Quantum Cryptography and Quantum Key Distribution Protocols: A Survey Abstract— Quantum cryptography renders a cryptographic solution which is imperishable as it fortifies prime secrecy that is applied to quantum public key distribution. It is a prominent technology wherein two entities can communicate securely with the sights of quantum physics. In classical cryptography, bits are used to encode information where as quantum cryptography i.e. quantum computer uses photons or quantum particles and photon’s polarization which is their quantized properties to encode the information. This is represented in qubits which is the unit for quantum cryptography. The transmissions are secure as it is depended on the inalienable quantum mechanics laws. The emphasis of this paper is to mark the rise of quantum cryptography, its elements, quantum key distribution protocols and quantum networks. Index Terms— basis, classical cryptography, photons, polarization, quantum cryptography, quantum key distribution protocol, qubits, quantum networks, states I. INTRODUCTION The principle of uncertainty could be used for cryptography was first devised by Stephen Wiesner, a physicist in 1969 [1]. Thus the hatching of quantum cryptography took place which has given a promising concept to many cryptographers. One of the ideas of [1] was expanded to propose a method for quantum public key distribution i.e. QPKD under the principles of quantum mechanics which is verifiably secure [2]. Bennet and Brassard who had collaboration with Stephen Wiesner were proposed the first QPKD in 1984 and is familiarized as the BB84 protocol [4]. Quantum cryptography is a prominent technology wherein two entities can communicate securely by implementing the sights of quantum physics. QPKD commences with the transmission of photons which are prepared in four quantum states randomly, relating to two mutually conjugate bases [1], rectilinear and diagonal. The rectilinear basis has two states i.e. polarizations namely 0° represented horizontally and 90° represented vertically. The diagonal basis 45° and 135° [1] [4]. The transmissions are secure as it is depended on the inalienable quantum mechanics laws. The two predominant constituents of quantum mechanics i.e. the principle of Heisenberg Uncertainty and the principle of photon polarization are the foundations of quantum cryptography. The Heisenberg Uncertainty principle defines that the observer simultaneously cannot measure two physical properties which are related with each other [4]. In regard to this definition, two examples are referred 1) the example which is customarily specified is, where for a particle P, the position A and the momentum B of P cannot be calculated simultaneously. 2) The measurement of a photon cannot be done simultaneously in rectilinear basis and diagonal basis [1] [2]. If done, it randomizes the other. The principle of photon polarization defines that the replica of qubits cannot be made as per theorem of no-cloning [1] [3]. It was recognized that photons were used for transmitting the information instead of storing it which was the major revolution in the area of quantum cryptography [5]. Section 2 gives an outline about Quantum Cryptography. Section 3 discusses about the probability of a photon transmitted and produced. Section 4 explores about quantum key distribution protocols. Section 5 discusses about quantum networks. Section 6 outlines about recent contributions in this area. Finally section 7 gives a conclusion and future enhancement. II. QUANTUM CRYPTOGRAPHY A. Polarization of Photon The photon is polarized in one of the bases to represent a bit known as a qubit. A 0° polarization of photon in the rectilinear Ms. V. Padmavathi Associate Professor Sreenidhi Institute of Science and Technology Hyderabad, Ghatkesar, Telangana India chpadmareddy1@gmail.com Dr. B. Vishnu Vardhan Professor JNTUH College of Engineering Karimnagar, Telangana, India mailvishnu@yahoo.com Dr. A. V. N. Krishna Professor & Head Navodaya Institute of Science and Technology Raichur, Karnataka India hari_avn@rediffmail.com 2016 6th International Advanced Computing Conference 978-1-4673-8286-1/16 $31.00 © 2016 IEEE DOI 10.1109/IACC.2016.109 545 2016 6th International Advanced Computing Conference 978-1-4673-8286-1/16 $31.00 © 2016 IEEE DOI 10.1109/IACC.2016.109 545 2016 IEEE 6th International Conference on Advanced Computing 978-1-4673-8286-1/16 $31.00 © 2016 IEEE DOI 10.1109/IACC.2016.109 545 2016 IEEE 6th International Conference on Advanced Computing 978-1-4673-8286-1/16 $31.00 © 2016 IEEE DOI 10.1109/IACC.2016.109 556 2016 IEEE 6th International Conference on Advanced Computing 978-1-4673-8286-1/16 $31.00 © 2016 IEEE DOI 10.1109/IACC.2016.109 556