This cipher device was used by the Ministry of the Interior of Denmark to secure its communications from at least 1910 to 1914. although the device itself may be older.

The device is quite flexible and allows for frequent changes of settings. Individual letters are inscribed on ivory tiles which may be removed and easily rescrambled around the central disk. There is no surviving User's Manual, however the Danish Ministry probably issued an accompanying  chart listing the letter arrangements and changes for a stated period. These could be changed daily, weekly or monthly.

The cryptographic principles embodied in this device date back to the 15th century. In 1466, Leon Battista, an Italian scholar, wrote an essay in which he laid out the principles of polyalphabetic substitution These principles may be centuries old but they have been used in a number of modern U.S. cryptosecurity devices.

This cipher disk is a gift from the government of Denmark.

An NCM exhibit.  (Photo by Ralph Simpson)

Contributors and Credits:

1) Ralph Simpson <ralphenator(at)gmail.com>
2) NCM placard

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Apr 21/12