Major Update of the U.S. KL-7 Simulator

KL-7 Sim Version 5.0

It's been more than three years now since I  released my TSEC/KL-7 simulator. Today, this crypto machine simulation is definitely my favorite. Not in the least because I had to start from scratch, both historically and technically, when I decided to develop this KL-7 sim.

Last year, Uri Blumenthal from MIT proposed to develop a JAVA version of my KL-7 simulator. His version was  finished and published three months ago. However, since 2011, new information had been declassified, making an even more accurate simulation possible and providing new information to add to the historical sections of the sim's manual.

If it wasn't for Uri, I had never embarked on this new and sleep-depriving project to update the KL-7 sim. He wanted to adapt his JAVA version according to the latest info and insisted not only that I updated my simulation, but also to make both sims fully interoperable. Of course, cryptographically, both sims were already compatible, but they now have the same key file format, they offer similar software nuts and bolts and the encryption procedures are on par.

We now both published our version 5.0, which is as complete and accurate as it can get. Here's a list of changes, applied on version 5.0 of the KL-7 Simulator:

• Renaming of rotor assembly parts and other components according to the real KL-7 manual
• Notch rings now set relative to the alphabet ring by letters, instead of against the core by numbers
• Added a 13th rotor, introduced in 1975
• All rotor cores interchangeable, also for the fourth rotor, which has to be equipped with a special "wide ring"
• Re-wrote  the encryption procedures according to the declassified KAO-41C/TSEC, corrected key sheet examples and revised the technical and historical sections of the manual.
• Saving and opening of key files in .txt file format *
• Set Mode for quick and easy adjusting of the rotor alignment (start position of the rotors) *
• A software zeroize button *
• Switching between letters and figures with either arrows Up and Down or the SHIFT *

* Not available on the real KL-7 machine.

The KL-7 simulator is an historical reference to a magnificent crypto machine and it's fun to use! The 20 page manual shows how to work with the simulator, how to encrypt messages, exciting example training messages straight from the Cuban missile crisis, the technical details, history on the development and use of the machine and, as such a notorious machine deserves, fascinating spy stories involving the KL-7.

My first acquaintance with the KL-7 was years ago, on the battleship HMS Belfast in London, where it was displayed behind glass. For decades, this Cold War cryptologic beauty, developed by ASA and AFSA, and introduced by NSA in 1953, remained hidden under a veil of secrecy and there were no historical, scientific or technical publications whatsoever to start from. It's been quite an interesting journey before arriving at today's new version.

The project was one of evolution and a few updates, since we always strive to provide the most accurate historical and technical information. That's what makes the difference between a toy and a truthful simulation. The previous version, published in March 2011, finally worked as it should, at least when it came to machine output and graphics.

However, some details, names and procedures were still unknown. Also, the KL-7 sim's nuts and bolts were operated in exactly the same way as the real machine, and that's not really the impatient software user's cup of tea. A returning question was why it is so elaborate to work with these crypto simulations. Of course, the reason is that the software works exactly like the real thing. Otherwise, it wasn't a simulation. Version 5.0 meets those requests and has some extra features the KL7 that operators back then would have loved on their machine.

The KL-7 simulator for Windows and JAVA KL-7 are available for download on Cipher Machines and Cryptology and since history is there to share, it's freeware, as usual. Please read the readme.txt file in the download Zip before installing the software. Any previous version should be uninstalled first via the Windows Configuration Screen.