How this gadget figured in the shady Rubicon spy case //

In 1976, during a visit to the Polish Army Museum in Warsaw, I saw an Enigma, the famous German World War II cipher machine. I was fascinated. Some years later, I had the good fortune of visiting the huge headquarters of the cipher machine company Crypto AG (CAG), in Steinhausen, Switzerland, and befriending a high-level cryptographer there. My friend gave me an internal history of the company written by its founder, Boris Hagelin. It mentioned a 1963 cipher machine, the HX-63.

Like the Enigma, the HX-63 was an electromechanical cipher system known as a rotor machine. It was the only electromechanical rotor machine ever built by CAG, and it was much more advanced and secure than even the famous Enigmas. In fact, it was arguably the most secure rotor machine ever built. I longed to get my hands on one, but I doubted I ever would. //

Most professional cryptographers have never heard of it. Yet it was so secure that its invention alarmed William Friedman, one of the greatest cryptanalysts ever and, in the early 1950s, the first chief cryptologist of the U.S. National Security Agency (NSA). After reading a 1957 Hagelin patent (more on that later), Friedman realized that the HX-63, then under development, was, if anything, more secure than the NSA's own KL-7, then considered unbreakable. During the Cold War, the NSA built thousands of KL-7s, which were used by every U.S. military, diplomatic, and intelligence agency from 1952 to 1968.

The reasons for Friedman's anxiety are easy enough to understand. The HX-63 had about 10^600 possible key combinations; in modern terms, that's equivalent to a 2,000-bit binary key. For comparison, the Advanced Encryption Standard, which is used today to protect sensitive information in government, banking, and many other sectors, typically uses a 128- or a 256-bit key.