As quantum communication evolves from point-to-point to multi-user networks, existing scalable schemes for multi-party quantum key distribution increasingly reveal their limitations in complex scenarios. These limitations are primarily manifested as a reliance on a central node, which results in insufficient hierarchical control capabilities of the system. Furthermore, existing schemes cannot enforce communication controllability at the quantum physical layer, making authorized communication difficult. To address these challenges, we propose a GHZ-state-based quantum-layer authorized hierarchical multi-user quantum key distribution scheme. By exploiting the global correlation of multipartite entanglement, authorization is mapped onto constraints imposed by managers’ measurement outcomes on receivers’ correlation structures, enabling hierarchically controlled key establishment. Specifically, any two users dynamically act as managers, whose measurements act as entanglement constraints dictating whether remaining users successfully establish a shared secret key. Theoretical analysis demonstrates the scheme guarantees correctness and consistency of key generation. Simulation results further indicate good robustness against typical types of channel noise, enabling stable controlled quantum key distribution within low-noise regimes. This work shifts communication authorization from classical mechanisms at the application layer to the quantum physical layer, providing a promising approach for secure quantum communication in complex networks.
As quantum communication evolves from point-to-point to multi-user networks, existing scalable schemes for multi-party quantum key distribution increasingly reveal their limitations in complex scenarios. These limitations are primarily manifested as a reliance on a central node, which results in insufficient hierarchical control capabilities of the system. Furthermore, existing schemes cannot enforce communication controllability at the quantum physical layer, making authorized communication difficult. To address these challenges, we propose a GHZ-state-based quantum-layer authorized hierarchical multi-user quantum key distribution scheme. By exploiting the global correlation of multipartite entanglement, authorization is mapped onto constraints imposed by managers’ measurement outcomes on receivers’ correlation structures, enabling hierarchically controlled key establishment. Specifically, any two users dynamically act as managers, whose measurements act as entanglement constraints dictating whether remaining users successfully establish a shared secret key. Theoretical analysis demonstrates the scheme guarantees correctness and consistency of key generation. Simulation results further indicate good robustness against typical types of channel noise, enabling stable controlled quantum key distribution within low-noise regimes. This work shifts communication authorization from classical mechanisms at the application layer to the quantum physical layer, providing a promising approach for secure quantum communication in complex networks.
Abstract Multi-party quantum key agreement (MQKA) enables a group of mutually untrusted users to jointly establish a secret key with equal influence, a capability not provided by two-party quantum key distribution (QKD) and increasingly relevant for securing resilient infrastructure such as quantum-enabled smart grid networks and distributed cyber-physical systems. We present a high-dimensional Greenberger-Horne-Zeilinger (GHZ)-based MQKA that simultaneously targets rigorous security, provable fairness, and practical loss tolerance. The protocol distributes an N -partite d -level GHZ state in a star (with an optional star-of-stars hierarchy for large N ) and maps each user’s contribution to local XdaZdb X d a Z d b operations. A commit-then-reveal layer makes inputs binding and hiding, yielding equal influence fairness over Zd Z d with a strict fair-abort guarantee. Composable secrecy is established via entropy bounds and a Devetak-Winter-style key rate analysis, strengthened by test-round statistics; we connect Mermin/Svetlichny-type correlators to min-entropy lower bounds and incorporate full leakage accounting and finite-key penalties. We model depolarizing, shift/phase (Weyl), amplitude-damping, erasures, detector efficiency, and dark counts, and derive closed-form mappings from device parameters to symbol/phase errors. Monte Carlo studies confirm that d>2 d > 2 expands the positive-rate region and reduces the global survival required for a given throughput compared with qubit GHZ MQKA under identical conditions. We discuss potential photonic realizations (time-bin or frequency-bin encoding, discrete Fourier transform networks, and superconducting nanowire detectors) and architectural pathways toward larger N via hierarchical clustering, while acknowledging the significant technological challenges that would need to be overcome to realize high-dimensional multipartite entanglement experimentally. Overall, the scheme delivers higher efficiency per entangled state, rigorous fairness, and composable security with realistic noise and loss, addressing key gaps in current MQKA designs for resilient infrastructure.
The quantum secret sharing scheme can be implemented within realistic,highly secure multi-user communication network,using Greenberger Horne Zeilinger(GHZ) states.The quantum communication network marries a variety of GHZ states to well establish the secure key distribution system employed in conjunction with the nodes and control centers.Compared with the classical quantum cryptography,it is theoretically proved that an eavesdropper Eve invariably introduces errors within communication network if she wants to gain useful information.The nodes and control centers must find Eve to guarantee the security of the network.
