The HX-63 was an electromechanical rotor-based cipher machine, introduced in 1964 by Crypto AG in Zug (Switzerland). It features nine electrically wired permutations wheels, or rotors, that have more contacts than the 26 letters of the alphabet. The machine could be set up in around 10^600 different configurations. Only twelve of these machines were manufactured.
In 1963, the Swiss cryptographer Boris Hagelin created a machine so frightening in its potential to keep secrets that it ironically gave rise to one of the biggest espionage coups of the Cold War.
Hagelin’s machine, the HX-63, was a groundbreaking cipher system used to send secret messages encrypted in a way that was virtually unbreakable — even by today’s standards.
The impenetrable nature of the machine’s encryption troubled William Friedman who was both the chief code breaker for the NSA as well as a good friend of Hagelin. Friedman knew that if the HX-63 was widely adopted, the United States government would lose its capability to decipher the secret communications of other governments.
When encrypting or decrypting a message, the HX-63 prints both the original and the encrypted message on paper tape. The blue wheel is made of an absorbent foam that soaks up ink and applies it to the embossed print wheels.
After unsuccessfully imploring his friend to abandon the machine altogether, Friedman settled for a “gentleman’s agreement” whereby Hagelin’s company, Crypto AG, would not sell the HX-63 to certain countries. Their cooperation would ultimately lead the CIA to secretly acquire Crypto AG and rig its machines to spy on both allies and enemies for the next four decades.
The spying operation, which was only recently uncovered, was investigated and reported on in a stunning account by the Washington Post.
However, the unbreakable encryption machine itself was seemingly lost to history. That was until cryptography researcher Jon D. Paul discovered a HX-63 collecting dust in the basement of a French military command base. Jon tells the tale of the machine’s significance and his restoration of it in a story that I photographed for IEEE Spectrum.