To deliver mesages, instead of user IDs used by all other platforms, SimpleX uses temporary anonymous pairwise identifiers of message queues, separate for each of your connections — there are no long term identifiers.
You define which server(s) to use to receive the messages, your contacts — the servers you use to send the messages to them. Every conversation is likely to use two different servers.
This design prevents leaking any users' metadata on the application level. To further improve privacy and protect your IP address you can connect to messaging servers via Tor.
Only client devices store user profiles, contacts and groups; the messages are sent with 2-layer end-to-end encryption.
