The TSEC/KL-7 is an American off-line non-reciprocal rotor cipher machine, introduced by the National Security Agency (NSA) in 1952. It was the first tactical lightweight electronic (vacuum tubes) crypto machine, specially developed as a standard crypto device for all parts of the U.S. armed forces. The machine was widely used by the U.S. and several of its NATO partners until the mid 1960's, and served later on as backup, often superenciphered on other systems, until its withdrawal from service in 1983.
In the 1950's, the machine was a marvel of technology that combined the latest cryptologic knowledge and electronics in a machine that weighs a mere 20.5 lbs (9,3 Kg). Its cleverly designed keyboard, with a sliding permuter board, replaced the complex and large switch, usually required to change the signal direction through the rotor pack. Special interchangeable plastic notched rings were placed on the KL-7's scrambling rotors to control the rotor movement in a most complex fashion. Vacuum tubes controlled the timing signals of the newly designed miniature printer system. The machine was introduced under the name AFSAM-7, but had its name changed to TSEC-KL-7 in the early 1960's.
The machine had excellent cryptographic properties and was designed to resist any cryptanalytic attack by the Soviets in the 1950's and early 1960's, even if its technical details would have been compromised. Unfortunately, in 1967, Chief Warrent Officer John Walker not only compromised the KL-7 design by selling the complete technical manual to the Soviets, but also provided them with the key lists for many years. Walker's treason added even more to the Cold War myth that surrounded this machine for decades. The KL-7's history and technical specifications were kept secret for decades and information about the machine only gradually surfaced in recent years. This page is a tribute to the finest ASA and AFSA engineers and cryptologist who designed the KL-7, and to the men who worked with this beautiful machine while serving their country in all corners of the world
For those interested in these historical Crypto machines, I do have five caches using them. In order of easy to more difficult; "Hagelin" BC-52 Cipher Machine, "Hagelin" M-209 Field Encryption Machine, "ADONIS & POLLUX" TSEC/KL-7 Crypto Machine, "Purple" aka 97-shiki ōbun inji-ki, and Belle Isle Marsh Enigma
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You can validate your puzzle solution with certitude.