A rotor for an electromechanical cipher machine developed by the USSR after World War II for use by the military and intelligence services. Based on the German Enigma machine, the Fialka used a series of rotors positioned on a common axis. Each rotor had electrical contacts on both sides, with each contact corresponding to a letter of the alphabet. The contact associated with a certain letter on one side of the rotor was connected by internal wiring to a contact on the other side for a different letter, thus scrambling the letter. For the Fialka, ten rotors were stacked side-by-side with the contacts of one touching those of its neighbor. The resulting electrical circuit passed through the entire set of rotors, in effect scrambling the original letter multiple times (Reuvers 2025a). In addition, the Fialka had an interchangeable punch card that acted like an eleventh rotor (Reuvers 2025b). The card was exchanged daily for a card with a different set of punched holes.

Rotor-based cipher machines were invented in 1915 by two Dutch Navy officers: Theo van Hengel and R.P.C. Spengler. Until recently, others received credit for the invention, a story that illustrates how the patent system can be misused. The complex and unfortunate history is untangled in a 2003 paper by Karl de Leeuw (de Leeuw 2003).