Interesting proprietary adaptive HF modem spotted on 6670.0 KHz/USB. The modem uses a set of modified waveforms from 188-110A and STANAG-4539 and switches from 300bps (MS-110A) up to M4800 modes (S-4539) with constant modulation rate of 2400 symbols/sec. Note the presence of the four initial tones in each transmission which are non provided in the mentioned standards.
The link between the caller/called nodes "CAMP" and "OUTPOST" is established and terminated using 2G-ALE MS-141A. Both these callsigns are unknown to me, since their literal meaning they could probably belong to a military-like organized staff, probably Swiss Army or Swiss Emergency, but so far there is no confirmation about.
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| Fig. 1 - a MS-110A transmission |
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| Fig. 2 - a S-4539 (MS-110B) transmission |
Me and KarapuZ investigated the bitstream after the removal of the overheads due to the bearer HF waveforms and found a 128-bit period protocol which exhibits the constant 40-bit sequence
1111111110111111111111101111011111110110
in the preamble of each transmission (no matter if MS110-A or S-4539).
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| Fig. 3 |
After synched the stream on that (supposed) sync sequence, we found four times repeated 88-bit structures that look like a 88-bit key encoder: probably the (4-times repeated) 80-bit sequences act in the same way of the initialization vectors in KG-84 encrypted data blocks.
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| Fig. 4 |
