spartans_in_darkness

'EO 1.4. (c)
TO~ SEeRETHeOMII4Th'X1
tled for the general use of codebooks with an
accompanying encipherrnent system which used
random, digital keyl I
I
'-- ----1- lFurther adjustments
agreed to in Hanoi included shrinking the
size of cryptonets, that is, reducing the number of
radio stations in a group using the same cryptographic
system, and then using special and
mnemonic codes as backups when the main systems
were compromised, or otherwise could not
be used. 12 3
(TS//SI) The implementation of this general
upgrade resulted in a sort of "rolling tide" communications
change, which flowed outwards
from Hanoi to communist elements in Laos and
South Vietnam. By April 1962, its waves had
reached the furthermost beaches and coves of the
southern insurgency. The results were almost catastrophic
for the American SIGINT effort. Davis
Station (as Tan Son Nhut had been renamed) was
caught in the midst of its first replacement cycle
and, as a result, its technical expertise was severely
curtailed. The station was responsible for fifty
to fifty-five VC transmitters and yet its analytic,
DjF, and RFP sections were unprepared for the
change. 12 4
The ASA site at Bien Hoa was able to
make progress on some recovery in the Nam Bo
region, but communist communications in the
MR V region were almost completely lost for the
time being. 12 5
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