Friday, September 25, 2009

TSEC/KL-7 Simulator

I just finished and uploaded my newest cipher machine simulation. It's an accurate simulation of the TSEC/KL-7 Cipher Machine, codenamed ADONIS or POLLUX. The KL-7 was an off-line rotor cipher machine, developed in the late 1940's by the American Armed Forces Security Agency (AFSA) and introduced by the newly formed National Security Agency (NSA) in 1952. The KL-7 is one of those Cold War beauties with a remarkable history.

The new freeware KL-7 simulator provides an authentic look and feel with its hands-on approach. With all known surviving KL-7’s sanitized, stripped from all rotor and stepping unit wiring, this simulator is the only remaining way to actually work with this beautiful machine. After my Enigma, M-209 and Hagelin BC-52 sims, this new sim again gives you the chance to actually work with a famous crypto machine, and use all nuts and bolts just as an operator did on the real machine. There's even an option to rewire all rotors yourself, to individualize the machine.

Most of the men who actually worked with this machine are at least well in their sixties or seventies, and the sim is an attempt to keep the history about that magnificent machine alive. The simulator comes with a 15 page manual, including the technical details and the history of the KL-7.

Update v5.0 March 2013
: The KL-7 simulator has been updated according to recently declassified documents. Please visit this blog post for more information.

You can download the KL-7 simulator on my website and all your comments and feedback are most welcome. Enjoy it!


Ken Prescott said...


Crazy idea: how about asking the Russian Federation for info about the real KL-7 rotors & stepping? (Evil grin).

Dirk Rijmenants said...

@ Ken,

nothing crazy about that. They are perfectly able to give me all the details. However, the SVR, from all services, is the last to open their files to the public. But if they would do so, they still could not provide the wirings, that changed very often. Nonetheless a nice idea, so, to all SVR archivists that read my blog, come on with those KL-7 files! :-)

GARY said...

Hi Dirk, you have an excellent site. I served as a radio op. in the Britisah Army, regulars 1964 to 1971 and as a reservist 1972 to 1984. I alsos erved time as an EW (now called ECM) operator mainly in West Germany. As I speak German my duties were chiefly monitoring NVA-DDR or GT (Border Guard) transmissions. Recorded a lot as well if I remember correctly. You are correct about the new openess with which Warsaw Oact guys now talk. I have contacts in the NVA Forum who served as Army, Border Guard and STASI (HAIII) operators.Very interesting guys who have have answered many questions. My only code use was the low level Slidex, and duriung COMCEN work we frequently saw, but NEVER touched the ALVIS and BID crypto machines. ALVIS was LARKSPUR era, and BID I seem to recall came in with the BRUIN system. Graet site,buddy, keep her rolling, 73 de Gary

Anonymous said...

it is useful. thanks.

Anonymous said...


The version of the machine I have decrypts what has been encrypted as 'Z' and 'J' as spaces. Should this be?


:: Jim::

Dirk Rijmenants said...

Hi Jim,

Visit my website for more info or contact me by e-mail.

Anonymous said...

I used KL7 frequently during my 30 years at sea between 1963 and 1993 although the last one I worked with I had to destroy in 1984. The flaw in the KL7 was when encrypting the letter J it would always decrypt as Y. Similarly encrypting letter Z would always decrypt as X.

Lovely machine to use.