Does it really? Source?
Discussion
Signal servers know all message metadata (timestamp, hash of participants ID, message size), the only thing they don't know is message content. If that model is ported to nostr, relays would know all metadata and if they don't restrict who can query it, any user can know all metadata.
You can't directly port it, but does it make sense to come up with a totally new protocol, instead of extending signal to these capabilities?
It already exists and it's already working, it's not a science experiment.
Signal is extended to nostr?
I meant that a new more private working protocol exists (simpleX), not that it was ported to nostr.
Do you have a link to the protocol description?
It's built into the protocol, and frankly, a somewhat inherit part of how most social networks work. You have to know an address for the sender for it to get there, if that is encrypted, than no one will know where their message is (unless every client is attempting to decrypt metadata for *every* message ever sent).
However, Signal has taken some exotic steps to reduce their ability to see those messages, namely leveraging enclave tech like SGX: https://signal.org/blog/building-faster-oram/
There are ways to obfuscate the identity of the sender/receiver, but that metadata still must be present unencrypted to allows messaging protocols to work. Maybe there's some crazy way to do it with quantum tech, but we're still a ways from that :D