Transport Layer Security (TLS) , formerly known as Secure Sockets Layer (SSL) , is a protocol used by applications to communicate securely across a network, preventing tampering with and eavesdropping on email, web browsing, messaging, and other protocols. Both TLS and SSL are client / server protocols that ensure communication privacy by using cryptographic protocols to provide security over a network. When a server and client communicate using TLS, it ensures that no third party can eavesdrop or tamper with any message.