Multi-user Quantum Key Distribution Research Articles

Mediated semi-quantum key distribution with improved efficiency

Mediated semi-quantum key distribution involves the use of two end-users who have very restricted, almost classical, capabilities, who wish to establish a shared secret key using the help of a fully-quantum server who may be adversarial. In this paper, we introduce a new mediated semi-quantum key distribution protocol, extending prior work, which has asymptotically perfect efficiency. Though this comes at the cost of decreased noise tolerance, our protocol is backwards compatible with prior work, so users may easily switch to the old (normally less efficient) protocol if the noise level is high enough to justify it. To prove security, we show an interesting reduction from the mediated semi-quantum scenario to a fully-quantum entanglement based protocol which may be useful when proving the security of other multi-user quantum key distribution protocols.

Phase modulation polarization encoding module applied to one-to-many QKD network based on wavelength division multiplexing

The quantum key distribution (QKD) network is a promising solution for secure communications. In this paper, we proposed a polarization-independent phase-modulated polarization encoding module, and it can be combined with a dense wavelength division multiplexer (DWDM) to achieve multi-user QKD. We experimentally test the encoding module with a repetition rate of 62.5 MHz, and its average quantum bit error rate (QBER) is as low as 0.4%. Finally, we implement a principle verification test for simultaneous QKD for 1 to 2 users in 100 min, and the average QBER of two users under the transmission distance of 1 km and 5 km is kept below 0.8%. Due to the use of polarization encoding, the module can also realize scalable network architecture in free-space QKD systems in the future.

Development of authentication code for multi-access optical code division multiplexing based quantum key distribution

One-weight authentication code for multi-user quantum key distribution (QKD) is proposed. The code is developed for Optical Code Division Multiplexing (OCDMA) based QKD network. A unique address assigned to individual user, coupled with degrading probability of predicting the source of the qubit transmitted in the channel offer excellent secure mechanism against any form of channel attack on OCDMA based QKD network. Flexibility in design as well as ease of modifying the number of users are equally exceptional quality presented by the code in contrast to Optical Orthogonal Code (OOC) earlier implemented for the same purpose. The code was successfully applied to eight simultaneous users at effective key rate of 32 bps over 27 km transmission distance.

Multi-user quantum key distribution with entangled photons from an AlGaAs chip

In view of real-world applications of quantum information technologies, the combination of miniature quantum resources with existing fibre networks is a crucial issue. Among such resources, on-chip entangled photon sources play a central role for applications spanning quantum communications, computing and metrology. Here, we use a semiconductor source of entangled photons operating at room temperature in conjunction with standard telecom components to demonstrate multi-user quantum key distribution, a core protocol for securing communications in quantum networks. The source consists of an AlGaAs chip-emitting polarisation entangled photon pairs over a large bandwidth in the main telecom band around 1550 nm without the use of any off-chip compensation or interferometric scheme; the photon pairs are directly launched into a dense wavelength division multiplexer (DWDM) and secret keys are distributed between several pairs of users communicating through different channels. We achieve a visibility measured after the DWDM of 87% and show long-distance key distribution using a 50-km standard telecom fibre link between two network users. These results illustrate a promising route to practical, resource-efficient implementations adapted to quantum network infrastructures.

Authenticated multi-user quantum key distribution with single particles

Quantum key distribution (QKD) has been growing rapidly in recent years and becomes one of the hottest issues in quantum information science. During the implementation of QKD on a network, identity authentication has been one main problem. In this paper, an efficient authenticated multi-user quantum key distribution (MQKD) protocol with single particles is proposed. In this protocol, any two users on a quantum network can perform mutual authentication and share a secure session key with the assistance of a semi-honest center. Meanwhile, the particles, which are used as quantum information carriers, are not required to be stored, therefore the proposed protocol is feasible with current technology. Finally, security analysis shows that this protocol is secure in theory.

Quantum secured gigabit optical access networks.

Optical access networks connect multiple endpoints to a common network node via shared fibre infrastructure. They will play a vital role to scale up the number of users in quantum key distribution (QKD) networks. However, the presence of power splitters in the commonly used passive network architecture makes successful transmission of weak quantum signals challenging. This is especially true if QKD and data signals are multiplexed in the passive network. The splitter introduces an imbalance between quantum signal and Raman noise, which can prevent the recovery of the quantum signal completely. Here we introduce a method to overcome this limitation and demonstrate coexistence of multi-user QKD and full power data traffic from a gigabit passive optical network (GPON) for the first time. The dual feeder implementation is compatible with standard GPON architectures and can support up to 128 users, highlighting that quantum protected GPON networks could be commonplace in the future.

