The easy and convenient way of shopping from the Internet attracts customers from all over the world to shop on-line. Anyone can browse the millions of websites, like Amazon.com and Ebay.com, that sell a variety of items or hold on-line auctions, as long as they have Internet access. Most big chain stores in the United States have on-line stores that sell the items they have in the stores for the convenience of lazy shoppers. However, there are risks that shopper should consider before they decide to buy from a site. Aside from the quality of the item, they have to worry about the safety of the money transition on the web. Most sites accept credit cards as a method of payment. However, how can we be sure that giving out our credit card numbers over the Internet is safe? What if someone intercepts the transaction and steals our numbers? Can we trust the Internet?
People have been working with coding words and numbers to send secret messages or to keep information private for a very long time. For example, about two thousand years ago...