Quantum Cryptography (QC) is the emerging field of the current world and the potential player of the future. Quantum Key Distribution (QKD) is the matured discipline of QC and available in the market to establish a secret key between parties. In order to achieve in multiparty, basically quantum entanglement has been applied over a theoretical settings. However, due to practical limitation, entanglement based research has a feasible difficulty with current technology. The thesis principal goal is to propose a framework for quantum protocol layer for secure key management without entanglement over multiparty environment. In the secret key management, conference key or Multiparty QKD (MQKD) and joint-venture key or Public Shared Secret Quantum Key (PSSQK) protocols acted as a top layer and quantum user authentication scheme as a middle layer and the standard QKD operation as a bottom layer. The proposed secrete key management protocols are based on secret key between parties using QKD, modified error correction code and linear independent matrix. These protocols require only classical communication and yield higher secret key rate regardless of distance and noise. The security analysis using guessing entropy has applied and results shows only negligible amount information can be extracted during eavesdropping. The challenge-challenge response technique has been applied to proposed quantum user authentication scheme for verification of quantum user. This is a bidirectional authentication scheme and requires both quantum and classical channel to execute and has two modes of operation, i.e., initial and session authentication.Due to deterministic key distribution orientation, the efficiency of protocol reaches up to 100% in terms of reduction of photon wastage during communication. Further, this scheme is resilient to various quantum security attacks However, this scheme requires noiseless quantum channel in order to detect the insider and outsider attacks during authentication. A GUI based discrete event simulation has developed using OptiSystem™ in order to test the practical feasibility of proposed quantum cryptography protocol layer. The polarized based discrete variable QKD protocols have been designed and analyzed. Due to lack of real receiver setup, the results have showed lower quantum bit error rate. Further, we analyzed the impact of polarization structure of qubit due to noise, loss and distance over fiber optics and free space. A multiparty QKD setuphas been designed based on frequency division multiplexing (FDM) centralized quantum channel server. This approach reduces the requirement of total quantum channel from N*(N-1)/2 to N and each party requires one quantum channel to communicate with all other parties. The bit commitment protocol and message authentication in the layer has considered for the future research direction.
According to the shortcoming of the classical quantum cryptography with ERP states,how this quantum-secret-sharing scheme is implemented within realistic,highly secure multi-user communication network is presented,using greenberger-horne-zeilinger(GHZ) states.The quantum communication network marries a variety of GHZ states to well established internet technology in order to build a secure key distribution system employed in conjunction with the nodes and control centers.In communication network,eavesdropper Eve transmit with three party,useful information is gain,the errors is introduced.The nodes and control centers can find Eve,the security of multi-user quantum network is ensured.
A quantum key distribution network enables pairs of users to generate independent secret keys by leveraging the principles of quantum physics. For end-to-end secure communication, a user pair's secret key must remain secure against any third parties, including both external eavesdroppers and other network users. However, isolating a given user pair from the remaining users while maintaining a high key rate is challenging when all users are intrinsically correlated, particularly in continuous-variable networks. This results in either a low key rate or incomplete end-to-end security. Here, we introduce a multiuser security framework, offering a general and comprehensive end-to-end key rate formula, against the worst-case scenario where an eavesdropper fully exploits the user crosstalk. Building on this framework, we propose a multiuser protocol that achieves the theoretical upper limit in all practical deployments within a 100 km range. Applied to a three-node network, it achieves an Mbps-level per-user key rate and an overall network key rate reaching 90% of the upper limit. The proposed solution supports scalable implementations using telecom-compatible components, while the method for obtaining the accessible information in the network is broadly applicable and can be extended to various multipartite quantum information systems.
Quantum key distribution (QKD) is a cornerstone of secure communication in the quantum era, yet most existing protocols are designed for point-to-point transmission, limiting their scalability in networked environments. In this work, we introduce Loop-Back QKD, a novel QKD protocol that supports both two-party linear configurations and scalable multiuser ring topologies. By leveraging a structured turn-based mechanism and bidirectional pulse propagation, the protocol enables efficient key distribution while reducing the quantum bit error rate (QBER) through a multi-pulse approach. Unlike trusted-node QKD networks, Loop-Back QKD eliminates intermediate-node vulnerabilities, as secret keys are never processed by intermediate nodes. Furthermore, unlike Measurement-Device-Independent (MDI-QKD) and Twin-Field QKD (TF-QKD), which require complex entanglement-based setups, Loop-Back QKD relies solely on direct polarization transformations, reducing vulnerability to side-channel attacks and practical implementation challenges. Additionally, our analysis indicates that multi-pulse Loop-Back QKD can tolerate higher QBER thresholds. However, this increased robustness comes at the cost of a lower key rate efficiency compared to standard QKD schemes. This design choice enhances its robustness against real-world adversarial threats, making it a strong candidate for secure multiuser communication in local and metropolitan-scale quantum networks.