HC-9 Transvertex

This copy was derived from E-bay from two different HC-9 auctions.

"The HC-9 was a mechanical cipher device manufactured by the Swedish company AB Transvertex. It was  designed in the early 1950's for the Swedish Armed Forces and likely remained in use up to the 1970s. This  machine was used for low-level communications such as platoon, company, up to battalion levels and in regimental and brigade staffs. The HC-9 made use of punched cards instead of the pin-wheel mechanisms of other machines (for example, the Hagelin M-209).

It is of some interest in that, although it operates by a completely different principle, it and the original version of the Hagelin lug and pin machine are the only secure modern cipher machines that are both very compact and of all-mechanical construction.

It behaves as if it contained five pinwheels, of sizes 29, 31, 33, 34, and 35. Each "pinwheel" advances one space for every letter enciphered, and their outputs are used to select one of sixteen cipher alphabets as follows: four bits are formed from the five bits presented by the five sequences by taking the XOR of each pair of adjacent bits.

This result is treated as a four-bit number. Thus, the XOR of the bits from the 29-bit and 31-bit sequences controls displacing the list of alphabets by eight places. But instead of pinwheels, the sequences are supplied by a punched card, which sits in the device and whose large round holes are sensed by little metal fingers inside the device. Another replaceable card inside the device gives the sixteen alphabets in use. These alphabets were all chosen to be reciprocal in practice for ease of use.

See pages 251-265 in CRYPTOLOGIA Volume XIII Number 3, July 1989 for a detailed article on the HC-9 by C.A. Deavours and Louis Kruh".

The HC-9 is a post World War 2 mechanical enciphering/deciphering device manufactured by A B Transvertex in Sweden. (Photo by  Michael Smith . E-mail: msmith(at)thylacine.demon.co.uk)

Rear view
Coding wheel mechanism. 
Right side view
With carrying case.
All photos in this table via E-bay
For more informatiuon on the HC-9, please view the web document developed by Paul Reuvers.

Contributors and Credits:

1) Paul Reuvers <paul(at)xat.nl>

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Mar 10/12