Shhh! The Green Hornet

Cryptologia, Apr 2000 by Kruh, Louis

SHHH! THE GREEN HORNET

Mehl, Donald E. The Green Hornet: America's Unbreakable Code for Secret Telephony: The Untold Story of World War II, The U. S. Army Signal Corps SIGALY System. D. E. Mehl. 11605 Minor Drive, Kansas City MO 64114-5618 USA. 1997. 204 pp. $55.00.

One of the closest guarded secrets of World War II was a secret communications system known in the Signal Corps as Sigsaly and nicknamed The Green Hornet, after a popular radio program introduced by a similar sounding buzz. It was called Project X by Bell Laboratories which invented it and the "X" System by the Army General Staff.

The reason for the post-war secrecy was that it used a new digital technology that made it absolutely unbreakable by an enemy. It was used for telephone conversations between Prime Minister Churchill and President Roosevelt and by the highest levels of military and civilian officials for strategic and tactical conferences between Washington and all theaters of the war. During the war it was installed and operated by the 805th Signal Service Company (SSC).

Details of Sigsaly were kept secret until released under the Freedom of Information Act in 1975. With the release of Bell Laboratories patents and other information through the years, its contribution to the war effort became declassified. Now, for the first time, the story of this important wartime facility is told in its entirety from its inception to its final decommissioning. The author, an officer in the 805th SSC stationed in the Pentagon and at the Manila terminals of the system, tells the complete story of the development, implementation and operation of this secret telephone system and the events surrounding its use.

Mehl describes the problems and technology involved in providing secure communications and discusses some fundamental cryptography and the use of enciphering for insight to the process of making telephone messages secure; the history and processes of the design and development of the Sigaly system and why the use of a new, unproved technology was deemed necessary; and the process of obtaining approval for the acceptance and deployment of the system in both the U. S. and U. K. A diplomatic flap arose when Alan Turing, a U. K., expert was denied clearance to visit Bell Labs to examine and discuss the new super secret telephone system. The issue was finally resolved at the level of the Secretary of War, Henry Stimson. Also discussed are the recruitment and training of the skilled technical and management personnel necessary to install and operate the worldwide system with examples of some of the actual uses of Sigsaly.

Told in the context of the war, Mehl refers to Pearl Harbor, Midway, Purple, Bletchley Park and Enigma, the Bell Laboratories School for War Training, and he describes SIGTOT, the secret teletype conferencing system, which was another responsibility of the 805th SSC.

The book is a marvelously detailed look at a little known aspect of WW II cryptologic history, with 28 illustrations and drawings and copies of many memoranda and other documents.

P. S. Is it more than a coincidence that the SSC has the same number, 805, as the U. S. Army's MOS (Military Occupational Specialty) for cryptographer?