@avelino interesting idea. I'm hypocritical here since I actually do no protection of my phone number, but the phone number itself is the weakpoint, right? I respect several commenters who hate to regard phone numbers as personal identifiers, and somehow dwell in burner phones etc.
Related to this topic might be #DeltaChat @delta , which has all the decentralized characteristics of email itself. The concept is beautiful, although I couldn't make the leap a year or two ago when I tried it.