I highly doubt that signal does anything to help with mass surveillance. Signal started keeping people's name, photo, phone number, and contacts in the cloud protected by a "secure" enclave the NSA almost certainly has access to and hackers already got into (https://community.signalusers.org/t/sgx-cacheout-sgaxe-attac...) and even leaving all that aside, all anyone needs is a PIN that can be trivially brute forced. (https://www.vice.com/en/article/signal-new-pin-feature-worri...)