Quantum cryptography: Latest security measure for network communication
Neha Yadav Dr. Alka
Department of information technology Department of information technology
Baba Saheb Bhimrao Ambedkar university Baba Saheb Bhimrao Ambedkar university
Lucknow, India Lucknow, India
Abstract:This research paper focuses on the origin and concept of quantum cryptography, and how quantum cryptography will prove to be beneficial for security in network communication. It briefs the present state of quantum cryptography, and its practical applications, and at end the future aspects of quantum cryptography.
Quantum cryptography is a latest technique, which is used to ensure the secrecy of information transferred between two parties, usually called Alice and Bob, by applying phenomenon of quantum physics.In the late sixties Wiesner originated the first application of quantum information theory . He suggestedto make unforgeable currency notesby using the spin of particles. Following the tracks of Weisner\'s idea, in 1984 Bennett and Brassard proposed a protocol to distribute secret keys using the principles of quantum mechanics called quantum cryptography or more precisely quantum key distribution . The method of quantum cryptography depends mainly on two important elements of quantum mechanics- Heisenberg Uncertainty principle [3,4,5] and photon polarization principle. In quantum mechanics the Heisenberg\'s uncertainty principle or Heisenberg\'s indeterminacy principle states that any of a variety of mathematical inequalities asserting a fundamental limit to the precision with which certain pairs of physical properties of a particle, known as complementary variables, such as positionand momentum could be known. Measuring one property will always affect other property of the particle, so it\'s not possible to measure all the properties of particle exactly at the same time. The photon polarization principle states that, an eavesdropper could not duplicate unknown qubits i.e. quantum states that are not known, because of no-cloning theorem which was first presented in 1982 by Wootters and
Cryptographers have found number of intelligent means to transmit secure data using encryption,from seventies till now, Specifically, classical ciphers encrypt messages using a small secret key, which is much smaller than the message. This makes confidentiality achievable in practice. From Claude Shannon\'s theory  of 1949 we know that the confidentiality of such schemes cannot be hundred percent.So by exploring the counter-intuitive properties of quantum mechanics, they developed a method to exchange a secret key whose secrecy is insured by the principles of physics, this method is called quantum cryptography. In quantum cryptography, following the uncertainty principle, an eavesdropper cannot know everything about a photon that carries a key bit and will destroy a part of the information. So, eavesdropping stimulates errors on the transmission line, which can be caught by Alice as well as Bob. Current technologies, such as commercially available lasers and fiber optics can be used to achieve quantum cryptography Furthermore, Shannon\'s condition on the secret key length no longer poses any problem, as one can use quantum key distribution to obtain a long secret key and then use it classically to encrypt a message of the same length. By removing the hardship of secrecy of transferring lengthy keysthe uncertainty principle finds a positive application.Furthermore, quantum key distribution guarantees long-term secrecy of confidential data transmission. Secrets are encrypted at present by using classical ciphers canbecome unlawfully decryptable in the next ten years. There is nothing that prohibits an eavesdropper from intercepting an encrypted classical transmission and keeping it until technology makes it possible to crack the encryption. Moreover, the key obtained using quantum key distribution could not be copied. Attacking the key means attacking the quantum transmission at present, which can only be done by using current technology.
2. Quantum key distribution (QKD)
Quantum key distribution (QKD) is an approach that allows two parties, conventionally called Alice, Bob, to share a common secret key for cryptographic purposes. To make sure the secretly of communications, Alice Bob agree on a same, yet confidential, and that piece of information called a key. Encryption is carried out by combining the message with the key in such a manner that the result is incomprehensible by an observer who knows the key. The recipient of the message use copy of the key to decrypt the message.Let us persist that it is not the purpose of QKD to encrypt data. Instead, the aim of QKD is to guarantee the secrecy of a distributed key. The legitimate parties may use this key for encryption. The secrecy of the transmitted data is then ensure by two links: the quantum-distributed key and the encryption algorithm. If out of two one is broken, the whole chain is compromised; hence we have to look at the strengths of both links.First, in what way the confidentiality of the key ensured? The laws of quantum mechanics have unusual properties, with the good consequence of making the eavesdropping detectable. If an eavesdroppertries to discover the key, she will be detected. The legitimate parties will then toss out the key, while no secret information has been transmitted yet. If, on the other hand, no tapping is discovered as the secrecy of the distributed key is guaranteed.As the second link, the encryption algorithm must also have vigorous properties. As described above, the secrecyof data is absolutely guaranteed if the encryption key is as long as the message to transmit and it cannot be used again for subsequent messages. This is where quantum key distribution is specifically useful, as it can distribute long keys as often as needed by Alice and Bob.
