A lot of smart people said something that was eventually done with software was "physically" impossible? Who were these smart people exactly? I'm curious about

A lot of smart people said something that was eventually done with software was "physically" impossible? Who were these smart people exactly? I'm curious about the security layer. It sounds like a one-time pad kind of setup. If true, does that mean the devices involved have to be synched up in a different secured environment to share the encryption codes and the protocols on how they should be used? Eventually it will offer phone calls and text messaging? So you can call people in the immediate vicinity?