Regarding the question of how far back TEMPEST goes, I took a look at
David Kahn's "The Codebreakers" which was copyrighted in 1967.
TEMPEST is not listed in the index. However I did find the following
paragraph in a portion of the chapter on N.S.A. that discusses
efforts to improve the US State Department's communications security
(p. 714):
"... the department budgeted $221,400 in 1964 for 650 KW-7's. ... The
per-item cost of $4,500 may be due in part to refinements to prevent
inductive or galvanic interaction between the key pulses and the
plaintext pulses, which wire tappers could detect in the line pulse
and use to break the unbreakable system through its back door. "
This would be the electro-mechanical equivalent of TEMPEST and
suggests that NSA was well aware of the compromising potential of
incidental emanations long before the computer communications era.
Another useful data point would be earliest reports about the BBC's
system for detecting unlicensed television receivers. That system
used vans equipped to detect a TV's local oscillator, but may well be
an offshoot of emanations intelligence research.
Arnold Reinhold
