Signal
Signal is a free, open-source, end-to-end encrypted messaging application for secure communication across mobile and desktop platforms. It uses the Signal Protocol to provide strong privacy features such as message encryption, disappearing messages, and screen security. The app is developed by the non-profit Signal Foundation and focuses on user privacy by minimizing data collection.
Developers should learn and use Signal when building or evaluating secure communication systems, as it sets a high standard for privacy and encryption in messaging apps. It is particularly useful for applications requiring confidential data exchange, such as in healthcare, finance, or activist contexts, where protecting user data from interception is critical. Understanding Signal's protocols can also aid in implementing similar security features in custom projects.