20 Years of Cryptologic Challenges

This year will mark the 21st anniversary of our Enigma simulator and entering 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 machine,  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 authentic experience. Below some challenge statistics (updated 12 May 2025):

Enigma Challenge (est. 2006)

Currently, 360 participants from 46 countries solved 2398 messages. This challenge is quite accessible and no expert knowledge on 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 84 participants from 26 countries submitted 160 solutions. The first Crypto Box is not that difficult, but complexity increases rapidly. To this day, only 13% 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 a very accessible cryptologic spy adventure in a true Cold War atmosphere, focusing on secure communications between intelligence agencies, their agents and operatives in the field. You don't need any cryptologic skills. All authentic crypto tools, keys and clear instructions are provided to solve this spy case. The participants who complete the operation get their name engraved in the Wall of Honor. Fun and excitement guaranteed. Visit in English only. 

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 three persons only 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. Only encrypted 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!

Operation Tinker Bell has Relocated to the Website!

Operation Tinkel Bell has moved to the Cipher Machines and Cryptology website. The move offers more flexibility for HTML and maintenance, and a broader audience. It's also easier to switch from the operation to the technical and historical research on the website. If you love Cold War spy stories, secret operations and cryptology, then this is the perfect mix for many exciting hours.

Operation Tinker Bell is a spy case that you solve using cryptography. The year is 1964 and Operation Tinker Bell takes place at the height of the Cold War. You are assigned to the operation as COMSEC officer, and your task is to decrypt the message traffic between intelligence agencies, their stations abroad and agents in the field. All required crypto tools, keys and clear instructions are provided. You get the proper training to work with the TSEC/KL-7 crypto machine, decrypt numbers station broadcasts, and use one-time pad encryption.

You experience spy tradecraft, operations behind the Iron Curtain, illegal border crossings, fake passports and safe houses. CIA transmitter sites in West Germany provide support, and the dreaded East-German Stasi and Czech StB secret police are some of your opponents. 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.

Click the banner and join the operation!

The Cold War at its best, with authentic details, many historical photos, and as real as it gets. If you successfully decrypt all messages, your name is engraved in the Wall of Honor. However, this operation is no walk in the park, and failure is not an option. Read up on the operation in the briefing room, and be prepared.

Note that the old blogger version of Operation Tinker Bell redirects the visitor automatically to the new location at our website.

Podcast Nuggets Episode 11

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We're back with Podcast Nuggets, but this time only two podcasts due to some radio silence. You're nevertheless in for a treat. The first one is from Katerina Urban Richterova, the Slovak award-winning radio journalist and reporter who also worked for the New York Times, CNN, BBC, ARTE, and many more. She's well informed and a joy to listen to. Unlike usual, we don't suggest an episode, but recommend listening to her full podcast series. Somehow, I managed to miss the start of this series in 2020 but it's never too late to discover podcast gems. There's also a fascinating Spycraft 101 episode on Area 51.

The Secret Struggle for Cold War Dominance is a Cold War podcast series, but not about the usual main opponents, although they might be involved in some cases. If we talk about the Cold War, most people know the rivalry between the Unites States, Russia, and later China. However, many lesser known Asian, African and South American countries were also affected and, willingly or not, actively involved in the Cold War. Yet they are barely mentioned in the archives. Katarina interviews researchers about those unknown people and their stories. You can listen to the complete series, including bonus episodes, on Apple Podcast, Spotify or Katarina's podcast page, but make sure to go back to the Episode 1 introduction, and start with the first interviews of the series. Bonus episodes are also available, and it took a while, but Season 2 is underway...

SPYCRAFT 101 The Real Secrets of Area 51. Peter Merlin is an author, historian, freelance researcher, and writer. He also worked as historian and archivist at NASA for more than 30 years and has been researching and writing about Area 51 for many years and compiled all his knowledge in his book Dreamland: The Secret History of Area 51, a massive 560 pages work with more than 700 images. In the podcast he talks about the early beginnings of the CIA's Area 51, the development of cutting-edge aircraft technology, and some of the most iconic airplanes ever built. Peter also debunks some of the conspiracy theories. He documented Area 51 from its early beginnings, when it was little more than a dry lakebed, through its growth as CIA facility to develop and test cutting-edge aircraft technology. Great interview with new insights and facts.

Ralph Simpson on Cracking the Enigma

Ralph Simpson was speaker of the month at the California Historical Radio Society where he gave a talk on the early development of encryption devices. He focused on the Enigma cipher machine, its inventors and patents, and its use by the German military during the Second World War. He also explains why the machine was considered unbreakable, but eventually proved to be the Achilles' heel of the German armed forces during the Second World War.

Ralph had a career in the computer industry but also developed a passion for old cipher machines and their history. He is a respected member of the cryptologic history community and runs a website with a wealth of historical crypto devices and equipment for secret communications, all accompanied by technical details and relevant historical information. Be sure to visit his website Cipher History.

A Call to Former KL-7 and KL-47 Operators

TSEC/KL-7 © Dirk Rijmenants

The TSEC/KL-7 crypto machine was developed by the Army Security Agency (ASA) and Armed Forces Security Agency (AFSA) under the name AFSAM-7, and introduced in 1953 by the National Security Agency (NSA) into the U.S. Army and Air Force, and later also into the CIA and FBI. The machine also served in all NATO forces, their embassies and some state departments. The U.S. Navy AFSAM-47B, later known as the TSEC/KL-47, was compatible with the KL-7. The last machines  retired in the early 1980s. It's been little over 40 years ago that the last machines left the service and time is running out to document first-hand accounts on these machines.

If you are a retired signals veteran with experience on the KL-7 or the KL-47, as operator or technician, a member of a signals association or organization, or worked in the communications section of a state department that used the KL-7, then contact us through our website to document your story. The KL-7 is fully declassified and we're not interested in classified information, we only want to preserve the cryptologic history of these Cold War icons.

Besides the United States, the KL-7 was also used by its NATO allies Australia, Belgium, Canada, Denmark, England, France, Germany, Greece, Italy, Luxemburg, the Netherlands, Norway, New Zealand, Portugal and Turkey. Outside NATO, the KL-7 was also on loan to South Korea, South Vietnam and Taiwan. If you're a signals veteran from any of these countries, a state department or embassy in the 1950s to 1980s era, then contact us, or spread the word.

Unfortunately, time is running out to document first-hand accounts, as the people involved are age seventy or older, and memories fade. Please share this request with all signals communities that might have former KL-7 or KL-47 operators and technicians. Those who share their story retain full control over the content and how it is published.

Let's preserve cryptologic history!

Visit the U.S. TSEC/KL-7 ADONIS & POLLUX webpage to learn more about the KL-7, its development, technical details and full history, including some first-hand accounts, also shown below, to get an idea of the kind of stories we hope to document. You can contact us through the contact page on our website Cipher Machines and Cryptology.

• KL-7 in Vietnam - COMSEC Support at Air Base Saigon
• OTT Mixers and the KL-7 at NATO in West Germany
• The KL-7 on Merchant Ships during the Falklands War 
• History of the TSEC/KL-7 ADONIS & POLLUX (full history)
  

Enjoy reading!