Abstract Secure communication protocols are becoming increasingly important, e.g. for internet-based communication. Quantum key distribution (QKD) allows two parties, commonly called Alice and Bob, to generate a secret sequence of 0s and 1s called a key that is only known to themselves. Classically, Alice and Bob could never be certain that their communication was not compromised by a malicious eavesdropper. Quantum mechanics however makes secure communication possible. The fundamental principle of quantum mechanics that taking a measurement perturbs the system (unless the measurement is compatible with the quantum state) also applies to an eavesdropper. Using appropriate protocols to create the key, Alice and Bob can detect the presence of an eavesdropper by errors in their measurements. As part of the QuVis Quantum Mechanics Visualisation Project, we have developed a suite of four interactive simulations that demonstrate the basic principles of three different QKD protocols. The simulations use either polarised photons or spin 1/2 particles as physical realisations. The simulations and accompanying activities are freely available for use online or download, and run on a wide range of devices including tablets and PCs. Evaluation with students over three years was used to refine the simulations and activities. Preliminary studies show that the refined simulations and activities help students learn the basic principles of QKD at both the introductory and advanced undergraduate levels.
Abstract Secure communication protocols are becoming increasingly important, e.g. for internet-based communication. Quantum key distribution (QKD) allows two parties, commonly called Alice and Bob, to generate a secret sequence of 0s and 1s called a key that is only known to themselves. Classically, Alice and Bob could never be certain that their communication was not compromised by a malicious eavesdropper. Quantum mechanics however makes secure communication possible. The fundamental principle of quantum mechanics that taking a measurement perturbs the system (unless the measurement is compatible with the quantum state) also applies to an eavesdropper. Using appropriate protocols to create the key, Alice and Bob can detect the presence of an eavesdropper by errors in their measurements. As part of the QuVis Quantum Mechanics Visualisation Project, we have developed a suite of four interactive simulations that demonstrate the basic principles of three different QKD protocols. The simulations use either polarised photons or spin 1/2 particles as physical realisations. The simulations and accompanying activities are freely available for use online or download, and run on a wide range of devices including tablets and PCs. Evaluation with students over three years was used to refine the simulations and activities. Preliminary studies show that the refined simulations and activities help students learn the basic principles of QKD at both the introductory and advanced undergraduate levels.
Quantum Key Distribution (QKD) which is the name of cryptography in quantum environment act as the highest developed area in quantum communication and computing technology (QCIT). \n \nQKD is inventive technology which utilize the laws of quantum to create a cryptographic share key to make the communication system secure. The unique feature of QKD assures eavesdropping detectable during quantum communications which is fascinating for a high-level secure environment.Most of the traditional cryptographic methods which we use currently are based on mathematical scheme or Computational complexity theory which are not completely safe. Using quantum cryptography has been achieved extensive steps in communication security establishment. As the information Unit has been changed from “bit” to Quantum bit (Qubit), a new element has been offered that can guarantee the shared information confidentiality between parties. The confidentiality of system is established via exchanging a secret key through a channel of quantum, the key which we use for encrypting the shared data. This structure has quantum integration which has been developed by physics law and techniques of cryptography. \n \nThis thesis has proposed a modified version of QKD protocol, this new protocol will generate a cryptographic share key for a more efficient, lower cost and secure communication between two parties (sender and Receiver). This new protocol principal is similar to BBM92, but the source of photon moved to sender instead of third-party photon generator, following steps will be executed in this Experiment: \n \n•\tObserve different categories protocols of QKD in details \n•\tThe Quantum Mechanics Visualisation Project (QuVis) is the simulation software that has been used for implementing the proposed protocol [BB84 with spin] among the other three (BBM92, B92 and BB84). \n•\tProbability ratio of error will be tested and compared for all protocols, for this experiment 100 to 5000 photons will be sent. \n \nBy Analysing collected data in this experiment, it will be determined which one of this four protocols lead the detecting of eavesdropping. Simulation software accomplishes the value of error key probability which receiver can use and should not pass over the range limit of 0.25 & 0.5.
Quantum key distribution (QKD) is intended to produce cryptographic secret keys between two remote parties, usually called Alice and Bob. Even though QKD has been proven to be unconditionally secure against the eavesdropper, commonly called Eve, practical implementations of QKD may contain vulnerabilities that may lead to the generated secret keys being compromised. In order to detect the presence of the eavesdropper in the channel, in our proposal Alice introduces an interleaved sequence of decoy states which produce a characteristic distribution at Bob's station. Thus, in analyzing such distribution in presence and absence of the eavesdropper Eve, her activity in the channel is detected. This protocol doesn’t require changes at the quantum physical level, but it can be incorporated at the high software level.
