Quantum cryptography was designed to provide a new approach to the problem of distributing keys for private-key cryptography. The principal idea is that security can be ensured by exploiting the laws of quantum physics and, in particular, by the fact that any attempt to measure a quantum state will change it uncontrollably. This change can be detected by the legitimate users of the communication channel and so reveal to them the presence of an eavesdropper. In this paper I explain (briefly) how quantum key distribution works and some of the progress that has been made towards making this a viable technology. With the principles of quantum communication and quantum key distribution firmly established, it is perhaps time to consider how efficient it can be made. It is interesting to ask, in particular, how many bits of information might reasonably be encoded securely on each photon. The use of photons entangled in their time of arrival might make it possible to achieve data rates in excess of 10 bits per photon.
Quantum cryptography was designed to provide a new approach to the problem of distributing keys for private-key cryptography. The principal idea is that security can be ensured by exploiting the laws of quantum physics and, in particular, by the fact that any attempt to measure a quantum state will change it uncontrollably. This change can be detected by the legitimate users of the communication channel and so reveal to them the presence of an eavesdropper. In this paper I explain (briefly) how quantum key distribution works and some of the progress that has been made towards making this a viable technology. With the principles of quantum communication and quantum key distribution firmly established, it is perhaps time to consider how efficient it can be made. It is interesting to ask, in particular, how many bits of information might reasonably be encoded securely on each photon. The use of photons entangled in their time of arrival might make it possible to achieve data rates in excess of 10 bits per photon.
The practical implementation of quantum information technologies requires, for the most part, highly advanced and currently experimental procedures. One exception is quantum cryptography, or quantum key distribution, which has been successfully demonstrated in many laboratories and has reached an advanced level of development. It will probably become the first commercial application of quantum information. In quantum key distribution, Alice and Bob exploit a quantum channel to create a secret shared key comprising a random string of binary digits. This key can then be used to protect a subsequent communication between them. The principal idea is that the secrecy of the key distribution is ensured by the laws of quantum physics. Proving security for practical communication systems is a challenging problem and requires techniques that are beyond the scope of this book. At a fundamental level, however, the ideas are simple and may readily be understood with the knowledge we have already acquired. Quantum cryptography is the latest idea in the long history of secure (and not so secure) communications and, if it is to develop, it will have to compete with existing technologies. For this reason we begin with a brief survey of the history and current state of the art in secure communications before turning to the possibilities offered by quantum communications. The history of cryptography is a long and fascinating one. As a consequence of the success or, more spectacularly, the failure of ciphers, wars have been fought, battles decided, kingdoms won, and heads lost. In the information age, ciphers and cryptosystems have become part of everyday life; we use them to protect our computers, to shop over the Internet, and to access our money via an ATM (automated teller machine). One of the oldest and simplest of all ciphers is the transposition or Caesarean cipher (attributed to Julius Caesar), in which the letters are shifted by a known (and secret) number of places in the alphabet. If the shift is 1, for example, then A is enciphered as B, B→C, · · ·, Y→Z, Z→A. A shift of five places leads us to make the replacements A→F, B→G, · · ·, Y→D, Z→E.
The interest in quantum-based security methods has been growing rapidly in recent years. New implementations of quantum key distribution and new network services supported by this solution are being introduced. The reason behind the growing popularity of quantum cryptography is its unrivaled security level: all eavesdroppers can be revealed through the application of the laws of physics. First of all, the rules of quantum mechanics ensure that any measurement modifies the state of the transmitted quantum bit. This modification can be discovered by the sender and the receiver. This makes passive eavesdropping impossible. Using protocols such as BB84, network users are able to send a string of bits coded by the polarized photons. After that, they can establish secure cryptographic keys through an unsecure channel using different key distillation methods. Major ongoing challenges include the control and management of security in systems using quantum cryptography, as well as tailoring security to specific end user's requirements and services.