Multi-user quantum key distribution with collective eavesdropping detection over collective-noise channels**Project supported by the National Natural Science Foundation of China (Grant Nos. 61272057, 61170270, and 61309029), Beijing Higher Education Young Elite Teacher Project, China (Grant Nos. YETP0475 and YETP0477), and BUPT Excellent Ph.D. Students Foundation, China (Grant No. CX201441).

A multi-user quantum key distribution protocol is proposed with single particles and the collective eavesdropping detection strategy on a star network. By utilizing this protocol, any two users of the network can accomplish quantum key distribution with the help of a serving center. Due to the utilization of the collective eavesdropping detection strategy, the users of the protocol just need to have the ability of performing certain unitary operations. Furthermore, we present three fault-tolerant versions of the proposed protocol, which can combat with the errors over different collective-noise channels. The security of all the proposed protocols is guaranteed by the theorems on quantum operation discrimination.

具有双向认证功能的多方量子密钥分发

Based on the entanglement feature of Greenberger-Horne-Zeilinger states, a multi-user quantum key distribution with mutual authentication is proposed. In the protocol, a semi-trusted third party, who may misbehave on its own but will conspire with none of the participants, is introduced to help arbitrary two users on a quantum network to achieve this secure task. Firstly, the third party prepares a three-particle entangled state. Then, he keeps one particle in his hand, and sends two particles to these two users respectively. Meanwhile, a keyed one-way hash function is utilized to generate an authentication message, in terms of which three parties respectively make an appropriate single-particle measurement on the particles in their hands. According to the measurement results, the third party can verify the identity of one user. It implies that one user is able to authenticate the other user with the assistance of the third party. After that, two participants use the remainder measurement results to generate a common session key. Moreover, the practical implementation of the presented protocol is discussed, which illustrates that this protocol is feasible under the current techniques. In the end, the security of the presented protocol is analyzed. It is shown that this protocol is secure in theory by proving that the presented protocol can stand against several common attacks.

A quantum access network

The theoretically proven security of quantum key distribution (QKD) could revolutionize the way in which information exchange is protected in the future. Several field tests of QKD have proven it to be a reliable technology for cryptographic key exchange and have demonstrated nodal networks of point-to-point links. However, until now no convincing answer has been given to the question of how to extend the scope of QKD beyond niche applications in dedicated high security networks. Here we introduce and experimentally demonstrate the concept of a 'quantum access network': based on simple and cost-effective telecommunication technologies, the scheme can greatly expand the number of users in quantum networks and therefore vastly broaden their appeal. We show that a high-speed single-photon detector positioned at a network node can be shared between up to 64 users for exchanging secret keys with the node, thereby significantly reducing the hardware requirements for each user added to the network. This point-to-multipoint architecture removes one of the main obstacles restricting the widespread application of QKD. It presents a viable method for realizing multi-user QKD networks with efficient use of resources, and brings QKD closer to becoming a widespread technology.

Multi-user quantum key distribution based on Bell states with mutual authentication

A new multi-user quantum key distribution protocol with mutual authentication is proposed on a star network. Here, two arbitrary users are able to perform key distribution with the assistance of a semi-trusted center. Bell states are used as information carriers and transmitted in a quantum channel between the center and one user. A keyed hash function is utilized to ensure the identities of three parties. Finally, the security of this protocol with respect to various kinds of attacks is discussed.

Multiple-Access Quantum Key Distribution Networks

This paper addresses multi-user quantum key distribution networks, in which any two users can mutually exchange a secret key without trusting any other nodes. The same network also supports conventional classical communications by assigning two different wavelength bands to quantum and classical signals. Time and code division multiple access (CDMA) techniques, within a passive star network, are considered. In the case of CDMA, it turns out that the optimal performance is achieved at a unity code weight. A listen-before-send protocol is then proposed to improve secret key generation rates in this case. Finally, a hybrid setup with wavelength routers and passive optical networks, which can support a large number of users, is considered and analyzed.

Coincidence Rates for Photon Pairs in WDM Environment

We demonstrate the flexibility that a wavelength selective switch could offer to bandwidth provisioning of potential multi-user quantum key distribution networks based on entangled pair sources. We derive an analytical expression relating the coincidence detection rates of the photon pairs to the switch bandwidth characteristics. Experimentally measured coincidence rates verify the theory in three distinct network configurations.

