http://isdb4l77sjqoy2qq7ipum6x3at6hyn3jmxfx4zdhc72ufbmuq4ilwkqd.onion/blog/20240604-simplex-chat-v5.8-private-message-routing-chat-themes.html
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.