Abstract:
Quantum Key Distribution Protocol (QKD) is a type of quantum cryptography, i.e., it uses the concepts related to quantum mechanics to establish
security in the communication channel. It is a key generation protocol and is
used for generating a shared secret key between two parties, commonly known
as Alice and Bob. Any QKD protocol uses two communication channels for
the key generation. The first one is a quantum channel for the transmission
of qubits. The other one is a classical channel for the transmission of random classical bits. The two major processes of any QKD protocol involve
key generation algorithm and classical post processing phase. For the key
generation process, algorithms like BB84 protocol or Eckart E91 protocol is
used. These algorithms use polarisation, entanglement, and measurement
concepts of quantum mechanics for generating the key. The key generated
in the final step of the key generation algorithm of the QKD protocol is
made up of classical bits. Because of the inherent noisy nature of quantum
channels, the keys generated at both ends after classical reconciliation can
still be wrong. This defeats the purpose of key sharing. To overcome this
adversities classical post processing is used. In this phase the keys generated
at the two ends are processed via an error correcting scheme to potentially
reach a common key without any public sharing of the data. To this end
we have studied the behavior of various error correction schemes, both block
based and convolutional schemes and later used them as part of the post
processing phase of the BB84 QKD protocol. Then we studied the efficiency
of these coding schemes with and without the interruption of a malicious
third party.
