SSL (and its follow-on Internet standard TLS) is one of the most used security services. Most browsers and web servers implement the protocol. It is a transparent protocol that relies on TCP. An SSL session always begins with an exchange of messages called the SSL handshake. The handshake allows the server to authenticate itself to the client by using public-key techniques, and then allows the client and the server to cooperate in the creation of symmetric keys used for rapid encryption, decryption, and tamper detection. Optionally, the handshake also allows the client to authenticate itself to the server. The following figure describes the SSL/TLS handshake.