Quantum Cryptography is a novel approach to make the information and network world more secure. Unlike classical cryptography, quantum cryptography ensures the security of communication because it is based on the laws of Quantum Mechanics; a branch of physics that deals with the fundamental behavior of matter and their energies to the levels of subatomic particles. These particles and their intrinsic properties such as photon polarization and entanglement allow us to develop an unbreakable system of cryptographic information. Conventionally, the security has been primarily concerned with the secured distribution of secret key carried over an insecure channel. However, in Quantum Cryptographic systems the transmission of secret key is done using aforementioned laws of nature through a secured quantum channel highly susceptible to intrusion detection. Consequently, the Quantum Key Distribution (QKD), in conjunction with protocols such as BB84 protocol has emerged as an ultimate modern secured communication system. This article concentrates on briefly reviewing quantum cryptography, some recent developments and reports of its vulnerabilities.
Cryptography used to be of interest only to spies and the security services. However, the rise of e-commerce means that everyday actions, such as withdrawing cash from ATM machines or buying goods on the Internet, are mediated by cryptographic techniques that would be the wonder of WWII code breakers. The widespread deployment of such techniques shows that they are basically sound. However, all these cryptographic techniques rely on keys and ensuring the security of these keys is a problem. Quantum cryptography (QC) is a technique for distributing keys in a way that would provide, in theory at least, total protection against hackers and eavesdroppers. The basic principle is to encode the 0s and 1s of a classical cryptography key on the polarisation state of individual photons. An eavesdropper attempting to 'read' one of these photons risks changing its polarisation state, thus revealing his/her presence. As this idea depends on creating an optical link operating at the single photon level, barriers to its implementation were considerable. Progress has been steady and transmission distances over fibre now exceed 100 km. The article looks at the latest developments in QC.
The quantum cryptography approach is a significant change in secure communication in the sense that quantum cryptography bases its security on the law of quantum physics as opposed to computation difficulty. With classical encryption methods rapidly losing their resistance to the power of the underlying computers as well as the expected possibilities of the quantum computers, quantum cryptography comes into the limelight as a possible method of securing information in the long term. The paper is a detailed and systematic review of quantum cryptography along with the fundamentals of this practice, the way it works, and its practical implementation. It describes the ability of quantum phenomena to be unique (including superposition, uncertainty, and disturbance of measurement) and able to secure a key exchange as well as ensure any attempt of eavesdropping would be automatically noticed.In the review, the authors mainly discuss quantum key distribution (QKD) protocols, their functioning principles, security assurances, and the benefits of quantum over classical key exchange schemes. Besides that, the paper critically evaluates the real issues surrounding the implementation of quantum cryptographic systems such as hardware limitations, transmission range, environmental noise, and compatibility, to existing compatibility infrastructures. Recent advances in the field of experiments and pilot implementations are presented to determine the maturity of new technologies, and their suitability to be used on a large scale. Through its analytical review of theoretical assets, as well as practical constraints, this paper offers a definite and equalist view of the state of quantum cryptography today and also explains the research priorities important in its scale, moving away of the test production systems to the dependable and extensive security measures.
Classical cryptography is the process of hiding information and it manages the secret knowledge by encrypting the plain text message through the translation of it to an unintelligible message. Quantum cryptography is also hiding the plain text through encryption and it works based on the law of quantum physics for providing absolute security of data communication. It uses the idea of quantum mechanics to gadget a cryptographic system and the key problems are solved by intrusion detection including the Eavesdropping detection using quantum expertise. On the contrary, principles of secured communication protocol systems are demonstrated with classical quantum cryptography where the keys are distributed securely and are applied in quantum key distribution as well. In this paper, we provide a survey of works on classical cryptography and quantum cryptography and compare them with respect to time, security level and the classification of the data. Moreover, we perform a concise analysis of perspective classical cryptography and the conception of Quantum cryptography with various protocols and highlight the benefits of classical cryptography and Quantum cryptography in different applications. Finally, we provide a set of recommendations for selecting the suitable encryption model for securing the communication.