakers who were in 1932 the first to break the encryption of the German Enigma cipher machine.

The contest website features lectures where you can learn more about the history of cryptography, different codes, and of course the tasks and codes. There are three levels, each with its own starting date, and the website is now available in nine languages.

You can already register and play the single-players trial level, and to participate in the contest, you register a team in the levels you want to solve, and you can invite two more players for a three-person team. Each level consists of several stages, each with lectures and tasks to solve. The BASIC level game with tasks in English will start soon.

Make sure to be prepared and registered in time for the start of the competition:

• TRIAL Open
• BASIC 21 October
• ADVENTURE 15 November
• ENIGMA 29 November

Visit theCODEBREAKERS website for more information and follow their Facebook to catch the latest news. You can also promote their website and contest by sharing their poster and flyer. See also the Codebreakers introduction video below.

THE ENIGMA MACHINE IN MECCANO 02 Oct 2024

Software developer Craig Longhurst has always had a keen interest in all things technical. In 2002, he got the idea of building a working Enigma, the well-known German cipher machine of which various civil and military versions were produced from 1923 throughout the Second World War.

Craig decided to build the famous Enigma I, but designing the rotors with their internal wiring and contacts proved complex. Over the years, he learned laser cutting for the rotor contact holes and later 3D printing for the discs. These were only a few of the many obstacles that required quite a bit of work and imagination, not only to construct the electrical parts but also various mechanical components, all made with Meccano parts.

Although he considered the rotors the most difficult part, it would be quite an understatement to call the Meccano construction of the Enigma, the keyboard with numerous switches, the contacts, and lamp panel "easy". The result of his creativity was a fully working Meccano Enigma I in 2024.

Craig's Enigma is published in the Constructor Quarterly issue No. 145 and if you're interested in Enigma and Meccano, you're in for a real treat. The issue has 16 pages on his Enigma, with 26 excellent highly detailed photos of all parts, accompanied by information about the development and construction. Available as back issue, sent all over the world. In the video, you get an idea of how complex Craig's project was, and why it took 22 years to complete his award-winning Enigma.

DECODING THE LETTERS OF MARY, QUEEN OF SCOTS 29 Sep 2024

When George Lasry, Norbert Biermann and Satoshi Tomokiyo started deciphering more than fifty letters they found in the Bibliothèque Nationale de France, they unexpectedly discovered that these were letters presumed lost, written by the imprisoned Mary, Queen of Scots (1542-1587).

In 1567, Mary Stuart was forced to abdicate, and imprisoned in the Scottish castle of Lochleven, but escaped the next year to England. Since Mary had a claim to the English throne, she was a threat to her cousin, Queen Elizabeth I, who kept her captive in England. Still, Mary remained involved in plots to take the throne.

In 1586, Anthony Babington, the leader of a plot to assassinate Queen Elizabeth, established a secret communications channel for Mary Stuart. However, Sir Francis Walsingham, secretary and spymaster of Elizabeth, had placed several spies in Mary's circle, compromising the Babington plot. When Mary did not object to the assassination of Elizabeth in a letter to Babington, she sealed her fate. Her conspirators were executed in September 1586, and Mary Stuart, 44 years old, followed on 8 February 1587.

Mary was known to correspond with her allies through encrypted letters, but many of those were believed to have been lost. Most of the recently discovered letters were addressed to Michel de Castelnau, the French ambassador to London. Although they are 445 years old, deciphering them still proved to be a complex task for the codebreakers. The team later found plain-text versions of some of those letters in the British Archives, leaked to Walsingham by a mole in the French Embassy. These confirmed the correct deciphering of some messages from the Bibliothèque Nationale de France.

A fascinating story of deceit and treason, uncovered by the three talented codebreakers in 2023. Their codebreaking achievement is published in detail on Cryptologia. On the Cryptiana website are the ciphers of Mary, Queen of Scots, the discovery and codebreaking of 50+ letters, and simulated paper-and-pencil codebreaking of a ciphered letter. See also the DECRYPT project.

Below the excellent talk by George Lasry, explaining in detail how they deciphered the messages, and to understand the animosities between Mary and Elizabeth, watch the BBC documentary.