  Nowadays security in communication is increasingly important to the network
communication because many categories of data are required restriction on
authorization of access, modify, delete and insert. Quantum cryptography is one
of the solutions that use property of polarization to ensure that transmitted
data is not tampered. The research paper provides the mechanism that enhances
the data security in quantum cryptography during exchange of information. In
first phase detailed explanation of Quantum key distribution's BB84 protocol is
given. BB84 protocol is used as the basis for the mechanism. In next phase the
proposed mechanism is explained. The proposed mechanism combines BB84 protocol
at two levels, from sender to receiver and then from receiver to sender.
Moreover, a logic circuit is used to combine the bits hence to reduce the
probability of eavesdropping. The key obtained can be used to exchange the
information securely further it can help in encryption and decryption of
crucial data. Double level BB84 mechanism will help in information
reconciliation as well as privacy amplification. In future the proposed
mechanism will be very beneficial where unconditional security is required
during key and other secret information exchange
