@sun Basically you hand Signal a message without any authentication and they deliver it. The recipient decrypts it and can tell from the signature inside it was from you.

Anyone intercepting the traffic can't tell if two messages were from the same sender just by looking at any cryptographic signatures / key IDs that are exposed (it's a second monumental task to figure out who the signatures really belong to, unless you've really targeted your traffic interception to be close to the suspect you're surveilling)

https://signal.org/blog/sealed-sender/