examples of 2G-ALE followed by forward of data

MS188-141A + MS188-110A serial

MS188-141A + MS188-110A App.B

CODAN

MS188-141A + R&S GM2100

MS188-141A + voice comm

R&S ALIS + R&S GM2100

THALES Skymaster ALE + THALES TRC 177x serial modem

MS188-141A + STANAG-4285

KG-84 evidences

I tried out to look at some signals that use KG-84 encryption (based on Saville algorithm) in order to identify its footprint inside them and differences (if any), specifically: the two NATO widely used waveforms STANAG-4285 and STANAG-4481-FSK, one of the STANAG-4285 variants (this one possibly a Croatian version) and the FSK 600Bd/400Hz by Turkish Military. Since only four waveforms, this does not claim to be a complete view, rather it will be updated as soon as I'll get other such encrypted signals.

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Given a signal, as previously seen, the existence of  KG-84 encryption can be detected by its well-known 64-bit sync pattern that is inserted at the beginning of each session/message and followed by the encryption initialization:

 1111101111001110101100001011100011011010010001001100101010000001

In order to highlight the sync pattern we need to work with bitstream files, also known as ASCII-bits file, containing only the binary symbols 0 and 1 and provided by decoders such as k500 or Sorcerer (in the picture belows). This because - for example - the PSK-8 demodulated output from signals analyzers such SA, provide on-the-air symbols that still contains extra-symbols due to FEC and they should de-scrambled, de-interleaved and converted from HEX values to binary. 
The bitstream analysis is performed using a bit flow processor and editor.

STANAG-4481P (STANAG-4285 300bps/L)
 

pic. 1 - NATO STANAG-4481P

in this case the sync is followed by a 512 bits group consisting of two 64 bits sequences repeated 4 times: the two 64 bits sequences form the 128 bits key, k500 call them as "inizialization vectors" and are clearly indicated in its output as two strings each of 32 HEX characters. As far as I can see, both the sync and the key are inserted at the beginning of the session and are not re-inserted or repeated so that the message can not be deciphered in case of late entry.

STANAG-4481F (FSK 75Bd/850)

pic. 2 - NATO STANAG-4481-FSK

since the same operating environment (NATO), STANAG-4481-FSK adopts the same structure as in 4285. It is worth noting in pic. 3 that the 64-bit sync patterns produce ~850ms ACF spikes visible in the initial part of the signal.

pic. 3 - 850ms ACF spikes due to key insertion

STANAG-4285 variant

pic. 4 a STANAG-4285 variant

although it's compatible with NATO S-4285, this waveform (the user is suggested to be Croatian) does not provide KG-84 encryption (coud not find the sync pattersn) but rather a sort of linear encryption taht is not detected by the standard S-4285 decoders such as k500 and Sorcerer.

Turkish FSK 600Bd/400Hz

pic. 5 - the Turkish FSK/600/400

for what concerns KG-84 encryption, this waveform exhibits an interesting peculiarity: the sync pattern is not followed by the 512-bits key block as seen in NATO 4285 and 4481 implementations. I do not know if the  128 bits immediately following the syncr are indeed the key or else the key is obscured to standard decoders. 

As expected, since this trasmission consists of 7 blocks, the sync is repeated  7 times each 3954 bits exactly: since the apparently lack of the key I don't know if the transmission carries seven distinct messages or if the repetion is an help in case of late entry (so the messages are the same?).

pic. 6 - the seven resolvers

It's quite useless and waste of space and bandwidth to list here concepts and images that are easily found on the web about KG-84, below just few links:

https://en.wikipedia.org/wiki/KG-84 

https://www.ia.nato.int/niapc/Product/Elcrodat-4-2_124

http://www.jproc.ca/crypto/kg84.html

http://www.cryptomuseum.com/crypto/usa/kyk13/index.htm

Thanks to my friend KarapuZ for pointing me this argument and his stimolous to deepen.

BELL 103 compatible FSK modem 300Bd/200 (Algerian AF)

heard on 11446.2 KHz (cf) at 0756 UTC. FSK bursts preceeded by three unmodulated tones 150 Hz spaced, manipulation speed is 300 symbols/s and shift is 200 Hz. A short 250ms preamble is embedded in the 3 pre-tones (pic.3) , data are encrypted. Since the baudrate (300Bd) is higher than the shift (200Hz), modulation could be a so-called semi-mode such as MSK or GMSK.

The waveform is compatible with AT&T Bell 103 modem and suggested to be used by Algerian Air Force. A short recording is available here

 

pic. 1 baudrate 300Bd

pic. 2 shift 200 Hz

pic. 3 FSK preamble

Iranian-QPSK 468.75, 937.5 Baud

Heard on 10724.0 KHz and 17382.2 (cF) on USB at 2120z, this signal is known as "Iranian-QPSK" since its QPSK modulation QPSK. For what is known, the Iranian-QPSK occurs in some variants that differ in speed such as: 1875, 937.5, 468.75 and 207 Baud. It seems that there is also a variant with a speed of 234 baud. The 207 Baud waveform is reported in radioscanner.ru while qrg.globaltuners.com   identifies the signal as belonging to the Iranian Navy: I did not find such match looking at UDXF logs.

 

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.1

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)

1111101111001110101100001011100011011010010001001100101010000001

highlighted in pic. 3

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). 

https://en.wikipedia.org/wiki/KG-84

https://www.ia.nato.int/niapc/Product/Elcrodat-4-2_124