Key Distribution Research Articles

Electromagnetic side-channel attack risk assessment on a practical quantum-key-distribution receiver based on multi-class classification

AbstractWhile quantum key distribution (QKD) is a theoretically secure way of growing quantum-safe encryption keys, many practical implementations are challenged due to various open attack vectors, resulting in many variations of QKD protocols. Side channels are one such vector that allows a passive or active eavesdropper to obtain QKD information leaked through practical devices. This paper assesses the feasibility and implications of extracting the raw secret key from far-field radiated emissions from the single-photon avalanche diodes used in a BB84 QKD quad-detector receiver. Enhancement of the attack was also demonstrated through the use of deep-learning model to distinguish radiated emissions due to the four polarized encoding states. To evaluate the severity of such side-channel attack, multi-class classification based on raw-data and pre-processed data is implemented and assessed. Results show that classifiers based on both raw-data and pre-processed features can discern variations of the electromagnetic emissions caused by specific orientations of the detectors within the receiver with an accuracy higher than 90%. This research proposes machine learning models as a technique to assess EM information leakage risk of QKD and highlights the feasibility of side-channel attacks in the far-field region, further emphasizing the need to utilise mechanisms to avoid electromagnetic radiation information leaks and measurement-device-independent QKD protocols.

Field experimental mode-pairing quantum key distribution with intensity fluctuations

The mode-pairing quantum key distribution (MP-QKD) protocol, which can achieve high key rates over long distances without phase locking, is a potential candidate for implementing intercity QKD. However, achieving precise control of the light source intensity in a field MP-QKD experiment is an exceedingly challenging task. In this Letter, we study the decoy-state MP-QKD protocol with light source intensity fluctuations. Furthermore, we propose a statistical analysis method based on the T-distribution to calculate confidence intervals of intensity fluctuations. Finally, in the field MP-QKD experiments, considering intensity fluctuations and the finite size effect, we obtain secure key rates of 1.03 × 10−6 bit/pair and 3.64 × 10−6 bit/pair for the symmetric (195.8 km) and asymmetric (127.7 km) cases, respectively.

Multi-Protocol Relay Chaining for Large-Scale Quantum Key Distribution Networks

Abstract As the first stage of the quantum Internet, quantum key distribution (QKD) networks hold the promise of providing long-term security for diverse users. Most existing QKD networks have been constructed based on independent QKD protocols, and they commonly rely on the deployment of single-protocol trusted relay chains for long reach. Driven by the evolution of QKD protocols, large-scale QKD networking is expected to migrate from a single-protocol to a multi-protocol paradigm, during which some useful evolutionary elements for the later stages of the quantum Internet may be incorporated. In this work, we delve into a pivotal technique for large-scale QKD networking, namely multi-protocol relay chaining. A multi-protocol relay chain is established by connecting a set of trusted/untrusted relays relying on multiple QKD protocols between a pair of QKD nodes. The structures of diverse multi-protocol relay chains are described, based on which the associated model is formulated and the policies are defined for the deployment of multi-protocol relay chains. Furthermore, we propose three multi-protocol relay chaining heuristics. Numerical simulations indicate that the designed heuristics can effectively reduce the number of trusted relays deployed and enhance the average security level versus the commonly used single-protocol trusted relay chaining methods on backbone network topologies.

Passive continuous-variable quantum key distribution based on simultaneous quantum and classical communication in the terahertz band

Passive continuous-variable quantum key distribution based on simultaneous quantum and classical communication in the terahertz band

Silicon–based integrated orbital angular momentum parity sorter

Abstract A silicon–based integrated orbital angular momentum (OAM) parity sorter using two-dimensional multimode interference (2D MMI) waveguides is designed and numerically analyzed. An OAM parity sorter, which sorts OAM modes according to their parity (even or odd) is an elegant device in a broad range of OAM states processing applications including quantum gates, quantum key distribution, generation of high dimensional quantum gates, quantum information, and teleportation. The presented three–part integrated parity sorter is realized based on the self–imaging and field–splitting properties of MMI structures. Its total length is 11 444 µm. The proposed device works for OAM modes with |l| ⩽ 5. The performance of OAM sorting is investigated with the results confirming the high purity (up to 98.33% and 94.45% at even and odd ports, respectively) for the telecommunication wavelength λ 0 = 1550 nm.

