The Secret Behind Encryption

As machines in stores swipe our credit card details, or when we submit personal information online, we are promised that encryption and authentication codes will keep it all safe. But ever so often, computer hackers manage to crack into supposedly secure systems. This week for instance, the biggest credit card heist ever was reported in the news. Forty-five million credit and debit card details stored by the international fashion retailer TK Maxx were accessed by hackers, and it is thought that their intrusions date back to 2003. So how does encryption actually work? Are scientists working on more sophisticated systems that will be more trustworthy?

Credit: Tomasz Sienicki

The principle behind encryption is similar to using an old-fashioned padlock and key.

Using codes to protect information dates back to Roman times. Julius Caesar came up with a simple cipher to secretly communicate with his generals. His method involved substituting each letter in a word with another letter a fixed number of letters away in the alphabet. For example, if he chose to transpose each letter by five, B would become G, H would become M and so on. His generals would need to know the key, in this case a transposition of 5, to crack the message.

Of course, this is a very simple code and could be easily cracked by a person, not to mention a computer. But the principle behind encryption methods used today is still the same: computers rely on keys to secretly transmit information.

You may be familiar with Secure Socket Layer (SSL), a protocol used by Internet Explorer and many other web sites to transmit data. When you are about to enter private information, a padlock appears at the bottom of your browser and the 'http' in the web address is replaced by the more secure 'https'. To ensure that information is protected, a combination of two common encryption methods, symmetry and public key, are used.