Sigsaly was U.S.'s ultra-secret WW II secure radiotelephone
conferencing system. This speach cyphering system was developed
by Bell Labs, the equipment manufactured by Western Electric,
and sponsored by the Army Signal Corps. Dubbed "X System"
and "Green Hornet", Sigsaly was remarkably sophisticated
and successful. The code was never broken during the war.
"It was a one time key digital encryption system built
with 1940s technology; about a dozen racks of vacuum tubes
and keys stored on phonograph records. This was used only
for rare conversations between leaders across the Atlantic.
" - John Nagel
"Bell Telephone Laboratories was to develop a telephone
scrambler that would allow Winston Churchill and President
Roosevelt to have secure conversations. Code named "Sigsaly,"
this transatlantic scrambler needed, at the London end,
not only five foot high intermediate scrambler cabinet,
but also over 30 seven foot tall relay racks weighing eighty
tons, 72 different radio frequencies, a large air-conditioned
room, and 30 kW of energy to encipher one short conversation
(The Cabinet War Rooms, Imperial War Museum, London, 1994)."
-
"It used a vocoder with 10 bands of 300 Hz, each sampled
for amplitude every 20mS; the digital signal was Vernam
encrypted (though since the samples had six levels, the
arithmetic was modulo 6). The cables from the scrambling
equipment to the users were pressurised and alarmed. Finally,
the radio link used an early spread spectrum technique to
reduce the likelihood of interception or jamming. "
- D. Kahn
The Creation of the 805th
The creation of SIGSALY was only part of the challenge required to construct
a secure worldwide voice system. A cadre of highly skilled individuals was required
to run the newly created device effectively. This requirement was fulfilled in
1942 by the formation of the 805th Signal Service Company. Their mission was
to maintain and operate the SIGSALY communications secure network between army
headquarters in Washington and overseas locations throughout the world. All personnel
were hand-picked for their special talents and qualifications; the group included
individuals with extensive backgrounds in electronics and telephony. Classes
were originally held in New York City to allow instructors from Bell Labs easy
access to the school and the students. In July 1944, both the school and the
headquarters of the 805th were moved to the Pentagon in Washington. By that time,
a total of 193 officers and men had been trained. The unit would eventually reach
a total of 356 individuals: 81 officers and 275 enlisted men. These individuals
were assigned to 12 separate detachments, each consisting of 5 officers and 10
enlisted men. Each detachment was expected to operate on a 24-hour basis. - NSA
The SIGSALY Story
