The Signal Protocol (formerly known as the TextSecure Protocol) is a non-federated cryptographic protocol that can be used to provide end-to-end encryption for voice calls, video calls,[3] and instant messaging conversations.[2] The protocol was developed by Open Whisper Systems in 2013[2] and was first introduced in the open source TextSecure app, which later became Signal. It has since been implemented into closed source applications, such as WhatsApp, which is said to encrypt the conversations of “more t
Source: Signal Protocol – Wikipedia