The Scandalous History of the Last Rotor Cipher Machine
t-3 writes:
https://spectrum.ieee.org/the-scandalous-history-of-the-last-rotor-cipher-machine
If you've never heard of the HX-63 until just now, don't feel bad. 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 10600 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.
Just as worrisome was that CAG was a privately owned Swiss company, selling to any government, business, or individual. At the NSA, Friedman's job was to ensure that the U.S. government had access to the sensitive, encrypted communications of all governments and threats worldwide. But traffic encrypted by the HX-63 would be unbreakable.
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