A New Tree Quantum Key Agreement Protocol for Secure Multiparty Communication

The Tree Multiparty Quantum Key Agreement Protocol (TMQKAP) is introduced as a novel solution for secure quantum key agreement among multiple participants, specifically tailored for tree topologies. Based on the BB84 protocol, TMQKAP employs hierarchical tree structures and XOR operations to facilitate efficient and secure key generation. Key elements are exchanged among participants in an equitable manner, ensuring that each participant contributes equally to the generation of the shared key. The protocol demonstrates robust security, effectively defending against both external and internal attacks, and achieves a quantum efficiency of 1/2 (N −1), where N is the number of participants. Thorough security analysis and simulations show TMQKAP’s robustness against various attacks while maintaining high efficiency. Additionally, the protocol is readily implementable with current quantum technologies, utilizing single-photon transmission to facilitate secure key distribution.

Quantum Entanglement an Indispensable Tool of Quantum Teleportation

One of the most crucial procedures in quantum information is quantum teleportation. Quantum teleportation, which makes use of the physical resource of entanglement, is a fundamental primitive in many quantum information tasks and is a crucial component of quantum technologies. It is essential to the ongoing development of quantum networks, quantum computing, and quantum communication. Here, the practical applications of Bell states, algebra of entanglement, and quantum dense coding are highlighted. The fundamentals of quantum entanglement are described, along with its characteristics and the Einstein-Poldolsky-Rosen dilemma. By separating its distinctive properties, this paper demonstrated that teleportation will be used practically for quantum key distribution in the very near future. It also revealed the fundamental theoretical concepts behind quantum teleportation.

Enhancing Security in Low-power Wide-area (LPWA) IoT Environments: The Role of HSM, Tamper-proof Technology, and Quantum Cryptography

Low-power wide-area (LPWA) networks are integral to expanding Internet of Things (IoT) applications, offering extensive coverage with low power consumption. However, these networks face significant security challenges due to their widespread deployment and inherent constraints. In order to provide secure services in an LPWA IoT environment, important information stored in IoT devices (encryption keys, device unique numbers, etc.) must be safely protected from external hacking or theft by physical access, and it is necessary to develop tamper-proof technology to enhance physical security. Meanwhile, with so many ruggedized IoT devices processing and transmitting sensitive information, security systems are essential to protect the integrity and privacy of IoT data. This paper explores the critical role of hardware security modules (HSMs), tamper-proof technology, and quantum cryptography in enhancing the physical, network, and data security of LPWA IoT environments. We propose operational strategies for HSMs, tamper-proof technology in ruggedized LPWA IoT settings, and a quantum key distribution (QKD)-based IPsec solution for robust network and data security.

Research on Quantum Key, Distribution Key and Post-quantum Cryptography Key Applied Protocols for Data Science and Web Security

Currently, data security is one of the most concerning research topics. The traditional RSA encryption system has become vulnerable to quantum algorithms such as Grover and Shor, leading to the development of new security systems for the quantum. As a result, quantum cryptography is gaining importance as a key element of future communication security. This study focuses on quantum key distribution protocols for data quantum encryption, aiming to achieve quantum robustness in all stages of quantum cryptography communication processes. Quantum cryptography communication requires robust quantum encryption not only between end-nodes but also between all components. Therefore, this study demonstrates the process of end-to-end data quantum encryption and proves the overall quantum robustness in this process.

Implementation of entropically secure encryption: Securing personal health data

AbstractEntropically secure encryption (ESE) offers unconditional security with shorter keys compared to the One‐Time Pad. Here, the first implementation of ESE for bulk encryption is presented. The main computational bottleneck for bulk ESE is a multiplication in a very large finite field. This involves multiplication of polynomials followed by modular reduction. A polynomial multiplication is implemented based on the gf2x library, with modifications that avoid inputs of vastly different length, thus improving speed. Additionally, a recently proposed efficient reduction algorithm that works for any polynomial degree is implemented. Two use cases are investigated: x‐ray images of patients and human genome data. Entropy estimation is conducted using compression methods whose results determine the key lengths required for ESE. The running times for all steps of the encryption are reported. The potential of ESE to be used in conjunction with quantum key distribution (QKD), in order to achieve full information‐theoretic security of QKD‐protected links for these use cases is discussed.

