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Voice scrambler handset

KY-189 was a voice scrambler for tactical military use, developed by Napco International in South Hopkins (Minesota, USA) around 1990. 1 The device is housed in a ruggedised military handset and is suitable for connection to the audio socket of a range of military radio sets, such as the AN/PRC-77, the AN/VRC-12 the PRC-1077, GRC-160, VRC-64 and many other VHF/UHF narrow­band and wideband radios. One of its first uses was in the Yugoslav Wars (1991-2001) [3][4].

The KY-189 contains a microprocessor-based voice scrambling circuit, with pseudo random rolling code, combined with random timing, audio frequency shift and synchronisation.

The unit is housed in a small plastic enclosure, very similar to a standard military handset, but thicker at the microphone end. On the inner side is a 15-button keypad and a large red indicator. Microphone, speaker and Push-To-Talk button (PTT) are at their normal positions. KY-189 was originally powered by a standard 9V battery that was fitted in the large black blob at the bottom.
KY-189 scrambler handset

Later versions could also be powered directly from the radio to which it was connected [2], but in most cases the radio had to be modified for that. The version featured on this page, was adapted for the Yugoslav RUP-12 and RU-2 military radios (which had to be modified for the KY-189).

Acording to the manufacturer, the KY-189 offers more than 100 million user-programmable security codes and the built-in key generator has a cipher period of 84 x 109 years. Each time the Push-To-Talk (PTT) switch is pressed, the code changes to a new pseudo-random code.

It also features Automatic Number Identification (ANI), Status and Location Report, All Stations Alert Tone, a programmable Time-out Timer and Selective Call. Each KY-189 has a built-in unique Master Code Key, used for joint network operation and preventing unauthorised use [1].
Operating the PTT

In 1994, KY-189 was in use with US Armed forces, for use with the AN/PRC-77 and PRC-1077 radios, by the Croatian Army and by several (undisclosed) government customers [2]. Although the device provided reasonable security for tactical applications at the time, the use of a voice scrambler in general, no matter how complex, should never be considered secure. With wave-pattern analyzing techniques, often software based, they can be broken in (near) realtime.

  1. This is a rough estimation, based on the fact that the device appears first in Jane's Military Communications catalogue of 1994 [2] and the fact that it was first used in the Yugoslav Wars in 1991 [3].

KY-189 scrambler handset KY-189 scrambler handset KY-189 scrambler handset Big red LED Keypad Operating the PTT Reverse side Side view
The image below shows to position of the controls and features of the KY-189. The unit has the same shape as a standard military handset, making it very easy to substiture existing handsets for KY-189 units. The unit is controlled via the 15-button keypad at the center. At the left is the Push-To-Talk (PTT) switch. At the right is a metal clip that allows the handset to be affixed temprarily to, say, the uniform. At the bottom is the coiled cable with a radio plug at the end.

The large red LED provides visual feedback when in secure or clear mode. The keypad is used to enter the required encryption key, but can also be used to send map references, code words and status reports to the base station silently. Radio checks can be performed without speech [2].

Yugoslav Wars
When the Yugoslav Wars broke out in 1991, the KY-189 was just being rolled out in the Croatian Army. Approx. 50 units had been distributed when the hostilities started and it is believed that no further units were delivered after that [3]. Although the KY-189 provided reasonable security for tactical communication at the time, it was known by the Yugoslav Army to be breakable, which is why the latter swapped most of its KzU-61 voice scramblers for digital KzU-63 encryption units.

 Yugoslav encryption devices

Getting access to the interior of the KY-189 is rather simple. The large black 'blob' below the microphone, normally houses a 9V battery. It can be accessed by removing 4 bolts from the bottom panel. In the version shown here, the battery compartment is present but unused.

The reason for this is that in this case the KY-189 was powered by the radio to which it was connected. The battery compartment itself can be removed by releasing two recessed bolts, after which a small adapter board is revealed.

The actual voice scrambler is hidden behind the keypad and can be accessed by releasing the 6 bolts around the edges of the keypad frame. This reveals a sandwich of two small PCBs that are connected to the wiring of the handset via 2 connectors (a 7-pin and a 4-pin one) at the rear. The PCBs are not bolted or affixed in any way.
PCB sandwich removed from the handset

The upper board (i.e. the one facing the outside) contains the actual switches of the keypad and is slightly larger than the other one. The two PCBs are held together by means of three inter-board connectors, and can be separated easily by pulling them apart. Although the text has been removed from all ICs, the upper board seems to contain the digital parts, whilst the other one holds most of the analogue stuff. The rear board is much thinner and is bended somewhat.

