Ensuring the security of digital communication and data transfer has become essential in the modern era. Classical cryptographic techniques are increasingly vulnerable due to advances in quantum technologies and algorithms. Consequently, quantum computers and quantum communication offer promising solutions for secure data transfer and encryption. This study explores the generation of Quantum Digital Signatures (QDS) using Quantum Continuous Variables (QCV), providing a novel approach to secure digital signature technologies. The paper outlines the core principles of QDS generation with QCV, detailing the signature creation and verification processes. It highlights the advantages of this technology in secure communication and data transfer and discusses potential security vulnerabilities and future development prospects. Quantum Continuous Variables (QCVs), typically used in quantum optical systems, represent physical quantities with continuous spectra, such as the wavelength or phase of light. These variables enable efficient and secure quantum information processing and communication. Despite significant progress in quantum cryptography protocols using QCVs, practical application and optimization of these technologies face numerous challenges. These include complexities in preparing and measuring quantum states, managing quantum errors, and achieving higher efficiency and security standards. Moreover, the practical applications of QCV in industrial contexts remain limited, highlighting the need for further experimental and applied research. The methodology for generating QDS using QCVs involves employing specific quantum states, such as coherent and squeezed states. The process includes key distribution, signature creation and verification, and addressing potential quantum attacks. The system model comprises a sender (Alice), a receiver (Bob), and an arbiter (Charlie), facilitating secure and authenticated message transmission.
Ensuring the security of digital communication and data transfer has become essential in the modern era. Classical cryptographic techniques are increasingly vulnerable due to advances in quantum technologies and algorithms. Consequently, quantum computers and quantum communication offer promising solutions for secure data transfer and encryption. This study explores the generation of Quantum Digital Signatures (QDS) using Quantum Continuous Variables (QCV), providing a novel approach to secure digital signature technologies. The paper outlines the core principles of QDS generation with QCV, detailing the signature creation and verification processes. It highlights the advantages of this technology in secure communication and data transfer and discusses potential security vulnerabilities and future development prospects. Quantum Continuous Variables (QCVs), typically used in quantum optical systems, represent physical quantities with continuous spectra, such as the wavelength or phase of light. These variables enable efficient and secure quantum information processing and communication. Despite significant progress in quantum cryptography protocols using QCVs, practical application and optimization of these technologies face numerous challenges. These include complexities in preparing and measuring quantum states, managing quantum errors, and achieving higher efficiency and security standards. Moreover, the practical applications of QCV in industrial contexts remain limited, highlighting the need for further experimental and applied research. The methodology for generating QDS using QCVs involves employing specific quantum states, such as coherent and squeezed states. The process includes key distribution, signature creation and verification, and addressing potential quantum attacks. The system model comprises a sender (Alice), a receiver (Bob), and an arbiter (Charlie), facilitating secure and authenticated message transmission.
Digital signatures ensure the integrity of a classical message and the authenticity of its sender. Despite their far-reaching use in modern communication, currently used signature schemes rely on computational assumptions and will be rendered insecure by a quantum computer. We present a quantum digital signatures (QDS) scheme whose security is instead based on the impossibility of perfectly and deterministically distinguishing between quantum states. Our continuous-variable (CV) scheme relies on phase measurement of a distributed alphabet of coherent states and allows for secure message authentication against a quantum adversary performing collective beamsplitter and entangling-cloner attacks. Crucially, in the CV setting we allow for an eavesdropper on the quantum channels and yet retain shorter signature lengths than previous protocols with no eavesdropper. This opens up the possibility to implement CV QDS alongside existing CV quantum key distribution platforms with minimal modification.
In the first half of this Thesis, we introduce a framework of “quantum cryptographic agility,” which allows for a resource-efficient swap of an underlying cryptographic protocol. Specifically, we introduce several schemes which perform the tasks of Digital Signatures and Secret Sharing. Our first achievement is an investigation of Quantum Digital Signatures (QDS) over a continuous-variables platform, consisting of phase-encoded coherent states and heterodyne phase detection. QDS allows for secure authentication of a classical message, while guaranteeing message transferability. For the first time, we prove security of CV QDS in the presence of an eavesdropper on the quantum channels. We then introduce a continuous variable (CV) Quantum Secret Sharing (QSS) protocol. Our security proof allows for classical information to be split and shared between multiple potentially dishonest recipients, while retaining security against collective beamsplitter and entangling-cloner attacks. In the last chapter of this half, we introduce another QDS scheme which runs over identical hardware setup to our QSS protocol. We analyse experimental data in which quantum coherent states were distributed at a rate of 1 GHz, which for QDS allows us to securely sign a message in less than 0.05 ms. In the second half of this Thesis we suggest and discuss a deterministic source of nonclassical light, which we call “PhoG”. Our source is based on the coherent diffusive photonics, relying on both coherent and dissipative evolution of the quantum state, and may be realised in an array of dissipatively-coupled laser-inscribed waveguides in a χ⁽³⁾ glass. We analyse the PhoG device with several analytical and numerical models and demonstrate that a coherent state input leads to a bright output state with strong photon-number squeezing. With minor reconfiguration our system can generate entanglement between spatially separated modes via a process analogous to four-wave mixing.
