While cryptography is the science of securing data, cryptanalysis is the science of analyzing and breaking secure communication. Classical cryptanalysis involves an interesting combination of analytical reasoning, application of mathematical tools and pattern finding. New cryptographic algorithms need to be designed considering the probable future developments while working on their designs, as continuous improvements in computer processing power have increased the scope of brute-force attacks. Thus we may have to think about increasing the key lengths and block lengths. There are mainly two types of crypto-systems, namely, symmetric crypto-systems and public crypto-systems.