Private message routing is a major milestone for SimpleX network evolution. It is a new message routing protocol that protects both users' IP addresses and transport sessions from the messaging relays chosen by their contacts. Private message routing is, effectively, a 2-hop onion routing protocol inspired by Tor design, but with one important difference - the first (forwarding) relay is always chosen by message sender and the second (destination) - by the message recipient. In this way, neither side of the conversation can observe IP address or transport session of another.