The future of Phone Number Authentication Webinar SMS one-time passcodes have become the default way to prove control of a mobile number, but they were not built for today’s threat landscape or customer expectations. Number Verify 2, part of the GSMA Open Gateway initiative, offers a different model: Network-based authentication that confirms the relationship between number, SIM, device and user without ever exposing a human-readable code that can be intercepted or phished.