Most cryptographic mechanisms, such as symmetric and asymmetric cryptography, often involve the use of cryptographic keys. However, all cryptographic techniques will be ineffective if the key distribution mechanism is weak. The security of most modern cryptographic systems of key distribution mechanism is based on computational complexity and the extraordinary time needed to break the code. Qua...

This report summarises the ongoing work in QuComm on the demonstration of novel quantum communication protocols, in particular multi-party protocols or protocols which use more than 2-states (or more than one qubit). Such new protocols will extend the capabilities of quantum communication by increasing the channel capacity, by making the systems less sensitive to channel noise. Examples of such...

Quantum information processing (QIP) is a field concerned with technological applications of quantum mechanical phenonomena. In many cases, photons are an ideal quantum system for such applications. Photons exhibit superb coherence properties, are robust to environmental noise, and can be transmitted over long distances. One of the main difficulties of photon based quantum information processin...

Classical cryptography algorithms are based on mathematical functions. The robustness of a given cryptosystem is based essentially on the secrecy of its (private) key and the difficulty with which the inverse of its one-way function(s) can be calculated. Unfortunately, there is no mathematical proof that will establish whether it is not possible to find the inverse of a given one-way function. ...

Quantum cryptography is an approach to securing communications by applying the phenomena of quantum physics. Quantum cryptography provides secure communication whose security depends only on the validity of quantum theory. Interesting characteristics of quantum mechanics includes the existence of indivisible quanta and of entangled systems, both of which lie at the root of the quantum cryptogra...

Quantum cryptography is on the verge of commercial application. One of its greatest limitations is over long distance—secret key rates are low and the longest fibre over which any key has been exchanged is currently 100 km. We investigate the quantum relay, which can increase the maximum distance at which quantum cryptography is possible. The relay splits the channel into sections and sends a d...

This is a chapter on quantum cryptography for the book “A Multidisciplinary Introduction to Information Security” to be published by CRC Press in 2011/2012. The chapter aims to introduce the topic to undergraduate-level and continuing-education students specializing in information and communication technology.

Lectures on classical and quantum cryptography. Contents: Private key cryp-tosystems. Elements of number theory. Public key cryptography and RSA cryp-tosystem. Shannon's entropy and mutual information. Entropic uncertainty relations. The no cloning theorem. The BB84 quantum cryptographic protocol. Security proofs. Bell's theorem. The EPRBE quantum cryptographic protocol.

Quantum Cryptography was born in the early seventies when Stephen Wiesner wrote “Conjugate Coding”, which unfortunately took more than ten years to see the light of print [50]. In the mean time, Charles H. Bennett (who knew of Wiesner’s idea) and Gilles Brassard picked up the subject and brought it to fruition in a series of papers that culminated with the demonstration of an experimental proto...