The literature of CRYPTOGRAPHY has a curious history. Secrecy, of course, has always played a central
role, but until the First World War, important developments appeared in print in a more or less
timely fashion and the field moved forward in much the same way as other specialized disciplines.
As late as 1918, one of the most influential cryptanalytic papers of the twentieth century, William F.
Friedman’s monograph The Index of Coincidence and Its Applications in CRYPTOGRAPHY, appeared as
a research report of the private Riverbank Laboratories [577]. And this, despite the fact that the work
had been done as part of the war effort. In the same year Edward H. Hebern of Oakland, California
filed the first patent for a rotor machine [710], the device destined to be a mainstay of military
CRYPTOGRAPHY for nearly 50 years.
