spartans_in_darkness

.GA
"FOP SEeRHOeOMlrHmt1
EO 1.4. (c)
(S//SI) The Communists' Big
Communications Change, April 1962
American capabilities against their communications.
Realizing just how vulnerable their communications
were caused the VC to. make the
changes. NSA also charged that this problem of
compromising SIGINT information by the South
Vietnamese was historic and endemic.. The
Americans could cite specific instances in theprevious
six months in which the government in
Saigon had deliberately leaked SIGINT informa~
tion for political purposes.1
(Te//e{) The next night the roof fell in on
Allied SIGINT operations in South Vietnam when
the Viet Cong executed a major, nearly total communications
and cryptographic change on their
military and political-military networks. The
changes effected by the communists were deep
and pervasive. As a DIRNSA-directed report
issued two weeks later would state:
Recent changes in Viet Cong Communications
procedures have resulted in increased transmission
security by [the] introduction of tenday
changing callsigns, frequencies, and schedules
coupled with [a] standardization of traffic
format so that not only do Viet Cong messages
throughout all of South Vietnam resemble each
other but they also resemble those of the
DRV. 1l 5
('fSl/S!) On April 20, the news of the VC SOl
change was reported to the secretary of defense,
the United States Intelligence Board, the Defense
Intelligence Agency (DIA), and the assistant chief
of staff for intelligence of the JCS. The USIB was
briefed personally by Admiral Frost on the situation.
The board was asked to consider more stringent
rules covering the release of technical SIG­
INT information to the ARVN, as well as the
urgent need to establish a U.S.-only, or no foreign
national (NOFORN) site. The USIB, in turn,
asked its SIGINT Committee, chaired by the former
DIRNSA, General Samford, to study NSA's
recommendations.
(el/eO That NSA, in the first place, would
think that the VCcould work out such a complete
changeover within a day of the supposed "leak" of
the report strains all logic. This is especially so
when one considers the requirements for such a
Page 146
"FOP SEeRHh'eOMINTh'Xl
OGA