We want to let users register on our Mobile App with their Phone Number, then verify it using SMS without the need to enter a password -- may be like what WhatsApp is doing with their on-boarding process:
We want the registration scenario to be user-friendly & to help us giving a secure authentication later on, which is really hard without having a password, so user identity will be his number & his verified Mobile Device (& also we may consider the SIM ID for security purposes)
We tried to list the different combinations about how to be sure of user identity between these factors:
- Phone Number (old/new)
- Device Id (old/new)
- SIM Id (old/new)
and we were overwhelmed with the large number of scenarios that we should handle, like for example, if a registered user (old number) bought a new mobile (new Device Id) & wants to open our app there!
.. So, What is the best simple scenario for Mobile-App registrations using phone number?