The app has no ads, does not track users' data, and does not store any metadata such as timestamps, internet addresses or group names so it can't give them up if asked. It is considered one of the most secure systems in the world. A company called Whisper Systems created two encrypted apps, RedPhone for voice calls and TextSecure for texting.

With news this week of the messaging app being used to discuss war plans, we get you up to speed on what Signal should be used for—and what it shouldn’t.

The app can also be set to delete older messages after a period of time. Who uses Signal? Signal is used by government officials, but it is not meant to be used to discuss classif