International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-3, Issue-4, April 2014 Quantum Cryptography using Quantum Key Distribution and its Applications N.Sasirekha, M.Hemalatha Abstract-Secure transmission of message between the sender and receiver is carried out through a tool called as cryptography. Traditional cryptographical methods use either public key which is known to everyone or on the private key. In either case the eavesdroppers are able to detect the key and hence find the message transmitted without the knowledge of the sender and receiver. Quantum cryptography is a special form of cryptography which uses the Quantum mechanics to ensure unconditional security towards the transmitted message. Quantum cryptography uses the distribution of random binary key known as the Quantum Key Distribution (QKD) and hence enables the communicating parties to detect the presence of potential eavesdropper. This paper also analyses few application areas of quantum cryptography and its limitations. Keywords- Classical Cryptography, Photon polarization, Qubit, Quantum Cryptography, Quantum entanglement, Quantum Key Fig 1: Communication in the presence of an Eavesdropper Distribution, Sifting key. I. INTRODUCTION Today, a technology known as Quantum key distribution (QKD) uses individual photons for the exchange of Cryptography is the practice and study of encoding and cryptographic key between the sender and the receiver. Each decoding secret messages to ensure secure communications. photon represents a single bit of data. The value of the bit, a 1 There are two main branches of cryptography: or a 0, is determined by states of the photon such as secret-(symmetric-) key cryptography and public- polarization or spin. With this method, one party can send a (asymmetric) key cryptography. A key is a piece of cryptographic key encoded with photons to another party. information (a parameter) that controls the operation of a The unique properties of photons as quantum objects are such cryptographic algorithm. In encryption, a key specifies the that any attempt to measure or to decipher the message will particular transformation of plaintext into cipher text, or vice change the photons' state. This uncertainty ensures that the versa during decryption. Keys are also used in other message will be destroyed or altered, making it easy for both cryptographic algorithms, such as digital signature schemes the sender and receiver to detect that the message has been and message authentication codes. In practice, due to compromised. Thus, QKD doesn't rely on preventing significant difficulties of distributing keys in secret key interception or decryption, but rather on detecting cryptography, public-key cryptographic algorithms are eavesdropping and self-destructing the message as a result. widely used in conventional cryptosystems. II. LITERATURE SURVEY Cryptographers make efforts to build more and more sophisticated means to obscure the sensitive information which is to be transmitted. But the hackers, code breakers, Smart cards, PINs, password authentication, etc., use current eavesdroppers work furiously to crack the systems. If either cryptographic techniques and they are performing well in cryptographers achieve security or the code breakers keeping data secure. However, the overall security of an decipher the security the success will be temporary. This encryption system relies in the ability to keep cipher keys process of securing the message using ciphering and breaking secret, but a typical human behavior is to write down the system using deciphering is an endless process. Once, this passwords either in their inbox of mobile phone or e-mail id, scenario is a chase in the race. this behavior makes security very vulnerable to attack. The concept of biometric-based keys seems to be one possible solution to this insecurity.[13] Security must be the primary consideration from a mission-critical or safety-related product’s conception, through design and development, production, deployment, and the end of its lifecycle.[18][19] Manuscript received on April 2014. Embedded systems that are installed in devices forms an N.Sasirekha, Department of Information Technology and Computer integral part of the manufacturing, health, transportation, and Technology, Rathinam College of Arts and Science, Coimbatore, finance sectors, as well as the military, without having Tamilnadu, India. M.Hemalatha, Department of Computer Science, Karpagam University, near-flawless strong cryptographic security built into them Coimbatore, Tamilnadu, India. might also be vulnerable to well organized crime, terrorists, Published By: 289 Blue Eyes Intelligence Engineering & Sciences Publication Pvt. Ltd. Quantum Cryptography using Quantum Key Distribution and its Applications or enemy governments. [14][18]-[20] measured to determine their orientation relative to one of Data hiding methodologies aim is to solve modern network these bases of polarization at a time. Classically, one would security, quality of services control, and secure expect the photon to have a certain polarization, which can be communications, is also a cost-effective alternative to other measured but which is not changed by the measurement. means of data security, which does not require protocol Photons, however, are quantum objects, which are modifications. This technology is compatible with existing considered to have a property only after it is measured. The standards of multimedia compression and type of measurement impacts the property of the object. This communications.[15] implies that a photon can only be considered to have a Security is an important aspect of any network, but in particular polarization after it is measure, and that the basis particular to mobile adhoc networks. The wireless networks chosen for the measurement will have an impact on the are potential for hacking using mobile devices. There is no polarization. clear line of defense for protecting the mobile neworks. The development of the Mobile Application Security System A. Process of Quantum Coding which uses a layered security approach and strong cryptographic techniques is seen as a feasible and low-cost solution to protect these application-based wireless Many algorithms of encoding and decoding information networks.[16] using a given key have been created already, many years Finally, a new concept in cryptographic security known as before quantum cryptography came into existence. Quantum Quantum Encryption, which uses quantum fluctuations of cryptography is not replacing traditional cryptography but it laser light at the physical layer introduced into existing allows for a more secure transfer of the keys used in encoding networks. It enables ultra-secure communications and near and decoding. The maximum speed, scale and security of the perfect security. [17] transfer is achieved by sending the secret key using quantum coding, but encoding and sending the data itself using traditional methods and algorithms. Quantum cryptography was first proposed by Stephen Weisner in his work "Conjugate Coding" in the early 1970s. Quantum Information Processing and Quantum Bit Conjugate coding is an extension of Random number generator. [1] In Sigact News, a proposal was published in Quantum information processing or quantum information the year 1983, and at that time two scientists Bennet and science is an interdisciplinary field. It is an amalgamation of Brassard, who were familiar with Weisner's ideas, were ready quantum physics, information science engineering, computer to publish their own ideas. In 1984, they produced the science, mathematics and chemistry. "BB84” which is the first quantum cryptography protocol. [7] A bit; a binary digit, is the base of classical information In 1991, the first experimental prototype based on this theory. Regardless of its physical representation, it is always protocol was produced which operated over a distance of 32 read as either a 0 or 1. For instance, a 1 (true value) is centimeters. During that period, the technology has been refined and the distance may be increased to kilometers. [3], represented by a high voltage, while a 0 (false value) is represented by a low voltage. A quantum bit, or qubit [6] (sometimes qbit) is a unit of quantum information. In quantum cryptography, two process are carried out. They are In June 2003, a team at the University of Vienna transmitted conversion and polarization. That means the data is converted entangled photons across the river Danube, through free to bits of 0s and 1s, which are then transferred using polarized space. In April 2004, the first money transfer encrypted by photons. Photons are placed into a particular quantum state quantum keys was experimented between the two Austrian by the sender which will be observed by the receiver. banks. These two buildings were 500 meters apart, and fibre A photon can be in one of four polarizations: optics was fed through 1.5 kilometers of sewage system to 90, 0, 45 and -45 degrees link them together. [5] A photon is measured using three different bases: rectilinear (horizontal or vertical), circular (left-circular or III. QUANTUM CRYPTOGRAPHY right-circular), and diagonal. The receiver can distinguish the polarization of the photons between a 0 and 90 degrees Quantum cryptography [10],[11]solves the problems of polarizations, or -45 and 45 degrees polarizations. secret-key cryptography by providing a way for two users who are in different locations to securely establish