TLS – Transport Layer Security
(TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols designed to provide communication security over the Internet. In the Internet Protocol Suite, TLS and SSL encrypt the data of network connections in the application layer. Since protocols can operate either with or without TLS (or SSL), it is necessary for the client to indicate to the server the setup of a TLS (or SSL) connection. Then the client and the server use the session keys to encrypt and decrypt the data they send to each
other and to validate its integrity.
The SSL protocol was originally developed by Netscape. Version 1.0 was never publicly released; version 2.0 was released in February 1995 but contained a number of security flaws which ultimately led to the design of SSL version 3.0. Newer versions of SSL/TLS are based on SSL 3.0. TLS is a standard protocol.