Comment on “ N quantum channel are sufficient for multi-user quantum key distribution protocol between n users”

This study points out that a malicious gateway in Hong et al.'s multi-user quantum key distribution protocol [Optics Communication 283 (2010) 2644] may be able to reveal the secret key of the protocol without being detected. An improvement is suggested to avoid the weakness.

Cryptanalysis and improvement of a multi-user quantum key distribution protocol

A multi-user quantum key distribution protocol [C.H. Hong et al., Opt. Commun. 283 (2010) 2644] was proposed, in which any two among n users of the system can communicate with each other, even though there is no direct quantum channel between them. Nevertheless, we show that the mediator Trent, who performs entanglement swapping in this protocol, has a way to eavesdrop on the communication between the two users without being detected. We also give an effective method to solve the security leak.

Formula omitted] quantum channels are sufficient for Multi-user Quantum Key Distribution protocol between [formula omitted] users

Quantum Key Distribution (QKD) protocols enable two parties to communicate in a secret manner. As it is necessary that there be a quantum channel between two users, n ( n - 1 ) / 2 quantum channels are required for a QKD system of n users. We here propose a Multi-user Quantum Key Distribution protocol that utilizes entanglement swapping and by which only n quantum channels are needed for a communication system of n users. Any two among n users of the system can communicate with each other, even though there is no direct quantum channel between them. This is possible because entanglement swapping entangles the quantum states of the two users, establishing a quantum connection between them. Hence n quantum channels are sufficient for communication between n users. Furthermore, Trent, who performs entanglement swapping, has no way to fraudulently intervene in or eavesdrop on the communication between two users.

Comparison of 4 Multi-User Passive Network Topologies for 3 Different Quantum Key Distribution

The purpose of this paper is to compare the performance of four passive optical network topologies in implementing multi-user quantum key distribution, using 3 protocols proposed by quantum cryptography (B92, EPR, and SSP). The considered networks are the passive-star network, the optical-ring network based on the Signac interferometer, the wavelength-routed network, and the wavelength-addressed bus network. The quantum bit-error rate and sifted key rate for each of these topologies are analysed to determine their suitability for providing quantum key distribution-service to networks of various sizes. The efficiency of the three considered protocols is also determined.

Expandable quantum key distribution networks based on secret bits comparison

A scheme of quantum network based on multiuser differential phase shift quantum key distribution system (DPS–QKD) is proposed. In this quantum network, arbitrary two users can achieve secret bits sharing by point-to-multipoint quantum key distribution and secret bits comparison. A protocol of secret bits sharing between arbitrary two users is presented. This network can implement secret bits distribution over 200 km with higher key generation rate by today's technologies. In theory, the capacity of user numbers in this network is unlimited. Hence, our proposed quantum network can serve for a metropolitan QKD network. A wide area QKD network can be constructed with this metropolitan QKD network.

Multiuser quantum key distribution over telecom fiber networks

We report five-user quantum key distribution (QKD) over switched fiber networks in both star and tree configurations, using the BB84-protocol [1] with phase encoding. Both setups implement polarization insensitive phase modulators, necessary for birefringent single mode fiber (SMF) networks. In both configurations we have achieved transmission distances between 25 km and 50 km with quantum bit error rates between 1.24% and 5.56% for the mean photon number μ = 0.1 . The measurements have showed feasibility of multiuser QKD over switched fiber networks, using standard fiber telecom components.

Quantum Key Distribution Network Based on Differential PhaseShift

Using a series of quantum correlated photon pairs, we propose atheoretical scheme for any-to-any multi-user quantum keydistribution network based on differential phase shift. Thedifferential phase shift and the different detection time slotsensure the security of our scheme against eavesdropping. We discussthe security under the intercept–resend attack and the sourcereplacement attack.

Experimental multiuser quantum key distribution network using a wavelength-addressed bus architecture

A six-user quantum key distribution network implemented on a bus topology is experimentally demonstrated. The network employs the BB84 protocol to transmit cryptographic keys encoded unto the phase states of highly attenuated laser light to distances of up to 31 km in a standard telecommunication-grade fiber. Each user on the network is assigned a unique wavelength for communication with the network server at a time. The measured quantum bit error rate and sifted key rate compare favorably with theoretical results