RedPhone is a free and open source application for Android devices, created by Whisper Systems, that lets you make encrypted voice calls from your device to other RedPhone users. Calls with RedPhone are only possible when device is connected to the Internet.
The ability to encrypt voice calls to other RedPhone users.
The ability to send encrypted voice calls over the Internet (instead of relying on your mobile provider).
Privacy from your mobile provider with regard to whom you calling as well as what you are saying.
Step 1: On your Android device, download and install the app from the Google Play store by tapping 
.
Figure 1: RedPhone on the Google Play Store
Step 2:. Before the installation process begins, you will be prompted to review the access that the application will have on your phone. Review this carefully. Once your are happy with the permissions that will be granted, press 
and the installation will complete. If you do not agree with the permissions that will be granted, press the back button and the installation will be cancelled.
Figure 2: Permissions required
Step 3. Tap Open to run the app for the first time.
Step 1: Begin the registration process by choosing the country your SIM card was purchased and entering your phone number and press 
Step 2: Verify that the number you entered is correct and press 
, otherwise press 
and correct your phone number.
Figure 3 & 4: Registration screen and confirming number
Step 3: RedPhone will proceed with the registration. During this process you will receive one SMS to complete registration.
Note: If for some reason you do not receive the SMS you will be given the option to receive an automated phone call where you will hear a 6-digit code, this code once entered will complete the registration.
Figure 5: Registration completing
After RedPhone has been registered you will be brought to the main screen, this shows you all the RedPhone users in your contact list on your phone.
Figure 6: RedPhone contact list
To make an encrypted call with RedPhone
Step 1: Open the RedPhone app.
Step 2: From the main screen, tap on the contact you wish to call.
Step 3: RedPhone will start ringing the contact.
Step 4: Once the call is answered by your contact, RedPhone will display two orange words in the middle of your screen. To ensure the call is secure not being intercepted, it is important that you verify that you both have the same set of words displayed on your phones, by reading them out at the beginning of the call.
Figure 7 & 8: RedPhone calling and call answered
Receiving a call with RedPhone is similar to receiving a regular phone call on your Phone.
Step 1: When a RedPhone call comes in it will display a screen with the message REDPHONE CALL in the centre of the screen.
Step 2: Swipe 
right to answer or left to reject the call.
Step 3: When you answer the call, RedPhone will display two orange words in the middle of your screen (*See Fig. 8). To ensure the call is secure not being intercepted, it is important that you verify that you both have the same set of words displayed on your phones, by reading them out at the beginning of the call.
Figure 9: Receiving an encrypted call with RedPhone
From the main screen of RedPhone you will have 4 tabs along with your contacts list.
Option 1: 
will display your contacts who use RedPhone.
Option 2: 
will display your call history. 
indicates you made a call to a contact. 
indicates a call received from a contact. 
indicates a missed call from a contact.
Option 3: 
will display your frequently called contacts.
Option 4: 
will give you a phone dialler so that you may diall RedPhone users who are not in your addressbook. Note: This dialler will not allow you to call Non-RedPhone contacts. If you try, RedPhone will give you the option to send a RedPhone download link to your contact.
Figure 10: Send a download link to a contact
Option 5: If you call a RedPhone user from your regular phone dialler, you will be asked if you would like to make a secure call. Tap Yes,Secure to upgrade to an encrypted call or tap No to make a normal unencrypted call.
Figure 11: Upgrade to a secure call
