I have not looked into how it works, other then reading the blog post, but it seems like they are trying to figure out that part as well: https://signal.org/blo

I have not looked into how it works, other then reading the blog post, but it seems like they are trying to figure out that part as well: https://signal.org/blog/sealed-sender/ https://signal.org/blog/sealed-sender/ But yeah, as long as they own the servers I am sure they could puzzle it together if they wanted.