|TSEC/KL-7 © Dirk Rijmenants|
The TSEC/KL-7 was the first rotor cipher machine to use electronics, and although the KL-7 had excellent cryptographic properties, its track record is what made this machine a true Cold War icon. My first encounter with that curious unknown machine with vacuum tubes was back in 2005, displayed behind glass on the battleship HMS Belfast in London.
It took another six years to unravel the inner workings of this cryptologic beauty, and write the first accurate KL-7 simulator. This was only possible thanks to the release of many technical documents from the National Security Agency (NSA), through Freedom of Information Act requests (FOIA's) from Bill Neill, and published by Nick England from US Navy Radio Communications. The technical expertise from Paul Reuvers and Marc Simons from the Crypto Museum, and from George Mace, were also instrumental to develop the KL-7 simulator.
However, despite the release of some history related documents, only fragmented pieces of its development and operational use were available, and the history of the KL-7, initially named AFSAM-7, remained largely unknown to the public. In the last three years, I could connect more dots, found in the NSA's William Friedman records.
Historical records from the U.S. Army Security Agency (ASA) contained production details, planning and procurement, and later described the analysis
of the KL-7's use in Vietnam. Those records were preserved by the NSA. The NATO archives revealed the use of the KL-7 by many allied countries and some of their state departments, and the technical support they received.
Although there were only unconfirmed hints that the KL-7 was also used by the CIA and FBI, some tiny bits of information provided clues on where and how to search for more information. Moreover, ASA records confirmed the procurement for those agencies. That search took long, but eventually led to a few CIA documents and multiple FBI files that confirmed their own use of the KL-7, and its use by the White House and some Asian countries.
The KL-7 also had its own chapters in the history of Cold War espionage, with chief warrant officer John Walker selling the machine's technical details and secret keys lists to the Soviets, but the Counter Intelligence records from the Director of National Intelligence (DNI) also detailed warrant officer Joseph Helmich's betrayal, leading to other FBI files on counterintelligence operation Hookshot to catch Helmich. His case is less known than John Walker's, but just as interesting.
Ever more pieces of information were added to the KL-7 webpage, which already contained all technical information, making it quite large. To make the KL-7 history more accessible, I decided to publish the article that I started in 2022, which also includes references to the relevant ASA, AFSA, NSA, NATO, FBI, CIA and DNI files. This way, everyone can easily find all related files for their own research.
Since my motto is "history is here to share", you're free to share or publish the
below document, or parts of it, provided that proper credits are added. Why should you share it? Because its use across the world for decades, and the spy cases, make the KL-7 a true Cold War icon that deserves its place in history, but also to honor the cryptologists and engineers who developed this marvel, and the operators who served around the world, lest we forget.
If you're also interested in how the machine works, its development and full history, then visit the TSEC/KL-7 page at the website.
Call to Veterans! If you operated or maintained the KL-7, we're always interested in your experiences with the machine, to expand its history. We're not interested in classified information, only stories about where and how you worked with the KL-7 (the machine is declassified). Since the KL-7 retired 40 years ago, time is running out to preserve personal testimonies. Help us preserving history!