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Encryption

One method of protecting data that is communicated in a network, especially a WAN, is the use of encryption. Encryption is a means of encoding the communicated data so that only the intended recipient with a key can decode the data so that it makes sense.

Computers encrypt data by applying an algorithm to a block of data. An algorithm is a set of procedures or instructions for performing a specified task. The strongest and most widely used form of encryption is known as public key or RSA encryption. A famous implementation of it is 'PGP' (Pretty Good Privacy). A private encryption key, or name, known only to the sender of the message and its intended receiver, is used to control the algorithm's encryption of the data, thus yielding a unique cipher text that can be decrypted only by using the key. Apart from its near perfect security, a side benefit of public key encryption is that data cannot be 'forged' and sent under an assumed identity: the key used to encrypt the data is as identifiable as a fingerprint and cannot be used to deceive recipients. It is also impossible to tamper with encrypted data: any changes to the data after it is encrypted are immediately obvious to the recipient.

To implement public key encryption on a large-scale, such as a secure Web server might need, requires a different approach. Digital Certificates are basically a bit of information that says that the Web server is trusted by an independent source known as a Certificate Authority. The Certificate Authority acts as a middleman that both computers trust.