Encryption

One of the most common methods for ensuring that data is not viewed by prying eyes and has no value to thieves is encryption.

Encryption is the encoding of data so that the plain text is transformed into something unintelligible, called cipher text. Because cipher text is unintelligible, the data is rendered useless to an intruder. This transformation comes about by combining the data with a key that is known only to the sending and receiving parties. The key acts as a code book that, along with the original data, is input into a series of algorithms that produces the cipher text. When the data is received by an authorized party, it is decoded into its original and more useful form through a reverse of the original process.

Two principal methods of encryption are used today. The first is private key encryption, also called symmetrical encryption. With this method, both parties have the same key and use it to encode and decode data. The advantage of this method is speed, but there are challenges in ensuring that the keys are distributed safely.

The second method is often called asymmetrical encryption. This method uses a publicly known key. The receiver then decodes the cipher text, using a key that is known only to the receiver but that matches the public key. In this way, anyone can send encoded text to the receiver, but only the receiver can decrypt it. Although often slower than private-key encryption, this method solves the problem of key distribution. No one can decode the text except the intended receiver.

Encryption is used to protect data on hard drives, as well as on tapes, and is the basis for most secure data and voice communications. In practice, asymmetrical-key encryption is used for quick transfers of information, especially the exchange of private keys, and to encode e-mails. Private-key encryption is used for secure communications channels.