The second link leads to http://priyom.org/military-stations/russia/message-format http://priyom.org/military-stations/russia/message-format, which reveals a fa

The second link leads to http://priyom.org/military-stations/russia/message-format http://priyom.org/military-stations/russia/message-format, which reveals a fairly simple format that relies on one-time pads. Each military unit has envelopes with unique word grids, e.g. https://i.imgur.com/ItpKnNy.png https://i.imgur.com/ItpKnNy.png The radio station transmits messages as envelope identifiers and line/column numbers of those grids, and recipients piece them together. Simple and impossible to break unless envelope contents leak. Given how rarely the system is used, it probably serves as a low-tech backup for high-tech radio systems.