SimpleX does not, not even random numbers. This radically improves your privacy. When users have persistent identities, even if this is just a random number, like a Session ID, there is a risk that the provider or an attacker can observe how the users are connected and how many messages they send. They could then correlate this information with the existing public social networks, and determine some real identities.
Even with the most private apps that use Tor v3 services, if you talk to two different contacts via the same profile they can prove that they are connected to the same person. SimpleX protects against these attacks by not having any user IDs in its design. And, if you use Incognito mode, you will have a different display name for each contact, avoiding any shared data between them.
Many users asked: if SimpleX has no user identifiers, how can it know where to deliver messages? To deliver messages, instead of user IDs used by all other platforms, SimpleX uses temporary anonymous pairwise identifiers of message queues, separate for each of your connections โ there are no long term identifiers. You define which server s to use to receive the messages, your contacts โ 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. Read more in SimpleX whitepaper. Trail of Bits is a leading security and technology consultancy whose clients include big tech, governmental agencies and major Blockchain projects.
