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HC-590
Computer encryptor · CRYPTOMATIC - this page is a stub

HC-590 was en encryption/decryption device for serial RS232 computer signals up to a speed of 1200 baud, developed in the early 1980s by Crypto AG (Hagelin) in Zug (Switzerland). The device is part of the CRYPTO­MATIC family (HC-500-series). It uses a cryptographic algorithm developed by the US National Security Agency (NSA), that contains an exploitable weakness (backdoor) [1].

The device is housed in a 3U 19" rackmount enclosure, and has a white front panel, with a physical KESO lock at either side. The leftmost lock is used for enabling the device and entering the Basic Key (BK), whilst the rightmost one is used for selecting the MODE of operation.

At the left, just above the lock, is a power LED indicator. At the right are four further indicator for plain text, encryption, decryption and error respectively. All connections are located at the rear. At present, no further information about the HC-590 is available.
  
Crypto AG (Hagelin) HC-590 computer encryptor. Image taken from company brochure.

Although it has not yet been confirmed, it is likely that this device was developed at Motorola in Phoenix (Arizona, US) and that it is based on the same basic design as the HC-570 and HC-550, featuring a Motorola 6800 microprocessor [2], in which the algorithm is implemented in software.

Compatible machines   Cryptomatic 500
Pocket version, resembling a calculator Briefcase version Desktop model, based on Siemens T-1000 Desktop model Desktop model, based on Siemens T-1000 Rackmount model for serial computer signals
HC-590
History
The machine was developed at a time when the company – Crypto AG – was jointly owned by the German Bundesnachrichtendienst (BND) and the American Central Intelligence Agency (CIA). The cryptologic — i.e. the part that contains the cryptographic algorithm — was developed by the US National Security Agency (NSA), and contains a exploitable weakness (backdoor) that could be used to the advantage of the NSA and the German ZfCh.

The cryptologic comes in two flavours: readable 1 and unreadable. Unreadable versions were secure and were available to all NATO countries, plus Switzerland and Sweden. Readable versions were sold to all other countries, with very few exceptions.

  1. In this context, readable means that the cryptographic algorithms could be broken by the NSA. Also known as friendly. In contrast: algorithms that are not breakable by NSA, are called unfriendly or unreadable.

References
  1. Crypto Museum, Operation RUBICON
    February 2020.

  2. Wikipedia, Motorola 6800
    Retrieved December 2019.
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Crypto Museum. Created: Sunday 05 January 2020. Last changed: Monday, 10 February 2020 - 15:06 CET.
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