Quantum cryptography, or more correctly named, Quantum Key Distribu- tion (QKD), uses the theory of quantum mechanics to secure the informa- tion, by generating a secret, random key between the two parties over an insecure communication channel. QKD is based on two fundamental princi- ples of quantum mechanics, namely the Heisenbergs Uncertainty Principle and the Superposition Principle. The securely distributed key is used to implement a one-time pad encryption scheme. Since the key is used only once and is completely random, it cannot be predicted beforehand by the sender, receiver or eavesdropper. The major advantage of QKD is that the one-time pad encryption scheme provides unconditional security over an insecure communication channel. The CQT is currently developing a QKD system for low-cost applications as well as investigating new QKD proto- cols. The cryptographic system is designed for the transfer of quantum information through the use of phase-encoded single photons over optical fibre.
The critical nature of secure communication in our society has prompted CQT to explore beyond a two-node QKD setup. Quantum networks facili- tate QKD ’on-demand’ between two arbitrary network users. They consist of a number of hybrid quantum channels integrated to form a complete net- work. This is essential for the optimization of network throughput as some quantum channels are better suited to particular terrains. There is also greater robustness against Denial of Service attacks due to redundant light paths within a network. This also assists in the reduction of key relation knowledge by any adversary. A vast number of topologies are currently being envisaged, many based on present day network topologies. This will allow for transparent integration into current networks. These networks will, at present, be valuable to the finance and communication sectors; however with the continuous improvements of computational power and the inadvertent realization of the Quantum Computer, QKD will become necessary for any form of secure data transfer, thus paving the way for the development of Quantum Cities and national and international Quantum Grids.