Smartphone apps to encrypt messaging and calls

One should also distinguish between secure messages that are archived for users to access later, as you usually expect with texts, and ephemeral messages specifically not stored in the cloud or on servers and that will disappear locally after a set amount of time. Some of these apps offer both, and some have settings to change how long messages last. Most apps specifically only allow you to message or call other users of the app, but even if an app allows you to message or call your whole contact list, the communication will not be secure end-to-end.

via Apps to easily encrypt your text messaging and mobile calls.