Abstract: “The concept of public key Cryptosystem evolved from an attempt to attack two of the most difficult problems associative with symmetric encryption. The initial problem is that of key distribution. As we have seen, key distribution under symmetric encryption requires either (1) that two communication already share a key, which somehow is distributed to them; or (2) the use of key distribution centre. Finally, there is a feeling that key distribution is trivial when using public key encryption, compared to the rather cumbersome handshaking involved with key distribution canters for symmetric encryption. This paper provides an overview of various public key algorithms and a comparison between them is made on the basis of Key size, security and Cost. First we discuss the RSA algorithm, Diffie Hellman Key Exchange Algorithm and EC Cryptography – (ECDH – Elliptic Curve Diffie Hellman) and a comparison between them is made on the basis of Key size, security and Cost.”

Keywords: YCbCr, HSI, Matlab