Cryptography is art of illusion within which the sender encodes the message employing a key and sends it over the line. The receiver on the opposite facet of the channel decodes the message back and victimization the key tries to get back the initial message. In case the key throughout the communication is same on each side then it's referred to as radial key cryptography and if is termed as uneven key cryptography. There have been completely different secret writing techniques used for the plain text called as block & stream cipher. The modes for encryption are ECB, CBC, OFB & CFB. In this paper we propose a symmetric key algorithm using CBC mode of encryption with high complexity
Key words: CBC, Symmetric Key, Bifid, Transposition.