Thank you for your prompt feedback, I want to do something similar to Whatsapp, authenticate users…
Dennis Cheruiyot Koech

Yeah you are right. Finding contacts who are also using the app is basically intersection of two sets — your user base and the user’s contact list. Your backend has the user base. So you have to read the user’s contact list. For security reasons you may hash the contact numbers before sending to your backend. You can use digit’s Find Friends feature

I think digits now displays the App name in the SMS. Also you can customize the login UI. check this thread

Check digits documenation for more info