Abstract Quantum digital signature (QDS) provides information-theoretic security and enables fundamental cryptographic functionalities, including integrity, non-repudiation, and data origin authentication. Existing QDS implementations, however, assign fixed user roles - signer, authenticator, and verifier - which limits their applicability in practical quantum networks, where role flexibility is essential. In this work, we implement a QDS protocol on a three-user fiber-optic quantum network in which any participant can dynamically assume the role of signer. Every node uses an identical design for encoding and decoding time-bin quantum states, enabling flexible signer assignment without hardware reconfiguration. We evaluate the signature rate and secret key rate for all possible signer configurations and show that valid signatures can be generated even in regimes where quantum key distribution (QKD) fails to produce a secret key. This result highlights a fundamental practical advantage of QDS over QKD at small classical post-processing block sizes, where key distillation is not achievable. Our results establish the feasibility of reconfigurable quantum signature networks and represent an important step toward scalable and robust quantum communication infrastructures.
Abstract Quantum digital signature (QDS) provides information-theoretic security and enables fundamental cryptographic functionalities, including integrity, non-repudiation, and data origin authentication. Existing QDS implementations, however, assign fixed user roles - signer, authenticator, and verifier - which limits their applicability in practical quantum networks, where role flexibility is essential. In this work, we implement a QDS protocol on a three-user fiber-optic quantum network in which any participant can dynamically assume the role of signer. Every node uses an identical design for encoding and decoding time-bin quantum states, enabling flexible signer assignment without hardware reconfiguration. We evaluate the signature rate and secret key rate for all possible signer configurations and show that valid signatures can be generated even in regimes where quantum key distribution (QKD) fails to produce a secret key. This result highlights a fundamental practical advantage of QDS over QKD at small classical post-processing block sizes, where key distillation is not achievable. Our results establish the feasibility of reconfigurable quantum signature networks and represent an important step toward scalable and robust quantum communication infrastructures.
We propose an entanglement-based quantum digital signature (QDS) protocol optimized for quantum networks. The protocol follows the Lamport-inspired QDS paradigm but eliminates QKD post-processing by signing and verifying with raw conclusive keys, thereby reducing latency and implementation complexity. We provide a finite-size security analysis of robustness, unforgeability, and non-repudiation. Under standard fiber-loss and detector models, simulations show a consistent signature rate advantage over a representative Lamport-inspired QDS baseline across metro-to-regional distances. The proposed protocol is practical for near-term deployment while preserving end-to-end, finite key security guarantees.
The development of quantum networks is paramount towards practical and secure communications. Quantum digital signatures (QDS) offer an information-theoretically secure solution for ensuring data integrity, authenticity, and non-repudiation, rapidly growing from proof-of-concept to robust demonstrations. However, previous QDS systems relied on expensive and bulky optical equipment, limiting large-scale deployment and reconfigurable networking construction. Here, we introduce and verify a chip-based QDS network, placing the complicated and expensive measurement devices in the central relay while each user needs only a low-cost transmitter. We demonstrate the network with a three-node setup using an integrated encoder chip and decoder chip. By developing a 1-decoy-state one-time universal hash-QDS protocol, we achieve a maximum signature rate of 0.0414 times per second for a 1 Mbit file over fiber distances up to 200 km, surpassing all current state-of-the-art QDS experiments. This study validates the feasibility of chip-based QDS, paving the way for large-scale deployment and integration with existing fiber infrastructure.
The development of quantum networks is paramount towards practical and secure communications. Quantum digital signatures (QDS) offer an information-theoretically secure solution for ensuring data integrity, authenticity, and non-repudiation, rapidly growing from proof-of-concept to robust demonstrations. However, previous QDS systems relied on expensive and bulky optical equipment, limiting large-scale deployment and reconfigurable networking construction. Here, we introduce and verify a chip-based QDS network, placing the complicated and expensive measurement devices in the central relay while each user needs only a low-cost transmitter. We demonstrate the network with a three-node setup using an integrated encoder chip and decoder chip. By developing a 1-decoy-state one-time universal hashing-QDS protocol, we achieve a maximum signature rate of 0.0414 times per second for a 1 Mbit messages over fiber distances up to 200 km, surpassing all current state-of-the-art QDS experiments. This study validates the feasibility of chip-based QDS, paving the way for large-scale deployment and integration with existing fiber infrastructure.