Now lets see how QKD works. Quantum key distribution needs a transmission channel on which quantum carriers are transferred from Alice to Bob. In theory, those particle obeying the laws of quantum mechanics can be used. In practice, although, the quantum carriers are normally photons, the elementary particle of light, while the channel may be an optical fiber.In the quantum carriers, Alice encodes random bits of information that will make up the key. These pieces of information may be, for example, random bits or Gaussian-distributed random numbers, but for simplicity of the current discussion, let us obstruct us to the case of Alice encoding only zeroesand ones. Point out that what Alice sends to Bob may not be meaningful. The whole point is that an eavesdropper cannot guess any of the transmitted bits.
During the transmission between Alice and Bob, Eve might listen to the quantum channel and as a result spy on potential secret key bits. This does not pose a main issue to the legitimate parties, as the eavesdropping is detectable by way of transmission errors. Furthermore, the secret-key distillation techniques allow Alice and Bob to overcome from such errors and establish a secret key out of the bits that are unknown to Eve.
After the transmission, Alice and Bob can equate a fraction of the exchanged key to see if there are any transmission mistakes caused by eavesdropping. For this procedure, QKD needs the use of a public classical authenticated channel, as depicted in Fig. 1 This classical channel has two important features, namely, publicness and authentication. It is not needed to be public, but if Alice and Bob had gone though to a private channel, they would not need to encrypt messages; hence the channel is presumed to be public. As an important result, any message interchanged by Alice and Bob on this channel may be known to Eve. The authentication feature is important so that Alice and Bob can ensure that they are speaking to each other. We may think that Alice and Bob familiar to each other and will not get fooled if Eve acts to be either of them.The most successful implementation of QKD, BB84, falls into the first category, which is named after Bennett and Brassard, BB84 uses photon polarization states to transfer data from sender to source. The sender selects two interrelated states, each described by two bases. By the Heisenberg uncertainty principle, which states that it is not possible to measure two interdependent physical quantities altogether, only one of the two states can be known.
For each and every photon, the sender chooses a random bit (0 or 1), and one of the two bases that brief the state, and considering the state of the photon based on both of these random choices. The recipient must also arbitrary choose a basis in which to calculate the photon, and when the sender and recipient use the same basis, they will observe the same state. The outcome string of shared choices becomes their key, and the rest of the photons are discarded.
Fig. 1Quantum key distribution comprises a quantum channel and a public classical authenticated channel. As a universal convention in quantum cryptography, Alice sends quantum states to Bob through a quantum channel. Eve is suspected of eavesdropping on the line.
3.Current status of quantum cryptography
The researchers still doing the research that how we can use the quantum computer that make cryptographic system unbreakable. Based upon the difficulty of computing a specific mathematical problem, the current public key system like RSA  and ECC  are depended in security. Basically, quantum cryptography is based on the fact that how it can evaluate those mathematical problems which are difficult to compute. The mathematical problems which are difficult to evaluate are called trapdoor functions. It is so, because it is not difficult from working in one set of values but when we worked in reverse by deriving the solution from the set of values becomes a difficult task. Finding the set of values from which trapdoor solution was generated fromshouldare difficult to guess right, as it would be to resolve. Given that the chances of assuming a big number correct are practically zero, the possibilities of finding the solution would be practically zero. If there is no algorithm to fasten the process, estimating the solution would reduce to calculatingall possible solutions and testing whether the guess is correct. These problems can geared up by a quantum computer using Groverâ€™s algorithm. Therefore, it is likely that these new public key algorithms would be safe and secure from breaking using quantum computation.
It is still possible that, like RSA and ECC, it is discovered that some algorithm exists to speed up reversal of the trapdoor function of these very new cryptographic systems. Once an algorithm is found, it is possible to attack the system having classical computer. In Another way, the algorithm can be used to allow the power of a quantum computer to incapacitate the security of the new cryptographic system significantly.
