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Entropy

Quantum Digital Signature Using Entangled States for Network

Changho Hong, Youn-Chang Jeong, Osung Kwon, Se-Wan Ji

Published Nov 20, 2025• 0 citations
Publisher

Abstract

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.

DOI
10.3390/e27111179

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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.
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.
Quantum digital signatures (QDS) exploit quantum laws to guarantee non-repudiation, unforgeability and transferability of messages with information-theoretic security. Current QDS protocols face two major restrictions, including the requirement of the symmetrization step with additional secure classical channels and the quadratic scaling of the signature rate with the probability of detection events. Here, we present an efficient QDS protocol to overcome these issues by utilizing the classical post-processing operation called post-matching method. Our protocol does not need the symmetrization step, and the signature rate scales linearly with the probability of detection events. Simulation results show that the signature rate is three orders of magnitude higher than the original protocol in a 100-km-long fiber. This protocol is compatible with existing quantum communication infrastructure, therefore we anticipate that it will play a significant role in providing digital signatures with unconditional security.
The quantum digital signature protocol offers a replacement for most aspects of public-key digital signatures ubiquitous in today's digital world. A major advantage of a quantum-digital-signatures protocol is that it can have information-theoretic security, whereas public-key cryptography cannot. Here we demonstrate and characterize hardware to implement entanglement-based quantum digital signatures over our campus network. Over 25 hours, we collect measurements on our campus network, where we measure sufficiently low quantum bit error rates (<5% in most cases) which in principle enable quantum digital signatures at over 50 km as shown through rigorous simulation accompanied by a noise model developed specifically for our implementation. These results show quantum digital signatures can be successfully employed over deployed fiber. Moreover, our reported method provides great flexibility in the number of users, but with reduced entanglement rate per user. Finally, while the current implementation of our entanglement-based approach has a low signature rate, feasible upgrades would significantly increase the signature rate.
Abstract Quantum digital signature (QDS) ensures the authenticity, integrity, and non-repudiation of message transmission with information-theoretic security. However, most existing QDS protocols require users to maintain aligned reference frames, which is a complex and time-consuming process, especially in large-scale networks. To overcome this limitation, we propose a reference-frame-independent (RFI)-QDS protocol that eliminates the need for reference frame alignment by utilizing an RFI quantum key distribution technique. Our RFI-QDS protocol enhances signature rates and robustness by bypassing the reference calibration step. This advantage becomes particularly significant under conditions of large reference misalignment. Simulation results demonstrate that our protocol achieves significantly higher signature rates compared to traditional QDS schemes, even in the presence of severe reference misalignment.
The quantum digital signature protocol offers a replacement for most aspects of public-key digital signatures ubiquitous in today's digital world. A major advantage of a quantum-digital-signatures protocol is that it can have information-theoretic security, whereas public-key cryptography cannot. Here we demonstrate and characterize hardware to implement entanglement-based quantum digital signatures over our campus network. Over 25 hours, we collect measurements on our campus network, where we measure sufficiently low quantum bit error rates (<5% in most cases) which in principle enable quantum digital signatures at over 50 km as shown through rigorous simulation accompanied by a noise model developed specifically for our implementation. These results show quantum digital signatures can be successfully employed over deployed fiber. Moreover, our reported method provides great flexibility in the number of users, but with reduced entanglement rate per user. Finally, while the current implementation of our entanglement-based approach has a low signature rate, feasible upgrades would significantly increase the signature rate.
With the quantum computational paradigm rapidly developing across the world, new vulnerabilities on currently deployed cryptography protocols are to be taken in consideration. A possible answer to said vulnerabilities is using quantum technologies on cryptography. For a quantum-assisted cryptography protocol, key pairs can be generated via quantum state measurements. This protocol is known as quantum key distribution, of extended use for providing security against any algorithm-based attack to the keys. Ensured the key protection against eavesdroppers, a QKD-assisted protocol can focus its security analysis on party behaviour. Depending on the protocol rules and steps to follow, users can attempt attacks on it with the purpose of causing disagreement or misunderstanding between parties. In this work, we present a simulation environment for a hybrid, quantum-assisted digital signature (QDS) protocol. The configurations available for the simulated network as well as the digital signature protocol make it possible to design specific communication scenarios, such as attacks on the message integrity, forging and repudiation attempts or noisy communication across the quantum channels.