Related: North Korea has a secret diplomacy network which transmits messages from Pyongyang to North Korea embassies worldwide. Radio hobbyists have successfull

Related: North Korea has a secret diplomacy network which transmits messages from Pyongyang to North Korea embassies worldwide. Radio hobbyists have successfully reverse-engineered its modem and protocol. This is quite unusual, we don't know the internal workings of any similar systems used by other governments, so reading about the North Korean system can give us a idea about what a typical, sophisticated shortwave digital communication system used by a government might look like. Another fascinating fact is the system sometimes transmits cleartext messages! The system allows two types of messages to be sent. The first type is fully encrypted normal messages, but one can also send "chat" messages, which allows the operators of two systems to communicate about their working schedule, system maintenance, etc, and they are unencrypted plaintext, which revealed a lot of about the internal of this system. Opsec failure? They should really just use a hardcoded symmetric key for this purpose... Network Structure: * The North Korean diplomatic shortwave network follows a forwarding tree structure, as they limit contacts between their stations to hops of usually no more than 5000 kilometers. Pyongyang sits at the root at the tree structure, as ultimate origin or recipient of all messages between it and embassies. Messages from Pyongyang are transmitted and relayed by North Korean embassies across the world, hop by hop along each branch of the distribution tree, until they are received by their final recipients. Messages from embassies are relayed and forwarded back to Pyongyang in the reverse way. http://priyom.org/diplomatic-stations/north-korea/network http://priyom.org/diplomatic-stations/north-korea/network Protocol: * North Korean diplomatic communications utilize a proprietary ARQ modem of unknown name, unofficially known as DPRK-ARQ. The modem is based on BFSK bursts transmitted in lower sideband mode. There are two possible waveforms: 600Bd/600Hz as the default, and 1200Bd/600Hz as an option. A complete protocol analysis is given by: http://priyom.org/diplomatic-stations/north-korea/dprk-arq-protocol http://priyom.org/diplomatic-stations/north-korea/dprk-arq-p... Message Format: http://priyom.org/diplomatic-stations/north-korea/message-format http://priyom.org/diplomatic-stations/north-korea/message-fo...