What is Data Encryption? - the process of encoding information in such a way that only the person (or computer) with the key can decode it

The simplest form of encryption is a table lookup.

Most computer encryption systems belong in one of two categories: Symmetric-key encryption and Public-key encryption.

Symmetric-key encryption

- Each computer has a secret key (code) that it can use to encrypt a packet of information before it is sent over the network to another computer.

- Each computer must be installed with the key.

- Each computer must know the key in order to decode the information.

Public-key encryption

- Uses a combination of a private key and a public key.

- Only the main computer knows the private key.

- The public key is given to any other computer by the main computer to communicate securely with it.

- The public key and the computers own private key is needed to decode an encrypted message.

Most computers use a combination of public-key encryption and symmetric-key encryption. This is because public key encryption on it's own takes up a lot of processing power. When two computers want to initiate a secure session, one computer sends a symmetric-key to the other which is encrypted with a public key. This then allows both computers to communicate using symmetric-key encryption. Once the session is over the symmetric-key is no longer needed and is discarded, however a new symmetric-key must be created next time the computers initiate a session with one another.

Algorithms

There are two groups of encryption algorithm that are important to the computer and telecommunications fraternities: secret-key cryptography (SKC) and public-key cryptography (PKC).

SKC is the traditional method of encrypting data and uses a single secret key known only to the sender and receiver of data. The standard in this area is known as Digital Encryption Standard (DES). PKC is more concerned with signature verification, which is a procedure that can verify the source of data, and also that the data has not been tampered with in transit. The two standards here are RSA and DSS. Let's look at secret key cryptography first.

Certificates

Certificates are digitally signed statements, which attest to the identity of a key holder. A certificate is used to identify who a person is at a public computer. It is possible for someone to create a public key and make up a name using common software.

Digital Certificates are needed when public-key encryption is used on a large scale. An example of this could be a large web server. A digital certificate is 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 confirms that the computers are who they say to be and then passes on the public keys from each computer.

Hardware