Robust continuous-variable quantum key distribution in the finite-size regime

Quantum key distribution (QKD) has been proven to be theoretically unconditionally secure. However, any theoretical security proof relies on certain assumptions. In QKD, the assumption in the theoretical proof is that the security of the protocol is considered under the asymptotic case where Alice and Bob exchange an infinite number of signals. In the continuous-variable QKD (CV-QKD), the finite-size effect imposes higher requirements on block size and excess noise control. However, the local local oscillator (LLO) CV-QKD system cannot be considered time-invariant under long blocks, especially in cases of environmental disturbances. Thus, we propose an LLO CV-QKD scheme with time-variant parameter estimation and compensation. We first establish an LLO CV-QKD theoretical model under the temporal modes of continuous-mode states. Then, a robust method is used to compensate for arbitrary frequency shift and arbitrary phase drift in CV-QKD systems with longer blocks, which cannot be achieved under traditional time-invariant parameter estimation. Besides, the digital signal processing method predicated on high-speed reference pilots can achieve a time complexity of O(1). In the experiment, the frequency shift is up to 89.05 MHz/s and phase drift is up to 3.036 Mrad/s using a piezoelectric transducer (PZT) to simulate the turbulences in the practical channel. With a signal-to-interference ratio (SIR) of −51.67 dB, we achieve a secret key rate (SKR) of 0.29 Mbits/s with an attenuation of 16 dB or a standard fiber of 80 km. This work paves the way for future long-distance field-test experiments in the finite-size regime.

Assessing the Impact of Cryptography on the Security of Wireless Ad Hoc Networks

The use of wireless networks for communication in bistros, airports, hotels, offices, colleges, and other public locations is increasing as they become more widespread. Although remote organisations and its applications are becoming increasingly widely recognised, security concerns related to them have grown to be of great concern. In this investigation, we'll develop a different plan to implement quantum cryptography for key distribution in 802.11 companies. They are helpful because of their adaptability and quick data transfer in residences, workplaces, and businesses. Given the principles of material science, quantum cryptography enables unfettered security for the exchange of cryptographic keys between two distant meetings. This investigation's main goal is to investigate potential vulnerabilities and security concerns in remote organization correspondence and give a structure to unqualified security in remote systems administration utilizing quantum key dispersion (QKD).

Quantum Cryptography for Secure Communications and the Enhancement of U.S. Cybersecurity in the Quantum Age

This paper explores the critical role of quantum cryptography in enhancing U.S. cybersecurity, focusing on its potential to counteract the growing threats posed by quantum computing. As quantum computers advance, classical encryption methods like RSA and AES face unprecedented vulnerabilities. Quantum Key Distribution (QKD) offers a groundbreaking solution by leveraging quantum mechanics to secure data transmission. The paper evaluates current implementations and future challenges of quantum cryptography, emphasizing its importance for government, military, financial, and healthcare sectors in safeguarding sensitive communications in the quantum age.

Loss tolerance quantum key distribution based on the signal extraction model and advantage distillation technology

Compared with traditional networks, quantum key distribution (QKD) offers the ultimate resources, allowing two remote users to share secret symmetric keys regardless of the capabilities of eavesdroppers. However, the widespread application of commercial QKD is still challenging due to the low photon detection efficiency and the extremely high transmission loss. Here we demonstrate a fully commercial phase-encoding QKD system using a signal extraction model and advantage distillation technology to suppress detector noise and perform real-time pre-error correction. 1.89 × 10−10 in the asymptotic case and 7.43 × 10−12 in the nonasymptotic case secret key bits per pulse are achieved with a total loss of 70.05 dB. This method not only increases the transmission loss tolerance but also provides a more realistic deployment of quantum communication.

Efficient Implementation of Interior-Point Methods for Quantum Relative Entropy

Quantum relative entropy (QRE) programming is a recently popular and challenging class of convex optimization problems with significant applications in quantum computing and quantum information theory. We are interested in modern interior-point (IP) methods based on optimal self-concordant barriers for the QRE cone. A range of theoretical and numerical challenges associated with such barrier functions and the QRE cones have hindered the scalability of IP methods. To address these challenges, we propose a series of numerical and linear algebraic techniques and heuristics aimed at enhancing the efficiency of gradient and Hessian computations for the self-concordant barrier function, solving linear systems, and performing matrix-vector products. We also introduce and deliberate about some interesting concepts related to QRE such as symmetric quantum relative entropy. We design a two-phase method for performing facial reduction that can significantly improve the performance of QRE programming. Our new techniques have been implemented in the latest version (DDS 2.2) of the software package Domain-Driven Solver (DDS). In addition to handling QRE constraints, DDS accepts any combination of several other conic and nonconic convex constraints. Our comprehensive numerical experiments encompass several parts, including (1) a comparison of DDS 2.2 with Hypatia for the nearest correlation matrix problem, (2) using DDS 2.2 for combining QRE constraints with various other constraint types, and (3) calculating the key rate for quantum key distribution (QKD) channels and presenting results for several QKD protocols. History: Accepted by Giacomo Nannicini, Area Editor for Quantum Computing and Operations Research. Accepted for Special Issue. Funding: This work was supported by the National Science Foundation [Grant CMMI-2347120] and Discovery Grants from the Natural Sciences and Engineering Research Council of Canada. Supplemental Material: The software that supports the findings of this study is available within the paper and its Supplemental Information ( https://pubsonline.informs.org/doi/suppl/10.1287/ijoc.2024.0570 ) as well as from the IJOC GitHub software repository ( https://github.com/INFORMSJoC/2024.0570 ). The complete IJOC Software and Data Repository is available at https://informsjoc.github.io/ .

