Symmetric and asymmetric encryption

Abstract

All cryptosystems currently in use are symmetric in the sense that they require the transmitter and receiver to share, in secret, either the same piece of information (key) or one of a pair of related keys easily computed from each other; the key is used in the encryption process to introduce uncertainty to an unauthorized receiver. Not only is an asymmetric encryption system one in which the transmitter and receiver keys are different, but in addition it is computationally infeas-ible to compute at least one from the other. Asymmetric systems make it possible to authenticate messages whose contents must be revealed to an opponent or allow a transmitter whose key has been compromised to communicate in privacy to a receiver whose key has been kept secret - neither of which is possible using a symmetric cryptosystem. This paper opens with a brief discussion of encryption principles and then proceeds to a comprehensive discussion of the asymmetric encryption/decryption channel and its application in secure communications.