The reason for removing the text from the ICs is arbitrary. Some manufacturers did this because they didn't want to 'educate' the competition, but in many cases it is possible to identify the components simply by looking at the layout of the PCB and the rest of the circuitry. A truely interested competitor could also x-ray the components and easily identify them that way.

The KY-189 seems to be designed as a low-cost alternative to the high-end external voice scramblers that were available at the time, possibly as a commercial off-the-shelf (COTS) product. It is built from low-cost commercial-grade components and is housed in a relatively simple enclosure with no special parts or board retainers. Yet, it complied with the usual military specifications [2] and had the advantage of being fully self-contained and easy to implement.

Battery compartment opened Battery compartment removed Small adapter board Keypad removed PCB sandwich removed from the handset PCBs removed from the handset PCB sandwich seen from the top The two PCBs separated
When looking at the exterior of the KY-189, one can't help but notice the striking resemblance to the DSP-9000 that was manufactured by Technical Communications Corporation (TCC) in Concord (Massachusetts, USA) around the same time (1992) [2]. It is housed in a nearly identical case, with the main visible difference being two extra rows of keys in place of large red indicator.

Furthermore, the DSP-9000 has a large toggle switch at the right, to select between secure and clear modes, but apart from that the housing is nearly identical to the one of the KY-189.

The specifications of the DSP-9000 are also similar to those of he KY-189 [2], but TCC, the manufacturer of the DSP-9000, is somewhat vague about the technology that is used. Whilst their website and brochure suggests that it offers real encryption, the fact that it performs (proprietary) operations in the audio time and frequency domain suggests that, no matter how advanced, it is in fact a voice scrambler.
Currently the only image of the DSP-9000 that is publicly available. Copyright TCC [5].

Although the KY-189 is no longer available from Napco, the DSP-9000 was still available from TCC in 2015, as a base station (DSP-9000), as a handset (DSP-9000 HS) and as an OEM implant board. According to their website, the DSP-9000 is interoperable with the HSE-6000 headset [5].

The KY-189 has a fixed coiled cable with an audio connector at the end. The unit is powered by the device to which it is connected, which means that a suitable voltage must be present on one of the pins of the connector. The KY-189 was adapted for various radios, simple by suppling it with the appropriate plug at the end of the coiled cable. The following connections are known:

US variant
Most Amerian radios have a 5-pin or 6-pin U-229 socket for connection of the handset. If the 6-pin variant was used, the radio could be modified for use with the KY-189. In that case, +12V had to be supplied to the centre pin (F) [2]. In all other cases, an internal battery was needed.

  1. GND
  2. Speaker
  3. PTT
  4. Microphone
  5. 12V
Yugoslav variant
The KY-189 was used in combination with various Yugoslav radio sets, such as the RUP-12 and the RU-2, both of which featured the same 7-pin audio socket. As no power supply is normally available on this connector, the radios had to be modified for this (+12V on pin 5).

  1. GND
  2. PTT
  3. Microphone
  4. 12V
  5. Speaker
  6. GND (or not connected)
Connector for Yugoslav RUP-12 or RU-2 radio
Radio sets
The KY-189 is compatible with (or could be modified for) many radios, including:

  • AN/PRC-77
  • AN/VRC-12
  • PRC-1077
  • GRC-160
  • VRC-64
  • RUP-12
  • RU-2
  1. NAPCO, KY-189 Secure Intelligence Handset
    Website, snapshot 9 July 2004. Retrieved via Wayback machine, May 2015.

  2. Jane's Military Communications, KY-189 Secure Intelligence Handset
    Fifteenth Edition 1994-1995. p. 562.

  3. Anonymous eyewitness, Croatian war against Serbia, August 1995
    Personal correspondence, May 2015.

  4. Wikipedia, Yugoslav Wars
    Retrieved April 2015.

  5. TCC, Military Secure Radio Encryption System
    Retrieved May 2015.
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Crypto Museum. Last changed: Tuesday, 22 September 2015 - 16:10 CET.
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