QUANTUM CRYPTOGRAPHY ABHINAV GUPTA CSc 8230

Introduction [1,2]  Quantum cryptography is an emerging technology in which two parties can secure network communications by applying the phenomena of quantum physics.  The appealing characteristic of quantum cryptography is the possibility of distributing secret key between two users in a manner that it is impossible for a third party to eavesdrop without changing the quantum transmission and hence the eavesdropping is detected by users

BB84 Protocol [1,3]  The sender (traditionally referred to as Alice) and the receiver (Bob) are connected by a quantum communication channel which allows quantum states to be transmitted.  In addition they communicate via a public classical channel.  This protocol encodes the information in pair of non-orthogonal states.  The usual polarization state pairs used are either the rectilinear basis of vertical (0°) and horizontal (90°), the diagonal basis of 45° and 135°(-45).

BB84 Protocol Contd.. [3,4]  Alice creates a random bit (0 or 1) and then randomly selects one of her two basis to transmit it in.  She then prepares a photon polarization state depending both on the bit value and basis.  Alice then transmits a single photon in the state specified to Bob, using the quantum channel.  This process is then repeated.  Bob does not know the basis the photons were encoded in, so select a basis at random to measure in.  After receiving all photons Bob communicate Alice on public channel.  Alice broadcasts the basis each photon was sent in, and Bob the basis each was measured in.

BB84 Protocol Contd.. [3,4]

 To check for the presence of eavesdropping Alice and Bob now compare a certain subset of their remaining bit strings.  If a third party (Eve) has gained any information about the photons' polarization, this will have introduced errors in Bobs' measurements.  If more than p bits differ they abort the key and try again.  p is chosen so that if the number of bits known to Eve is less than this, privacy amplification can be used to reduce Eve's knowledge of the key to an arbitrarily small amount, by reducing the length of the key.

Using Quantum Cryptography for securing Wireless LAN networks, 2009 International Conference on Signal Processing Systems[5] MIC – message integrity code Here telecommunication is not based on the optical-fibers but rely on free space line-of-sight-communication systems. Paper suggest how we can integrate Quantum key distribution in i (WLAN), by modifying the 4-way handshake to integrate the BB84 protocol as presented:

Implementations [2,3]  There are currently four companies offering commercial quantum cryptography systems; id Quantique (Geneva), MagiQ Technologies (New York), SmartQuantum (France) and Quintessence Labs (Australia).  Quantum encryption technology provided by the Swiss company Id Quantique was used in the Swiss state of Geneva to transmit ballot results to the capitol in the national election occurred on Oct. 21, (Shows how secured method it is)  The world's first computer network protected by quantum cryptography was implemented in October 2008, at a scientific conference in Vienna. The network used 200 km of standard fibre optic cable to interconnect six locations across Vienna and the town of St Poelten.

References [1]10th INTERNATIONAL CONFERENCE AND SEMINAR EDM'2009, SECTION III, JULY 1-6, ERLAGOL Quantum Cryptography Vladimir L. Kurochkin, Igor G. Neizvestny Institute ofSemiconductor Physics, Siberian Division, RAS, Novosibirsk, Russia [2]2009 Sixth International Conference on Information Technology: New Generations, Quantum Cryptography: A New Generation of Information Technology Security System by Mehrdad S. Sharbaf. [3] [4] Bennett, Ch. H., & Brassard, G., ”Quantum cryptography: public key distribution and coin tossing”, IEEE Conference on Computer, Systems, and signal Processing, 1984 [5]2009 International Conference on Signal Processing Systems “Using Quantum Cryptography for securing Wireless LAN networks” by A.Falahati, Hadi Meshgi

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