Encryption: Key Systems

There are two main types of encryption system, Symmetric and Asymmetric.

Symmetric Key Cryptography
With this system the sender and receiver of a message use a single common key to encrypt and decrypt the message. The symmetric system is the simplest and fastest type of encryption, but the main drawback is that the two involved parties must somehow exchange the key in a secure manner. Symmetric key cryptography is sometimes known as Secret Key Cryptography. Probably the most popular symmetric key system at the time of writing is DES. A big advantage of Symmetric Key Encryption over Asymmetric Key Encryption is speed.
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Asymmetric Key Cryptography
With the asymmetric system two keys are used. A public key to encrypt messages and a private key to decrypt them. The advantage of public key encryption is that the public key can be made available easily to anybody (in fact it has to be for the system to work) and this avoids the problem that faces symmetric key encryption which involves the secure exchange of a single key. The private key is never transmitted.
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