While quantum safe cryptography may exist, there is a possibility that these systems could be broken once they are implemented. Should a way to break their security that is found, all communications with that scheme would be at risk, including stored past communications. The better and safer choice would be to use a secure scheme such as QKD. QKD derives its security from physicsprinciples and therefore, the only means to crack its security is to break the laws of physics. The particular principle is called the Heisenberg uncertainty principle. The Heisenberg uncertainty principle states that it is not possible to find both the position and momentum of a quantum state exactly. If it is not possible to measure a state perfectly, then it is impossible to copy that state perfectly. Hence, when encoding information in a quantum state, it is impossible to intercept communications without the communicating parties having any information about it. QKD uses Heisenberg uncertainty principle to distribute symmetric encryption keys securely.
Research is being done today to widened the range and increase the data rate of QKD systems, and to add these systems with existing information security solutions. One of the important reasons for the confined range of QKD is because quantum repeaters donâ€™t exist at present. Quantum repeaters should be able to boost the signal to noise ratio of the communication medium to ensure that the signal can transmit upto larger distances, but quantum computation principles are needed to make a quantum repeater. Moreover, the chances of using satellites as part of the QKD infrastructure to expand the range of QKD networks significantly is being investigated. Initial results are hopeful, the point-to-point range of fiber optic lines is 400 km today for research systems while satellite communications can make this intercontinental.
There are largenumbers of companies that offer QKD hardware today; these are ID Quantique, MagiQ Technologies, SeQureNet, and QinetiQ. In addition, Quintessence Labs is in the process of developing a second generation QKD network that depends on continuous variable QKD to increase the secure channel data rate. The systems offered by these companies depends on communication by standard fiber-optic lines and in most of the cases use a different frequency band for quantum communications to make certain simultaneous data and QKD connections on the same line. Thatâ€™s by, QKD works by using existing fiber optic technology.
4. Challenges of QKD
Professional QKD systems were first appearedaround ten years ago. The requirement for secure key distribution has lightened much researchinto the field from private industry. So far, basic systems have been into executionin cities such as Geneva and Dublin. However there aresome restrictions on the practical implementation of QKDthat are yet to be get rid off. Each particle in QKD is important, but transmittingphotons over long distances without obtrusion has been an engineering issue. Fiber-optic cables can transmit photons for around 51 miles, but beyond that over 90% of theparticles become ingest by the cables themselves, which is below the desired meanphoton rate of 0.1. This is more possibly the reason discrete systems to be set up in everycity. Specialized equipment are required for generating and measuring the photons;equipment that is not likely to be found in a personal computer anytime soon.
Due to this, intermediate facilities, euphemistically related to in the industry asâ€œtrusted nodesâ€ must be built to receive the messages. Concern has been impliedly expressedover the chance of a leak or identity forgery within the intermediate step. But theoverall faith within the QKD community seems to be that these problemscan be solved .
There are n numbers of commercial QKD systems present nowadays. These systems allow safe distribution of symmetric keys to secure sensitive data. Prolonged research will extend the ambit of these systems to intercontinental communications and allow safe information transmission worldwide. While attacks on QKD research systems are in knowledge, practical systems use more secure bounds than research systems therefore making a practical attack on QKD applications is very costly. The subsistence of attacks on some QKD systems does show the need for the well-informed use of the systems, however. The safety risks linked with existing public key systems for communication of extremely sensitive information is high today due to the likeliness of challengers storing information for later decoding using a quantum computer. For industries where this threat is unacceptable, QKD systems will possibly give a long-term solution and provide peace of mind. The requirements for maintaining security in quantum world are set to increase speedily. Security information of both quantum and classical systems would be required to make sure the safety of information.
QKD depends on a property of physics to immune the transmission of information. Highly secure communications are feasible by using the QKD channel to transmit symmetric keys. Symmetric keys have much more and proven quantum and attack resilience. Moreover the fact that RSA (Rivest Shamir Adleman) cryptography and ECC cryptography is not possibly secure which makes QKD (quantum key distribution) a safer option even without the availability of quantum computation. There is no ground other than trust in the academic community to suspect that classical public key protocols have not been broken till now and that extremely secretive decoding of Internet traffic is performed right now. QKD systems can provide security based on scientific principles as far as implementation faults are controlled.
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