This work is licensed under aCreative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
The material described on these pages is created, collected, edited and published
by Frode Weierud, © September 2023
| Rotor Machines and Wired Wheels |
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This space is dedicated to historical research into cipher machines using wired wheels, also called rotors, but which I now like to call permutation wheels. Here we will also look closer at the wheels themselves, their development and properties. The terminology can sometimes be confusing, especially because the usage varies among the different users and authors. Rotors was originally an American term, while the British preferred the more descriptive wired wheels. The reason being that anything that rotates can be described as a rotor. However, for many of us a rotor means the rotating part of an electrical motor and as such it is understood to contain some electrical wiring. This is of course also the case for the rotors used in cipher machines. Unfortunately, many cipher machine also use wheels which do not use electrical connections but instead are equipped with protrusions, pins or lugs that are either fixed or can be varied at will. And here the unfortunate happens, some writers call also these mechanical wheels for rotors, and then the confusion is created of what is a rotor and a rotor machine.
It should be made clear that a rotor machine is a cipher machine using wired wheels for the enciphering function. Cipher machines using wheels with pins or lugs belong to the category of machines with mechanical key generators, even if many of these machines will have electrical motors or other electrical functions such as we find in teleprinter cipher machines. However, we have some rare cases of rotor machines that use wheels with a similar permutation function to wired wheels without being electrical. These machines are either of a pneumatic or hydraulic nature using wheels with pneumatic or hydraulic channels to create the permutation function. To include also these machines the term permutation wheels therefore is more inclusive than the term wired wheels, while it at the same time is explicit in describing their function.
The treatment of rotor machines and permutation wheels that you will find below should be seen more as research notes than final articles. It is largely a collection of archive documents, notes and investigation based on the presented documents and private communications with cryptographers and other experts over great many years. The access to documents in this field is a long and very slow process, involving painstaking research in national and private archives, and FOIA requests to the various holding agencies.
At a conference of cipher machine, with a focus on rotor machines, held at the US Navy's signal intelligence branch OP-20-G in March 1945, an overview of machines they were analysing was presented.
The Enigma is such a historically important rotor machine that it has its own Web space, which you can consult here.
The British rotor machine Typex, which is an adaption and further development of the Enigma machine, is well described by the Crypto Museum: Typex — Wheel-based cipher machine. Here we will only present some archive documents and other details that is generally less well known. The Typex files are here.
The Combined Cipher Machine (CCM) was created by modifying the British Typex and the US SIGABA machines to allow them to work together. The aim was to provide high-level protection of the UK-US naval wireless traffic, which was important for the continued battle in the Atlantic. After the war, the CCM was supplied to many NATO countries for their intercommunication.
The rotor machine HX-63 developed and manufactured by Boris Hagelin through his Swiss based firm Crypto AG, is a postwar machine incorporating several novel cryptological functions, one, the rotor re-entry principle and which Hagelin patented in January 1953, was a secret crypto function used in US and British rotor machines of this period. The machine is very well described by the Crypto Museum: HX63 — Offline rotor cipher machine. However, there are development details and other documents that we should like to present and which we hope will give a more nuanced view of this machine, which like many of these devices was not one machine but rather a series of models adapted to users and demands throughout its development history. This is a characteristic of commercial cipher machine development, which generally is more market oriented than the national and military service developments. You find the HR/HX-series machines here.
Copyright:
This work is licensed under a
Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
The material described on these pages is created, collected, edited and published
by Frode Weierud, © September 2023
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