Abstract: The present invention provides an encryption and decryption method and system to encipher and decipher binary data. The operation of the system is controlled by parameter values. The data to be encrypted is divided into blocks of tokens. Multiple copies of these blocks are created. In each token bits are moved into the lowest order bits according to a pattern. The highest order bits are replaced by pseudo-random bits. A series of modulo additions and rotations are performed and then a substitution operation and a transposition operation are performed producing the final cipher text. The decryption method is the reversal of the encryption method.