Cryptographic Tool Challenge
We will be posting "tools of the cryptologic trade" periodically on this link. All visitors are invited to provide any information on how the tool was used by cryptographers. A summary of information received will be posted under the article. Please submit your unclassified, non-target specific comments to ncmfweb@aol.com, with a subject line of: Cryptographic Tool Challenge -- Attn: Dave D'Auria.
A World War II Slidex
The artifact pictured below is believed to be a WW II era Slidex code device. A Slidex is a manual encoding system used mainly for tactical communications to provide a short-term level of security when non-secure communication links are being used. They use a word or sometimes phrase substitution based upon a prearranged set of codewords or codephrases. The device pictured below came from the Lou Kruh collection donated to the NCM in April, 2010. It is about 8inches long by 4 inches wide. A wheel on the side rotates (i.e., "slides") the list of codewords forward or backward to encrypt usually short stereotyped messages. We are looking for information from any of our website visitors who may know who, how, when and where this device was actually used by cryptographers and/or radio operatiors.
The 10 Point Divider
The 10 Point Divider (sometimes called an 11 Point Divider) pictured below came from the estate of a now deceased former cryptographer. In the public sector this "tool" is commonly used in drafting, form and textile design, model design, long range navigation, etc. We're looking for information from any of our web visitors who may know how this tool was used by cryptographers.
Comment by George on 5/16/10
The divider, and others like it (I have one) were used to manually transcribe data (1's and 0's) from analog displays and was used by both signals analysts (to find structure) and cryptanalysts (to obtain cipher). Time base jitter was a common problem and the higher the data rate, the more uncertain one was of the integrity of the stream. Use of these dividers often meant the difference between "no cipher" and "some cipher" until a system could be devised to automatically digitize the data.
Comment by Frank on 7/13/10
I used the 10 point divider in the 1960's in a signal analysis application to determine
presence of and to measure cyclic activity on continuous paper sonogram
displays. The 10 point divider came in different sizes from about 8 inches
in length to about 12 inches. In later years it became a handy tool to lay
out distances to scale on maps. This instrument may still be on display in a
corridor display case on the fifth floor on building 2A.
