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Willliam Friedman Publishes "The Index of Coincidence Method of Code-Breaking"

1922
<p>These publications were not available to the public at the time of issue. The English version predated the French, though the French edition was falsely dated the year earlier.</p>

These publications were not available to the public at the time of issue. The English version predated the French, though the French edition was falsely dated the year earlier.

In 1922 U.S. Army cryptologist William F. Friedman published The Index of Coincidence and its Applications in Cryptography, Department of Ciphers. Publ 22. Geneva, Illinois, USA: Riverbank Laboratories.

Friedman's report presented the coincidence counting, or index of coincidence method of code-breaking.

This work appeared in 1922, and antedated the French translation noted below which was falsely dated 1921. Shulman, An Annotated Bibliography of Cryptography, 1976, pp 84-5 noted that the French translation was by General Cartier, and that both editions were printed in Paris by Col. Fabyan as anonymous publications. 

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