I wonder if something like the strategy used for Certificate Transparency could work here? Take a legacy system, attach authentication on the side, propagate th

I wonder if something like the strategy used for Certificate Transparency could work here? Take a legacy system, attach authentication on the side, propagate that data in a manner that allows looking it up, use it as a strong signal for "this is actually authentic", and then slowly ratchet that up until people feel comfortable saying that calls without it can go straight to voicemail without ringing.