The security of information in Internet-based communication is essential. The existence of tappers to make information can be known by unauthorized parties, and it will give a fake information from the previous one. As technology develops, secure communication protocols become an important part. Quantum Key Distribution is a nowadays technology as a part of security improvement to overcome key distribution issues in against attackers. Quantum Key Distribution (QKD) uses a quantum property in exchanging information called photons, as carriers of information in security systems. QKD is inseparable from protocols BB84 and B92, therefore the purposes of this paper are to test QuVis based on future work of previous research, analyze the probability error comparison of BB84 protocol, B92 protocol and simulator software review. The results of this research show that B92 protocol gives more advantage in detecting eavesdropping in lower rates than BB84 protocol and the software simulation is succeed by showing the value of probability key that can be used by Bob which does not cross the limit (0.5 and 0.25).
Quantum Key Distribution (QKD) employs the laws of quantum mechanics for the purpose of cryptography. Two parties, commonly called Alice and Bob, are able to share a random key which is used to encrypt a message. Any eavesdropper trying to intercept their key will have to make measurements, thereby disturbing the system. This can be detected by Alice and Bob and they will then discard their key. Polarisation encoded QKD protocols use the polarisation of single photons as qubits to generate a cryptographic key. This can be implemented using a fibre optic link between Alice and Bob but the polarisation of light is altered when passed through a fibre due to birefringence caused by asymmetries in the fibre. This causes refractive differences for orthogonal components of the state of polarisation of light, so the polarisation is rotated as the photon is transmitted through the fibre. If the fibre is fixed, the change of polarisation will be unique and constant. This can be compensated by rotating each photon appropriately to its original state. Under typical environmental conditions, such as temperature changes and vibrations, the birefringence effects vary and should be compensated in real time. Therefore, an active polarisation controller is needed in order to maintain the state of polarisation of each qubit. An investigation was done to first track how the state of polarisation changes over time in a natural environment. Both wavelength-division multiplexing and time-division multiplexing were investigated as testing methods for the compensation system. A timedivision multiplexed system was developed to compensate the changes in polarisation. Since QKD protocols such as BB84 and B92 utilise two non-orthogonal bases, two polarisation controllers are usually used for compensation. However, by using a search algorithm, one polarisation controller was able to isolate the plane on the Poincare sphere that passes through both bases, thus compensating non-orthogonal states with one device.
As the digital front becomes our new frontier, and digital data becomes increasingly vulnerable to highly sophisticated cyber attacks, conventional encryption approaches may no longer be sufficient to withstand a quantum attack. The focus of this work is to deploy a simulation of the BB84 protocol, one of the first Quantum Key Distribution (QKD) protocols developed by Charles Bennett and Gilles Brassard in 1984. The simulation involves two communicating parties, Alice and Bob, with Bob creating a secret keys generated cryptographically and sending it reliably over to Alice using quantum bits, or qubits. By leveraging quantum mechanics, this protocol ensures that any interception can be identified, thus bolstering both the integrity and confidentiality of the key exchange through scientists' understanding of superposition and the no-cloning principle. In the simulation, the potential of quantum communication to achieve secure key distribution over an insecure channel is demonstrated. Differently from traditional encryption protocols, QKD guarantees security not on computational but on physical basis. The aim of this paper is to show the feasibility and robustness of the BB84 protocol for actual cryptographic applications. This models the protocol between Alice and Bob, which paves the way for quantum-proof encryption systems and is a relevant step towards next generation cyber security.
Employing the fundamental laws of quantum physics, Quantum Key Distribution (QKD) promises the unconditionally secure distribution of cryptographic keys. However, in practical realisations, a QKD protocol is only secure, when the quantum bit error rate introduced by an eavesdropper unavoidably exceeds the system error rate. This condition guarantees that an eavesdropper cannot disguise his presence by simply replacing the original transmission line with a less faulty one. Unfortunately, this condition also limits the possible distance between the communicating parties, Alice and Bob, to a few hundred kilometers. To overcome this problem, we design a QKD protocol which allows Alice and Bob to distinguish system errors from eavesdropping errors. If they are able to identify the origin of their errors, they can detect eavesdropping even when the system error rate exceeds the eavesdropping error rate. To achieve this, the proposed protocol employs an alternative encoding of information in two-dimensional photon states. Errors manifest themselves as quantum bit and as index transmission errors with a distinct correlation between them in case of intercept-resend eavesdropping. As a result, Alice and Bob can tolerate lower eavesdropping and higher system error rates without compromising their privacy.