The development of quantum networks will be paramount towards practical and secure telecommunications. These networks will need to sign and distribute information between many parties with information-theoretic security, requiring both quantum digital signatures (QDS) and quantum key distribution (QKD). Here, we introduce and experimentally realise a quantum network architecture, where the nodes are fully connected using a minimum amount of physical links. The central node of the network can act either as a totally untrusted relay, connecting the end users via the recently introduced measurement-device-independent (MDI)-QKD, or as a trusted recipient directly communicating with the end users via QKD. Using this network, we perform a proof-of-principle demonstration of QDS mediated by MDI-QKD. For that, we devised an efficient protocol to distil multiple signatures from the same block of data, thus reducing the statistical fluctuations in the sample and greatly enhancing the final QDS rate in the finite-size scenario.
Digital signature (DS) is an essential application of cryptography, used to certify the provenance of a message and its authenticity, guaranteeing the non-repudiation, unforgeability, and transferability of messages. However, the forthcoming advent of quantum computation poses a significant threat to classical signature schemes. A possible solution could be the introduction of novel DS schemes based on the fundamental laws of quantum physics. Recently, several quantum DS (QDS) protocols have been proposed, even relying on the exploitation of off-the-shelf quantum key distribution (QKD) solutions. However, their efficiency and large signature size, uncorrelated to the size of the message to sign, represent the main limitation in their employment in a practical scenario. A trade-off solution could be a quantum-assisted DS (QADS), where the QKD technology is exploited together with classical cryptographic functions to achieve a stronger DS scheme, more resistant even to quantum attacks. We propose a generalized quantum-assisted digital signature (G-QADS) protocol based on a hybrid system, composed by the standard Wegman-Carter Message Authentication Code (WG-MAC) together with symmetric QKD keys, to enhance the security of the DS, allowing messages with arbitrary lengths to be signed while maintaining a suitable DS length. In this work, the G-QADS process is proposed for a three-party configuration (one signer and two verifiers), where the third participant is involved in the procedure just in the case of contention between the other two parties. The G-QADS protocol is then experimentally tested to prove its resilience to forging and non-repudiation attacks, demonstrating its capability in securing the message signature (with a success probability of the attacks <10 −18 ). The performance is experimentally tested exploiting QKD prototypes based on standard BB84 protocol with decoy states and polarization encoding, in a software-defined network (SDN) infrastructure supervised by a single SDN controller, which provides the management of both classical and quantum communication channels. The proposed solution could push the practical exploitation of QKD into a new application domain, leading to a more pervasive integration of quantum technology in realistic scenarios.
Quantum digital signatures (QDS) offer information-theoretic security for message integrity, authenticity, and non-repudiation, and constitute a fundamental cryptographic primitive for future quantum networks. Despite significant progress, the practical deployment of QDS has been severely constrained by limited signature rates and poor tolerance to channel loss, particularly in long-distance and metropolitan-scale networks. Here, we report a high-rate, loss-resilient QDS system that overcomes these two key bottlenecks simultaneously. Our implementation combines intrinsically phase-stable polarization modulation based on a Sagnac interferometer with gigahertz-rate quantum state encoding and low-timing-jitter superconducting nanowire single-photon detectors, enabling robust and continuous operation at high repetition frequencies. By integrating this hardware platform with a one-time universal hashing-based QDS protocol, we achieve a signature rate improvement of more than two orders of magnitude compared with existing QDS implementations under comparable channel-loss conditions. Notably, the system maintains a non-zero effective signature rate of approximately 1.25 times per second at a total channel loss of up to 49.05 dB, representing the highest loss tolerance reported for QDS to date. These results establish a practical and scalable technological pathway for deploying QDS in real-world quantum communication networks.