  Cryptography is an art and science of secure communication. Here the sender
and receiver are guaranteed the security through encryption of their data, with
the help of a common key. Both the parties should agree on this key prior to
communication. The cryptographic systems which perform these tasks are designed
to keep the key secret while assuming that the algorithm used for encryption
and decryption is public. Thus key exchange is a very sensitive issue. In
modern cryptographic algorithms this security is based on the mathematical
complexity of the algorithm. But quantum computation is expected to
revolutionize computing paradigm in near future. This presents a challenge
amongst the researchers to develop new cryptographic techniques that can
survive the quantum computing era. This paper reviews the radical use of
quantum mechanics for cryptography.
