"Arnold G. Reinhold" <[EMAIL PROTECTED]>:
quoting David Kahn's "The Codebreakers" (1967):
> "... 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.
This seems to refer to the problem of sending key and/or plaintext
alomg the communications channel intended to carry only ciphertext.
I seem to remember reading that this allowed allied reading of East German
cable messages tapped in the 1950s (operation Prince ? Karlshorst tunnel ?).
A quick web search turns up this, which may be what I'm thinking of.
http://www.fas.org/irp/facility/cia_germany.htm
--
##############################################################
# Antonomasia [EMAIL PROTECTED] #
# See http://www.notatla.demon.co.uk/ #
##############################################################
