The Secure Sockets Layer (SSL) protocol allows applications to transmit sensitive data securely and to the appropriate person, by offering certificate-based authentication of clients and servers. It's both an encryption protocol (method of scrambling data so that it cannot be intercepted and understood without the key), and an authentication protocol (method of determining that you are who you say you are).

Released in March of 1996, SSL 3.0 is the standard way of securing electronic transmissions across the Internet, due to its open and non-proprietary nature. All the major Web server vendors support SSL, including Netscape, Microsoft and Apache.

SSL uses both public and secret key cryptography. Public key cryptography uses a pair of keys, one private and one public, while secret key cryptography uses only one key for encryption. The dual key technique is advantageous because it allows you to give your public key to senders. The sender can encrypt the message with your public key and send it to you; you can then use your private (not publicly known) key to decrypt the message.

SSL encryption is useful to secure electronic data when you must send sensitive data over the Internet or any other open network. In a small business environment, it's usually used to secure part of an e-commerce capable web site, and thus allow secure credit card transactions.