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CK-42
COMSEC Controlled Item - wanted item

CK-42 was a small encryption device that was also used as a burst encoder, developed in the US in the late 1970s for use by the CIA in clandestine operations and espionage in 'hostile' countries. The device was often used in combination with spy radio sets like the CDS-501 and the RS-804.
 
The first publicly documented use of the CK-42 dates back to 1980, when the CIA reportedly smuggled the first CDS-501 radio set into Cuba for use by their agents in or near Havana [1].

The device measures only 100 x 68 x 18 mm and weights just 160 grams, extemely small for its age, making it very easy to hide the device. It has a memory capacity of 1579 characters that are encrypted with a 19-character key. All text is entered on the keyboard by means of a stylus. Including the message preamble, the longest message that can be sent is 1596 characters.
  
Artist impression of the CK-42. Copyright Crypto Museum 2015.

The device is connected to an external battery or a transmitter, via a connector at the top. Once a message is stored in the device's internal memory, and the device is connected to a transmitter, it can send the message as a high-speed data burst that takes 4 to 21 seconds, depending on the length of the message. The device was first used with the CDS-501 line-of-sight (LoS) transmitter and shortly afterwards also with the RS-804 satellite communicator. Although the CK-42 unit is labelled as COMSEC Controlled Item, many of them are known to have fallen into enemy hands.

The CK-42 was introduced around 1980, but it took several years before the radio sets that were supplied with it, were reliable enough for field use. The device is known to have been used in the Soviet Union (USSR), Cuba, Poland and East-Germany (DDR), right until the end of the Cold War.
 
Complete RS-804 set as photographed by the KGB [3]. Photograph kindly supplied by the Polish Institute of National Rememberance [4]. Complete RS-804 set as photographed by the KGB [3]. Photograph kindly supplied by Detlev Vreisleben [2]. Complete RS-804 set with antenna, as photographed by the KGB [3]. Photograph kindly supplied by Detlev Vreisleben [2].

 
Controls
The diagram below shows the control panel of the CK-42. The device connects to the transmitter via a wide connector at the top. Messages are entered via the 32-button keypad that should be operated with a sharp object like a stylus. There is no optical feedback of the entered data. For a full description of its operation, please refer to the desciption of the CDS-501 or RS-804 radios.


Before entering a message, a 19-character encryption should be entered. The keys were supplied on a separate sheet and a new key was used for each message. According to [1 p.29], the keys were supplied to Cuban agents printed on plastic tape. Each tape was suitable for 135 messages.
 
Captures
The CK-42 was compromised in several cases, along with the associated radio sets. There are documented cases of captures of this equipment in Cuba in 1983 and in Russia, also in 1983 [2]. Furthermore, it is suggested in [1] that the Cubans were able to capture quite a few of these devices. The same device were also captured by the Russians in Afghanistan at late as 1988.

 More information about the Cuban capture
 More information about the Russian capture
 
Help required
Although the CK-42 and the accompanying CDS-501 and RS-805 radio sets are mentioned and described in several publications [1][2][3], there is very little detailed information about these devices in the public domain. At present we have no better pictures than the ones shown above and the encryption algorithm is still unknown. As the devices are no longer in use and many of them have fallen into the hands of 'hostile' countries during the 1980s, there can be no good reasons to withhold such information. If you have any further information, please contact us.
 
References
  1. José Luis Morera et al., The CIA's War Against Cuba
    Havana, 1988. Published by the Cuban National Information Service
    in cooperation with the Ministry of the Interior of the Republic of Cuba.

  2. Jan Bury, Project Kalina: The Lotos Operation Conundrum
    Cryptologia 36:2, April 2012, pp. 119-128.

  3. Robert Wallace & H. Keith Melton, Spycraft: The secret story of the CIA's Spytechs...
    2008. ISBN 978-0593062043.

  4. Archives of the Polish Institute of National Remembrance (IPN)
    Information on the PHOBOS agent radio communications device from the First
    Secretary of the US Embassy in Moscow R. Osborne on 7 March 1983. Warsaw 1983. 1
    Available at the Archives of the Polish Insitute of National Remembrance. File # IPN BU 01304/953.

  1. Original text: Informacja dotyczaca agenturalnej aparatury lacznosci radiowej 'FOBOS' zatrzymanej u pierwszego sekretarza ambasady USA w Moskwie R. Osborne'a w dniu 07.03.1983 r. Warszawa 1983.

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