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Quantum Cryptography: A Step Towards Secure
Communications
Hitendra Singh Rathore, Dhairya Bharadwaj
B Tech 3rd^ year (CSE) SKIT, Jaipur
Abstract
Quantum cryptography is a newly emerging technology which can ensure ultimate
security in domain of communications. In common cryptographic approaches we are
more focused on protecting our information via the mathematical methods, it’s the
place where quantum cryptography exceeds it as it diverts its methods from
mathematical to physical laws making it somewhat impenetrable. The working of
quantum cryptography depends on elements of quantum computing like the Heisenberg
principle of uncertainty and the principle regarding photon polarization. This paper is
focused mainly over the principle of quantum cryptography and outlines the real life
components associated with it, along with the future direction quantum cryptography is
progressing.
Keywords : Quantum cryptography, communication security
1. Introduction
Nowadays, communications over a large distance plays a crucial role in our daily lives. Secure communications had developed great implementation in many areas, e.g., online purchases, emails and video chats. Cryptography is about the designing and analysis of mathematical methods that enable secure communications when there is a presence of malicious adversaries. The main aim is to send information to the desired receiver without giving any information to a third party.[1]. It is a science of protecting information by encoding it into a format which is unreadable without any proper decryption.[2] The problems with conventional computing methods is that we put our faith in the math involved behind the encryption system, that can be easily exploited by using superior computing powers or clever mathematics it means it is not that secure as we assume it to be. In search of a more secure method of protection from code breakers, a new generation of code makers has been turning
from mathematics to physical laws which are unbreakable. Experts in atoms and other subatomic entities, these cryptologists want to exploit the laws of quantum mechanics used in quantum computing in terms of qubits to send messages that are provably unhackable.[3] Based on the laws of physical world, quantum cryptography allows exchange of cryptographic codes between two remote users providing unquestionable security. The foundation of quantum cryptography lies on the Heisenberg principle of uncertainty, which ensured that as certain pairs of physical properties are related in a way that measuring one property prevents the observer from simultaneously getting the information about the value of the other.[4] It uses quantum states of photons to transfer security key required for decryption using polarised photons (photons whose rotation is controlled) to represent bits 0 or 1. Each photon, better known as Qubits, carries one bit of quantum information. To understand those qubits, the recipient must determine the photon's exact polarisation. The act of an eavesdropper batting an eye on a photon in this transmission will irretrievably change or modifies the information encoded on that photon, thereby detecting any flaw in the security.[5] Quantum cryptography has great potential to become a very important technology for securing safety and privacy of communication in the future computing world and thus to become the driver for the success of an array of services.
2. Literature Review
Colombia University at New York, in early 1970’s but his work was first published 1983 in SIGACT news. Two other scientists Bennet and Brassard having knowledge of Wiesner’s works stipulated their own theories and issued a cryptography protocol called “BB84”6+ in 19847+. In 1992 Bennett published a “minimal” QKD scheme called “B92” and proposed that it could be implemented just by using single- photon’s interference with photons propagating for long distances by using optical fibers. [8] Since then, several experimental groups have developed optical fiber- based QKD systems the first experimental prototype was functioning for a range of 32cm which has been improved for a distance of around few kilometers. A complete computer network up and running which is completely based on quantum cryptography at Cambridge, Massachusetts. After that a team at the University of Vienna used it to transfer entangled photons across the river Danube, through atmosphere in June 2003. In April 2004, the first money transfer encrypted by quantum keys was initiated between two Austrian banks. The two buildings were
quantum channel which than bob will check for his generated sequence and assign “pass” or ”fail ” for each bit received. As an example say for Alice “0”<-> V “1” <- + And for Bob random bit sequence to be somewhat like “0” <- - 45 “1” <-> H Thus a sample for 4 bits the output can be like Alice’s number 1 0 1 0 Alice’s polarisation +45 V +45 V Bob’s polarisation - 45 - 45 H H Bob’s number 0 0 1 1 Bob’s result Fail Fail Pass Fail In this experiment we see that for the first and last bit Alice and Bob had different bit
values, so that Bob’s output is “Fail” in both the cases. However, for the second and
third bits, Alice and Bob have the same bit result and the protocol is such that there
is a chance of 0.5 that Bob’s result is a “Pass” in each case. Of course, we cannot
decide in any particular experiment which one will be declared “Pass”, but in this
example second bit was a “Fail” and the third bit was a “Pass”.[12]
Figure: a view of optical fiber quantum cryptography experiment at LOS ALMOS lab.
The two boxes in the foreground contain Alice’s interferometer (box on left) and Bob’s interferometer. The overhead optical fibers convey photons from Alice’s control system (leftmost workstation at right rear) to Alice’s interferometer, then out to the 48-km fiber network, back into Bob’s interferometer and then to Bob’s single photon detectors located in the refrigerator to the right of Bob’s workstation (adjacent to Alice’s workstation). Although physically co-located there are no direct electrical or optical connections between Alice’s and Bob’s systems.
4. Limitations of Quantum Cryptography
Contrary to practical assumptions that it requires a single optical fiber for transmission, the fact is that splicing and connection provide no problem at all in the procedure. Also the process completely supports WDM (wavelength division multiplexing) but to implement it requires a much sophisticated network design to be implemented. The only shorthand in this whole procedure is that is does not support any intermediate amplifiers in the circuit carrying the quantum signal. As such a device will modify the data as a eavesdropper will and will render the process useless. This implies to a fact that range of this type of communication is limited, commercial implementations have shown a vitality of 100km while research models were designed for about 250km [13]. Another noticeable problem with this method is that It requires a direct optical link between sender and receiver, rendering it to be a specific point-to-point method of communication, However, it is possible — as demonstrated by the Swiss Quantum project to build a key management layer on top of quantum cryptographic equipment to route and relay keys securely across meshed networks.[14]
5. Ongoing research in Quantum cryptography
Since the first practical model developed for a successful transmission achieved for few centimeters, continuous efforts are being done to improve that prototype. The major institutions in these enhancements include Los Alamos National Laboratory in New Mexico, the UK Defense Evaluation and Research Agency, and at the University of Geneva at Switzerland [15]. These institutes have worked in pushing quantum cryptography out of its limits. There have been efforts to achieve quantum transmission via atmospheric transmission and optical cables, so as to make this technology fruitful for a large variety of customers including cities, businesses, military organizations, and government sites. As a result of all these efforts in this field of technology have led to improvements in the quality and speed of transmission, like the laser assisted technology in photon identification helps to achieve a enhanced speed of transmission. Alongside the fiber communications
