If you have ever shopped online, chances are you had to enter your credit card information to pay for the items you purchased. Sending a credit card number over the Internet can be risky business, because anyone could intercept that transmission. To prevent that, websites use a variety of security measures, most of which involve some form of cryptography. Most websites utilize SSL (Secure Sockets Layer), a public-key encryption system, to secure the connection between your web browser and their web server. Any information you send to the site, or that the site sends back to you, is encrypted while it is transferred from one to the other, protecting credit card information, passwords, personal data, or anything else you need to enter.