Secure links between your computer and another computer over the Internet are based on a code system called public key encryption. When you form a secure connection over the Internet, you will usually be using a protocol called a Secure Sockets Layer (SSL), developed by Netscape, but used by both Netscape and Microsoft browsers.

When your computer makes a secure link with another computer through the Internet, each computer generates a set of codes to encrypt information. From these codes, each computer creates two "keys," one private and one public. Your computer keeps the private key secret, but sends out the public key to the other computer, which uses that key to encode subsequent messages so that only your computer can read them. The public key cannot, however, be used to decode the message; the decoding can only be done using the private key.

These keys allow you and the other computer to lock and unlock information so that only the holder of the private key can read messages encrypted by the public key. Since only you and the other computer have a copy of your respective private keys, there is no way for anybody else to intercept and decode your messages.

Still curious? Find out about how secure links work in more detail.