I’m currently developing an android (and probably iOS in the future) application for my company.
I was wondering what is the most unique data identifier to authenticate the users. A data that cannot be repeated through users.
Email? That user can log in with another phone using the email and password
Phone number? Could be the most unique one but it would required to verify the phone and I will have to setup a SMS validation service like WhatsApp
IMEI? It pretty much validates the unique phone but it can be spoofed or replaced. Although I don’t know if the application required permissions for this.
EDIT: Maybe a mix of all this methods?
My main goal is to save this data as a database and make it the primary key of it and with this know exactly who’s the user that it’s really using the company web services.
I hope you guys can help me.