Secure Sockets Layer (SSL) and its successor, Transport Layer Security (TLS), are cryptographic protocols which provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers. There are slight differences between SSL 3.0 and TLS 1.0, but the protocol remains substantially the same. The term "SSL" as used here applies to both protocols unless clarified by context.SSL provides endpoint authentication and communications privacy over the Internet using cryptography. Typically, only the server is authenticated while the client remains unauthenticated; this means that the end user can be sure with whom they are communicating. The next level of security—in which both ends of the "conversation" are sure with whom they are communicating—is known as mutual authentication. Mutual authentication requires public key infrastructure (PKI) deployment to clients. SSL is used by numerous e-commerce web sites to secure payments over the Internet. This application also requires to obtain a certificat issued by a certificate authority.