A History of US Communications Security

[furrbear]

Freshly declassified and a rather interesting read:

A History of U.S. Communications Security (Volumes I and II, 1973)
David G. Boak Lectures, National Security Agency (NSA)

http://www.governmentattic.org/2docs/Hist_US_COMSEC_Boak_NSA_1973.pdf

(From Bruce Schneier/Governmentattic)