21 January 2016

Turkish Mil, FSK 600Bd/400Hz KG-84C

Although the signal is weak, you could easily find its basic parameters as in pictures 1 and 2. The signal has been heard on 07932.5 KHz (cf) around 0744z and also analyzed here by radioscanner.ru friends.
pic. 2
This signal use cipher NATO KG-84, it can be identified by the 64-bit sequence in each session (the KG-84 frame sync)
highlighted in pic. 3

The KG-84A and KG-84C are encryption devices developed by the U.S. National Security Agency (NSA) to ensure secure transmission of digital data. The KG-84C is a Dedicated Loop Encryption Device (DLED), and both devices are General-Purpose Telegraph Encryption Equipment (GPTEE). The KG-84A is primarily used for point-to-point encrypted communications via landline, microwave, and satellite systems. The KG-84C is an outgrowth of the U.S. Navy high frequency (HF) communications program and supports these needs. The KG-84A and KG-84C are devices that operate in simplex, half-duplex, or full-duplex modes. The KG-84C contains all of the KG-84 and KG-84A modes, plus a variable update counter, improved HF performance, synchronous out-of-sync detection, asynchronous cipher text, plain text, bypass, and European TELEX protocol. 
Compared to the KG-84A, the KG-84C had some interesting extras. It has a variable update counter,
improved HF performance, out-of-sync detection (when in synchronous mode), asynchronous ciphertext, plaintext bypass, and the European Telex protocol. When used with a suitable digital telephone unit, the KG-84 could also be used for secure voice transmissions. Data could be handled by the KG-84 in asynchronous mode at rates between 50 and 9600 baud. In synchronous mode, it could even go up to 32,000 baud (or even 64,000 baud when used in combination with an external clock). 

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