People use computers for an ever-increasing number of tasks. Just a few years ago, a PC was scarcely more than a fancy word processor. Over the years, we have started using it for filing taxes, online shopping, e-mail, listening to music, on-line banking, bill payment, and stock trading; the list keeps growing. As the list grows, so does the amount of private information we store in on our PCs. If you want your private information to remain private, you must take steps to keep it so. If you don’t, it is potentially available to anyone who can access your computer – children, friends, houseguests, neighbors freeloading on your insecure wireless network, and even hackers.
One solution to the problem is to restrict access to your computer – you can lock your computer in a room and wear the key around your neck. Anyone who wants to access information on your computer without your approval will have to wring your neck first, an act you will most likely resist. The problem, however, is that this solution not only restricts access to the information on the computer, it restricts access to the computer itself. No one but you can use it. Besides, it does not protect your information from folks who may be able to access it without unlocking the room, such as hackers.
A better solution would be to “lock” just the sensitive information. This would allow others to use the computer, but they won’t be able to access the locked information. There are various ways you can go about “locking” information. You could protect files containing sensitive information using Windows account level security, for example, but almost all account level security has a backdoor – anyone with an administrator’s rights to the computer has unrestricted access to the information on it. Or you could use the password feature provided by applications such as Microsoft Word and Microsoft Excel. But this scheme, too, has drawbacks. To begin with, every application you use must support password protection, which certainly is not the case. (Did you ever try protecting a notepad document?) Secondly, to avoid confusion, you will probably want to use the same password for all documents. This, as you may very well know, is wishful thinking because each application has different rules for how long the password can be and what characters it can contain. Lastly, if you ever want to change the password, you will have to open every protected document and change its password.
A more viable alternative would be to scramble the information in such a way that only you and people you authorize can unscramble it. Scrambling of information is called “encryption” and unscrambling of information is called “decryption”. If you encrypt information, you don’t have to worry about restricting access to it. You can leave it in plain sight for everyone to see or even copy. It will make sense only to those who can decrypt it; to others, it will look like a collection of meaningless letters and digits. The science of encryption and decryption is called “cryptography”, which literally means “hidden writing”. Cryptography is useful in protecting everything from military messages to the contents of your disk.
In daily life, people encrypt and decrypt information without a thought. Take me, for example. I am an immigrant; my children are American. When I want to say something to my wife that I don’t want my children to understand, I speak to her in my native tongue. In a sense, I encrypt the information. My wife can decrypt it but my children can’t, because my wife has the “key” to decrypt what I say – the language. (Incidentally, I also know of another family like mine, where the children get back at their parents by speaking among themselves in Spanish!)
Or take little children playing Spy Vs. Spy. They talk to each other in a code such as Pig Latin. They are encrypting information too. They know that to encrypt, they must remove the first letter of every word and place it at the end of the word. To decrypt, they must remove the last letter and place it at the beginning of the word. The key is to know this little secret.
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