The STU-II (Standard Telephone Unit II) is a

secure telephone A secure telephone is a telephone that provides Secure voice, voice security in the form of end-to-end encryption for the telephone call, and in some cases also the mutual authentication of the call parties, protecting them against a man-in-the-mi ...

developed by the U.S.

National Security Agency The National Security Agency (NSA) is an intelligence agency of the United States Department of Defense, under the authority of the director of national intelligence (DNI). The NSA is responsible for global monitoring, collection, and proces ...

. It permitted up to six users to have secure communications, on a time-shared (e.g.: rotating) basis. It was made by ITT Defense Communications, Nutley, New Jersey. An OEM partner was

Northern Telecom Northern may refer to the following: Geography * North, a point in direction * Northern Europe, the northern part or region of Europe * Northern Highland, a region of Wisconsin, United States * Northern Province, Sri Lanka * Northern Range, a ra ...

. According to information on display in 2005 at the NSA's

National Cryptologic Museum The National Cryptologic Museum (NCM) is an American museum of cryptologic history that is affiliated with the National Security Agency (NSA). The first public museum in the U.S. Intelligence Community, NCM is located in the former Colony Sev ...

, the STU-II was in use from the 1980s to the present. It uses the

linear predictive coding Linear predictive coding (LPC) is a method used mostly in audio signal processing and speech processing for representing the spectral envelope of a digital signal of speech in compressed form, using the information of a linear predictive model ...

algorithm LPC-10 at 2.4 kilobits/second to digitize voice, and the "Key Distribution Center" (KDC) for key management. The display also stated that the STU-II B is the standard narrow band secure telephone. STU-II replaced the STU-I, KY-3 and the Navajo I. The last was a secure telephone in a briefcase, of which 110 were built in the 1980s for use by senior government officials when traveling. The Navaho I also used LPC-10. Some 10 000 STU-II units were produced.

External links

Delusion.org - National Cryptologic Museum pictures

External links

See also