18 November 2014

CIS FSK 200/1000


FSK 200/1000 is a technical name for a digital mode used by Russian Intelligence and possibly also Diplomatic stations. The name stands for its baud rate and shift - 200 bd speed, 1000 Hz shift between tones.

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The messages are encrypted bitstreams, sent in 288-bit blocks. Each block begins with control bytes 0x7D 0x12 0xB0 0xE6. The first two blocks of each message are significant, containing information on the amount of blocks, communication link ID, day of the month, serial number, message type, possibly the amount of encoded groups, and encoded decryption information.
A short recording may be heard  here

Below is an example of a FSK 200/1000 decoded transmission: you can see the mentioned keys (link ID, day of the month,...): reception was made on 17 November at 2020z, on 8123.0 KHz/USB:

----------------------------------------------------------
Block No 0 : Total Message Size 4 blocks : This transmission contains one message.
7d,12,b0,e6,00,00,00,00,00,00,60,00,10,00,00,00,00,08,20,04,00,04,00,08,40,0b,40,06,70,03,70,0e,20,0f,90,08
Block No 1  : Link ID 28680  : 17th of month  : Msg Number 002 : Msg Type 07145 : Group Count (?) 4
22796 00000 00000 00606 56197 35395 00893 60555
7d,12,b0,e6,00,33,15,00,b9,40,e0,e0,9c,10,7a,00,0a,02,00,05,82,0e,d8,0e,ba,3c,84,78,53,db,06,12,25,10,89,03
Block No 2
7d,12,b0,e6,00,55,00,00,00,00,00,00,00,00,00,00,00,0a,00,0f,00,0a,00,09,00,01,00,00,00,03,00,04,00,05,00,04
----------------------------------------------------------
Block No 0 : Total Message Size 4 blocks : This transmission contains one message.
7d,12,b0,e6,00,00,00,00,00,00,60,00,10,00,00,00,00,08,20,04,00,04,00,08,40,0b,40,06,70,03,70,0e,20,0f,90,08
Block No 1  : Link ID 28680  : 17th of month  : Msg Number 002 : Msg Type 07145 : Group Count (?) 4
22796 00000 00000 00606 56197 35395 00893 60555
7d,12,b0,e6,00,33,15,00,b9,40,e0,e0,9c,10,7a,00,0a,02,00,05,82,0e,d8,0e,ba,3c,84,78,53,db,06,12,25,10,89,03
Block No 2
7d,12,b0,e6,00,55,00,00,00,00,00,00,00,00,00,00,00,0a,00,0f,00,0a,00,09,00,01,00,00,00,03,00,04,00,05,00,04
----------------------------------------------------------
Block No 0 : Total Message Size 2 blocks : This transmission contains 0 messages.
7d,12,b0,e6,00,00,00,00,00,00,30,00,08,00,00,00,00,04,10,02,00,02,00,04,20,05,a0,03,38,01,b8,07,10,07,c8,04
Block No 1  : Link ID 28680  : 17th of month  : Msg Number 002 : Msg Type 07145 : Group Count (?) 4
22796 00000 00000 00606 56197 35395 00893 60555
7d,12,b0,e6,00,33,15,00,b9,40,e0,e0,9c,10,7a,00,0a,02,00,05,82,0e,d8,0e,ba,3c,84,78,53,db,06,12,25,10,89,03
Block No 2
7d,12,b0,e6,00,55,00,00,00,00,00,00,00,00,00,00,00,0a,00,0f,00,0a,00,09,00,01,00,00,00,03,00,04,00,05,00,04
----------------------------------------------------------

FSK 200/1000 also has a concept of empty messages. These are always 4 blocks long, and include "00000" groups.
FSK 200/1000 operates in schedules of three transmissions, spaced 10 minutes apart.
The further transmissions are transmitted on lower frequencies. The frequency usage indicates worldwide operation. There also are unscheduled transmissions, using the communication link ID "00000", which may not repeat in regular manner.

FSK 200/1000 contents can be decoded using the free program Rivet, as in the following screenshot: