Sreeparna Chakrabarti et al., International Journal of Advanced Trends in Computer Science and Engineering, 9(3), May – June 2020, 3910 – 3915 3910 ISSN 2278-3091 Volume 9, No.3, May - June 2020 International Journal of Advanced Trends in Computer Science and Engineering Available Online at http://www.warse.org/IJATCSE/static/pdf/file/ijatcse212932020.pdf https://doi.org/10.30534/ijatcse/2020/212932020 ABSTRACT The encryption process of Symmetric Key Cryptography is quicker as compared to Asymmetric Key Cryptography, but the key exchange process is a challenge. This paper focuses on Quantum Cryptography techniques for that purpose as traditional digital cryptography techniques are not safe. In "Quantum Key Exchange" Technique, "Heisenberg uncertainty principle" and "quantum no cloning theory" are used to resist attacks. The Quantum Key Exchange is demonstrated through BB84 algorithm and the result is analyzed. Discussion is made on the practical applications of the technique Key words: Quantum Key Cryptography, Quantum Key Exchange, BB84, Qubit. 1. INTRODUCTION Cryptography is the process or technique of securing the communication among several parties via some communication channel in the presence of a potential intruder. Among the two known techniques of cryptography viz. “Symmetric Key Cryptography” and “Asymmetric Key Cryptography”, the former demands the same key to be present with both the transmitter and receiver which gives rise to a big problem of secure key exchange. Additionally, millions of institutions like banks, hospitals, insurance companies etc. want to keep their stored data private too, for which they use Symmetric Key Cryptography as it is simpler and faster. Hence, they too need to transfer the key securely. Traditional way of transferring and securing the keys are not full proof however strong the algorithm might be. The existing cryptographic algorithms are established on the concept of finding out the factors of a very large integer.[5] An algorithm, which is proved to be secure enough today, can cease to be so tomorrow with the advent of stronger computational systems which may lead to the event of easily factorizing such numbers. RSA algorithm, which is a popular Asymmetric Key Algorithm, suffers from chances of attacks in the future like: factoring the key [9]. Even comparatively new and unique Cryptographic method like ScDs Pyramid [6] method needs the exchange of a common key which might be breakable in the future. Hence, with the progress of processing power of the systems, the traditional key exchange algorithms cannot be labelled as "Unbreakable Forever". This gave way to "Quantum Cryptography" where concepts of Quantum Physics are utilized to get a strong key exchange system which doesn't compromise the secrecy. A subset of it is the “Quantum Key Distribution System” which ensures safe exchange of Symmetric Key between the dispatcher and the receiver. 2. QUANTUM CRYPTOGRAPHY 2.1 Basic Concept In Classical Cryptography, bits(0 or 1) are used to encode the information, whereas in "Quantum Cryptography" (which is a subset of "Quantum Computing"), “quantum bits”(qubits) serve that purpose. A qubit is the lowest unit of quantum data like the two polarization states of a photon-horizontal and vertical. In classical system, 0 or 1 are the two possible states of a bit and the states cannot be combined. But in Quantum System, the qubit could be in a coherent superposition of both the possible states. Moreover, a qubit can hold more information than a bit. It has been proven that 2bits of data can be transferred via a single qubit using a process called "Superdense Coding". "Quantum Physics" is an area which deals with the particles that build up matter and studies about their interactions. "Quantum Cryptography" is based on dual pillars of "Quantum Physics": (i) The Heisenberg Uncertainty principle: "The momentum (p) and position (x) of a particle could not both be exactly Quantum Key Distribution: A Safer Alternate To Asymmetric Key Exchange Policies Sreeparna Chakrabarti 1 , Dr. G N K Suresh Babu 2 1 Research Scholar, Department of MCA, Visvesvaraya Technological University, Belgaum 1 Assistant Professor, Department of Computer Science, Kristu Jayanti College, Bengaluru chakrabartisreeparna@gmail.com 2 Professor, Department of ISE, Acharya Institute of Technology, Bengaluru gnksureshbabu@gmail.com