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Secure voice unit - this page is a stub

NESTOR is a family of voice encryption devices, developed in the early 1960s by the US National Security Agency (NSA). Of this family, the KY-8 was the base station and vehicular unit, whilst the KY-38 was the manpack unit and the KY-28 was the airborne variant. NESTOR devices were among the first to offer real digital encryption, instead of the far less secure voice scramblers.

As NESTOR is a wideband solution, it is only suitable for radios operating above 30 MHz, typically in the VHF-L (30-88 MHz) and UHF (225-400 MHz) bands, such as the VRC-12 series that were used during the Vietnam War [1]. Such radios generally have a channel spacing of 25 or 50 kHz. The first NESTOR devices were rolled out during the Vietnam War in 1965 [2]. Several hundreds of NESTOR devices were lost to North Vietnam when the Republic of Vietnam (RVN) fell in 1975 [6].

NESTOR devices
KY-8 NESTOR voice encryptor used in base stations and vehicles
KY-28 airborne NESTOR voice encryption device
KY-38 manpack NESTOR voice encryption device
Production of NESTOR devices started in 1964 – initially in small quantities – with the first KY-8 stationary/vehicle units fielded in Vietnam in 1965. Full distribution of the KY-8 took until 1968. The KY-28 (airborne) and KY-38 (manpack) units followed in 1967, with full distribution com­ple­ted the following year [2]. Although NESTOR was successfully used in some situations, the overall experience was not very good. NSA estimates that one in ten units was actually used [5].

There were many technical issues, for example:

  • Poor voice quality
  • Radio range reduction of 10% when using encryption
  • 600 ms delay at the start of each transmission
  • KY-28 too big for some airplanes
  • KY-8 running too hot in Vietnam
  • KY-38 too heavy in the field (about 25 kg with PRC-77 radio)
In addition, there were also operational and organisational problems:

  • Lack of interconnection cables
  • Airforce uses AM, ground forces use FM
  • KEY doctrine too strict; too few radios in a single network
  • 1001 NESTOR units lost in Vietnam (mostly in downed aircraft)
  • Key renewal at 0:00 (during enemy contact), later changed to 6:00
In total, approx. 30,000 NESTOR units had been produced by 1975, around the time that NESTOR was succeeded by the VINSON wideband voice encryption system. VINSON devices were much smaller and offered improved security. KY-8 and KY-38 were suceeded by KY-57, while the airborne KY-28 was replaced by KY-58. VINSON is not compatible with NESTOR.

  1. Brooke Clarke, AN/KY-38 Secure Voice System
    Retrieved June 2015.

  2. Charles R. Meyer, Division-Level Communications, 1962-1973
    Website Vietnam Studies. Chapter VIII: Security Response. → Homepage
    Washington DC, USA, 1982. Retrieved June 2015.

  3. James Bamford, Body of Secrets
    ISBN 1407009206. 2008. pp. 352-353.
     James Bamford

  4. David G. Boak, A History of U.S. Communications Security
    Lectures, 1966. Revised July 1973. 1

  5. David G. Boak, A History of U.S. Communications, Volume II Security
    Lectures, July 1981. P age 43-46. 2

  6. Gary Bright, DON VI' 600
    Undated. 5 pages. Released by NSA in 2000. 3
     (a) Later account about Don Vi' 600 (3 pages)

  7. Wikipedia, NESTOR (encryption)
    Visited 30 April 2024.
  1. Declassified by Interagency Security Classification Appeals Panel, 14 October 2015.
    EO 13526, section 5.3(b)(3).
  2. Declassified by NSA 11 December 2008. EO 12958.
  3. Gary Bright was the US Army officer who developed the COMSEC accounting system for the South Vietnamese armed forces. This 5-page document was provided in 2000 by NSA to author James Bamford. The 3-page document listed under (a) provides additional details.

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Crypto Museum. Created: Monday 01 June 2015. Last changed: Tuesday, 30 April 2024 - 18:33 CET.
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