Electronic Health Records (EHRs) form the backbone of modern healthcare, ensuring seamless access to a patient’s medical history and fostering effective patient-doctor relationships. Their digital nature, however, exposes them to myriad security threats, including unauthorized access, tampering, and fraudulent alterations. Traditional cryptographic techniques, while effective in the current digital landscape, might not stand robust against future threats, especially those posed by quantum computers. This paper introduces Quantum Digital Signatures (QDS) as a cutting-edge approach to address this burgeoning concern. QDS leverages the principles of quantum mechanics to provide an additional layer of security, making it computationally infeasible for adversaries to forge or alter signed messages, including sensitive EHR data. Unlike conventional digital signatures that depend on the presumed difficulty of certain mathematical problems, the security attributes of QDS stem from the fundamental laws of quantum physics, ensuring a higher level of integrity and authenticity. We present a comprehensive overview of the QDS protocol and its integration into current EHR systems. Our comparative analysis with existing cryptographic techniques illuminates the advantages of QDS, especially in preventing undetected alterations and ensuring non-repudiation. Practical deployment challenges, including quantum device imperfections and potential integration bottlenecks, are also addressed. The adoption of Quantum Digital Signatures in safeguarding EHRs ushers in a new era of medical data security. While the large-scale implementation of such quantum technologies is still in its infancy, proactive research and early adoption are pivotal in preparing healthcare systems for future challenges. Through this research, we advocate for the broader integration of quantum cryptographic techniques, such as QDS, to uphold the sanctity and trustworthiness of electronic medical data in the face of evolving digital threats.
Quantum image encryption (QIE) has emerged as a promising solution for securing digital data in an era dominated by rapid advancements in quantum computing and increasing cyber threats. Traditional cryptographic techniques, which rely on classical encryption methods, are vulnerable to the computational power of quantum algorithms, posing significant challenges for maintaining data privacy and integrity. This survey presents a thorough review of quantum encryption techniques, highlighting both their limitations and advantages, with a particular emphasis on their ability to ensure secure visual data transmission in the post-quantum era. Additionally, it provides a comparative analysis of classical and quantum cryptographic techniques, with a primary focus on quantum encryption methods. The survey also explores potential solutions to address the challenges inherent in classical encryption schemes, highlighting how these challenges can be mitigated through quantum encryption approaches. As quantum computing continues to evolve, the need for quantum-secure encryption methods becomes more critical. This survey not only highlights the innovative techniques that show promise for future secure visual data transmission but also identifies key areas for future research and development, paving the way for robust and scalable solutions in the quantum computing era.
Abstract A quantum digital signature (QDS) is guaranteed by the laws of quantum physics and can provide unconditional security to authenticate classical messages. Previous QDS protocols that shared secret keys could be realized using discrete-variable quantum key distribution (DV-QKD), for which the DV-QKD relied on extreme requirements like single-photon detection and extremely weak pulses of light. QDS protocols are mainly focused on how to sign a one-bit message rather than multi-bit messages. In this paper, we present a continuous-variable quantum digital signature (CV-QDS) protocol for signing multi-bit messages. The CV-QDS protocol has better compatibility with existing communication systems and the encoding strategy for multi-bit messages is simpler than before. We hope the continuous-variable protocol could further improve the performance of QDS.
The quantum digital signature (QDS) has attracted much attention as it ensures the nonrepudiation, unforgeability, and transferability of signature messages based on information-theoretic security. Amiri et al. ( Phys. Rev. A 93 032325 ) proposed the first practical QDS protocol based on orthogonal coding, which has realized information-theoretic security and become the mainstream paradigm in QDS research. The procedure of QDS involves two essential stages, the one is the distribution stage, in which Alice-Bob and Alice-Charlie individually utilize the three-intensity decoy-state quantum key distribution protocol but without error correction or privacy amplification, namely, key-generation protocol, to generate correlated bit strings, the other is the messaging stage, in which Alice transmits signature messages to the two recipients. However, previous theoretical and experimental studies both overlooked the modulation errors that may be introduced in the state preparation process due to the imperfections in modulator devices. Under the traditional framework of GLLP analysis method, these errors will significantly reduce the actual signature rates. Therefore, we propose a state-preparation-error tolerant QDS and use parameter analysis to characterize the state preparation error to make the simulation analysis more realistic. In addition, we analyze the signature rates of the present scheme by using the three-intensity decoy-state method. Compared with previous QDS protocols, our protocol almost shows no performance degradation under practical state preparation errors and exhibits a maximum transmission distance around 180 km. Furthermore, state preparation errors do not have a significant influence on the bit error rate induced by normal communication between the legitimate users or the one produced by an eavesdropper. These results prove that the method proposed in this paper has excellent robustness against state preparation errors and it can achieve much higher signature rates and signature distances than other standard methods. Besides, signature rates are basically unchanged under different total pulse numbers, which shows that our protocol also has good robustness against the finite-size effect. Additionally, in the key generation process, our method is only required to prepare three quantum states, which will reduce the difficulty of experiment realizations. Furthermore, the proposed method can also be combined with the measurement-device-independent QDS protocol and the twin-field QDS protocol to further increase the security level of QDS protocol. Therefore, our work will provide an important reference value for realizing the practical application of QDS in the future.