Tim Koeth’s cryptologic hobby sits at the intersection of historical cryptography, electromechanical engineering, restoration, radio, and hands-on experimental history. It is less about modern computer cryptography than about preserving and actually operating the physical machines that implemented secure communications during the 20th century.
His interest goes back to childhood, when formerly secret cipher technology was becoming increasingly accessible to the public. Over time, that developed into collecting, studying, repairing, and operating vintage cryptologic equipment. To date, he has worked with machines associated with several different cryptographic traditions, including the German Enigma, the American SIGABA/ECM Mark II and M-209, the NATO KL-7, and the Swiss NEMA.
A particularly important part of his hobby is restoration rather than simple collecting. Tim and his friend Jim have worked with the National Cryptologic Museum at Fort Meade to return historical cipher machines to operating condition. One notable project involved making a SIGABA operational for museum display, while another SIGABA is still undergoing restoration. This requires understanding the machines as electrical and mechanical systems—rotors, stepping mechanisms, switches, wiring matrices, contacts, printers and power supplies—as well as understanding the cryptographic procedures that governed their use.
The Enigma is probably the most visible part of his cryptologic activities. Tim has access to an original three-rotor German Enigma and has used it as an operating machine rather than merely displaying it. He and friends have participated in the Maritime Radio Historical Society’s annual Crypto Transmission Event, in which authentic historical German encrypted messages are transmitted by radio and participants attempt to recover and decrypt them using period procedures. In the 2023 event documented by WIRED, as well as the 2025 event documented in TERP, Koeth and his friends received an encrypted German U-boat message and worked through the historical Enigma settings and operating procedures to decrypt it.
That activity also overlaps with another technical hobby: historical radio communications. The challenge is not simply to type ciphertext into an Enigma simulator. The message is transmitted over radio, received, transcribed, interpreted according to historical message procedures, and then processed using the cipher equipment. It effectively recreates part of a WWII communications chain using surviving technology.
There is also a strong experimental-archaeology aspect to what he does. Operating an original machine reveals practical characteristics that aren’t obvious from reading cryptographic theory: how long key changes take, how operators can make mistakes, how rotor and plugboard settings are entered, how mechanical reliability affects communications, and what daily operation of these systems was actually like. The machines become experimental apparatus for understanding the history of cryptology.
Tim’s cryptologic hobbies should be characterized as the collection, preservation, restoration, technical study, and historically authentic operation of vintage cipher and communications equipment. What distinguishes it from ordinary militaria collecting is that he wants the artifacts to work: understanding how the machine was engineered, reconstructing how an operator would have used it, and occasionally putting the entire historical communications process back into operation. As part of his personal educational mission, Tim delivered a public lecture to the Los Alamos Historical Society on the functioning of the Enigma with a live demonstration.
His fascination in collecting and working with cryptologic machines also fits closely with the broader pattern of his historical interests—the uranium-cube investigation, Atomic Age artifacts, and vintage scientific instruments. In each case, the artifact becomes the starting point for a combination of engineering investigation, archival research, restoration, and reconstruction of the historical circumstances in which the technology was actually used.