Modified general individual attack against differential-phase-shift quantum key distribution

Modified general individual attack against differential-phase-shift quantum key distribution

Postselection Technique for Optical Quantum Key Distribution with Improved de Finetti Reductions

The postselection technique is an important proof technique for proving the security of quantum key distribution protocols against coherent attacks via the uplift of any security proof against independent identically distributed collective attacks. In this work, we go through multiple steps to rigorously apply the postselection technique to optical quantum key distribution protocols. First, we place the postselection technique on a rigorous mathematical foundation by fixing a technical flaw in the original postselection paper. Second, we extend the applicability of the postselection technique to prepare-and-measure protocols by using a de Finetti reduction with a fixed marginal. Third, we show how the postselection technique can be used for decoy-state protocols by tagging the source. Finally, we extend the applicability of the postselection technique to realistic optical setups by developing a new variant of the flag-state squasher. We also improve existing de Finetti reductions, which reduce the effect of using the postselection technique on the key rate. These improvements can be more generally applied to other quantum information processing tasks. As an example to demonstrate the applicability of our work, we apply our results to the time-bin-encoded three-state protocol. We observe that the postselection technique performs better than all other known proof techniques against coherent attacks. Published by the American Physical Society 2024

Preparing a commercial quantum key distribution system for certification against implementation loopholes

Preparing a commercial quantum key distribution system for certification against implementation loopholes

Research on time-division multiplexing for error correction and privacy amplification in post-processing of quantum key distribution

The post-processing of quantum key distribution mainly includes error correction and privacy amplification. The error correction algorithms and privacy amplification methods used in the existing quantum key distribution are completely unrelated. Based on the principle of correspondence between error-correcting codes and hash function families, we proposed the idea of time-division multiplexing for error correction and privacy amplification for the first time. That is to say, through the common error correction algorithms and their corresponding hash function families or the common hash function families and their corresponding error-correcting codes, error correction and privacy amplification can be realized by time-division multiplexing with the same set of devices. In addition, we tested the idea from the perspective of error correction and privacy amplification, respectively. The analysis results show that the existing error correction algorithms and their corresponding hash function families or the common privacy amplification methods and their corresponding error-correcting codes cannot realize time-division multiplexing for error correction and privacy amplification temporarily. However, according to the principle of correspondence between error-correcting codes and hash function families, the idea of time-division multiplexing is possible. Moreover, the research on time-division multiplexing for error correction and privacy amplification has some practical significance. Once the idea of time-division multiplexing is realized, it will further reduce the calculation and storage cost of the post-processing process, reduce the deployment cost of quantum key distribution, and help to remote the practical engineering of quantum key distribution.

Unmasking the polygamous nature of quantum nonlocality

Quantum mechanics imposes limits on the statistics of certain observables. Perhaps the most famous example is the uncertainty principle. Similar trade-offs also exist for the simultaneous violation of multiple Bell inequalities. In the simplest case of three observers, it has been shown that if two observers violate a Bell inequality, then none of them can violate any Bell inequality with the third observer, a property called monogamy of Bell violations. Forms of Bell monogamy have been linked to the no-signaling principle, and the inability of simultaneous violations of all inequalities is regarded as their fundamental property. Here, we show that the Bell monogamy does not hold universally and that in fact the only monogamous situation exists for only three observers. Consequently, the nature of quantum nonlocality is truly polygamous. We present a systematic methodology for identifying quantum states, measurements, and tight Bell inequalities that do not obey the monogamy principle for any number of more than three observers. The identified polygamous inequalities enable any subset of [Formula: see text] observers to reveal nonlocality, which is also shown experimentally by measuring Bell-type correlations of six-photon Dicke states. Our findings may be exploited for multiparty quantum key distribution as well as simultaneous self-testing of multiple nodes in quantum networks.