The maker of Red Phone and Text Secure for Android has moved to iOS to offer encrypted calls.
Whisper Systems has developed “Signal” which allows a user to enter their phone number, put in the confirmation code and this will automatically import a contact list during the first use, so it’s just a question of how many of your friends are already on the app, according to The Verge.
The app connects with RedPhone users in your contact list will pop automatically into the app and it does not leave any metadata and all an observer would see is that you called Signal’s servers, and developers say the server doesn’t keep any logs that could be pulled after the fact.