Unconditional security is the key-feature of quantum cryptography, which makes it superior to any classical encryption scheme. Most research in this area focuses on analyzing the theoretical properties and performance of particular quantum key distribution protocols, but a rigorous analysis on the network level seems to be missing. We present a game-theoretic approach which gives simple and tight bounds to the risk of communication that any two peers in a quantum network have to take when communicating, even if quantum cryptography is used. This work is motivated by recent (IM)possibility results regarding unconditionally secure message transmission in arbitrary networks, which puts stringent constraints on the network topology. Hence, our model naturally accounts for a given graph topology (existing fibre-optic networks which are natural candidates for a roll-out of a quantum network), as well as measuring risk in terms of probability or the designers subjective understanding. As a by-product, our model gives optimal path selection strategies, and the optimal design of network topologies under given constraints (like geographic or monetary ones).
Unconditional security is the key-feature of quantum cryptography, which makes it superior to any classical encryption scheme. Most research in this area focuses on analyzing the theoretical properties and performance of particular quantum key distribution protocols, but a rigorous analysis on the network level seems to be missing. We present a game-theoretic approach which gives simple and tight bounds to the risk of communication that any two peers in a quantum network have to take when communicating, even if quantum cryptography is used. This work is motivated by recent (IM)possibility results regarding unconditionally secure message transmission in arbitrary networks, which puts stringent constraints on the network topology. Hence, our model naturally accounts for a given graph topology (existing fibre-optic networks which are natural candidates for a roll-out of a quantum network), as well as measuring risk in terms of probability or the designers subjective understanding. As a by-product, our model gives optimal path selection strategies, and the optimal design of network topologies under given constraints (like geographic or monetary ones).
We present a general framework for casting the problem of designing secure quantum networks into a classical optimization problem. We introduce a measure of risk that serves as upper bound on the probability of loosing a message to the adversary. Based on this results, we can transform the problem of secure network design into an optimization procedure, which opens the field for the entire framework of optimization theory to tackle the problem most efficiently. The latter is particularly appealing, since we prove the problem to be NP-hard in general. Our methodology is formulated to yield results that have interpretations in probabilistic terms, but can be generalized to other settings in a straightforward manner. The modeling approach is simple, and naturally accounts for different notions of security, depending on the situation at hand. Furthermore, our results are not limited to security in quantum networks, as we rely on quantum cryptography only to the extent of securing links. Hence, the analysis is equally applicable for any (multipath) transmission setup, where information-theoretic security is demanded.
The performances of point-to-point quantum protocols is strongly dependent on the nature of the quantum channel and it rapidly deteriorates with distance. Well-known fundamental and practical limitations prevent to achieve simultaneously high rates, long distances and unconditional security. In this scenario, the rate of quantum communications between users placed at arbitrary points of a quantum communication network will strongly depend on the structure of the network, on its extension and on the nature of the communication channels. Purpose of the present work is to develop a theoretical framework to understand how the properties of the underlying network influence the rate and security of quantum communications and illustrate a potential strategy of network optimization.This work is part of the activities of the PON project “Development of quantum systems and technologies for IT security in communication networks” (QUANCOM) which aims to the realization of a metropolitan quantum communication network through the collaboration between universities, research centers and companies operating in the communication market area.
We review recent advances in the field of quantum cryptography, focusing in particular on practical implementations of two central protocols for quantum network applications, namely key distribution and coin flipping. The former allows two parties to share secret messages with information-theoretic security, even in the presence of a malicious eavesdropper in the communication channel, which is impossible with classical resources alone. The latter enables two distrustful parties to agree on a random bit, again with information-theoretic security, and with a cheating probability lower than the one that can be reached in a classical scenario. Our implementations rely on continuous-variable technology for quantum key distribution and on a plug and play discrete-variable system for coin flipping, and necessitate a rigorous security analysis adapted to the experimental schemes and their imperfections. In both cases, we demonstrate the protocols with provable security over record long distances in optical fibers and assess the performance of our systems as well as their limitations. The reported advances offer a powerful toolbox for practical applications of secure communications within future quantum networks.
The emergence of quantum computing has provided new paradigms for cryptography. On the one hand, it poses significant new threats to existing classically cryptographic systems, requiring the community to define new security models that capture what a quantum adversary can do. On the other hand, it gives us new tools to design cryptographic protocols, with weaker assumptions than in the classical world, or even protocols that are impossible classically. In this survey, we first give an overview of new security definitions for classical cryptography, considering quantum adversaries who can either only use local quantum computation (post-quantum security), or even send quantum messages and in particular have access to oracle in superposition (quantum security). We explore these new notions through the examples of commitments, zero-knowledge proofs, encryption, and signatures. Then, we present what is arguably the most famous application of quantum cryptography: quantum key distribution (QKD) protocols that take advantage of unique properties of quantum mechanics to provide secure communication unconditionally. We also explore cryptography beyond QKD, focusing on unclonable cryptography: a family of cryptographic functionalities, built with quantum states, and designed to be resistant to counterfeit by leveraging the “no-cloning” theorem. We examine in particular quantum money, but also the recent notions of unclonable encryption and copy-protection, including related variants. By presenting a comprehensive survey of these topics, this paper aims to provide a thorough understanding of the current landscape and future potential of quantum cryptography.
The emergence of quantum computing poses significant risks to conventional network security, prompting researchers to focus on developments in quantum cryptography, particularly Quantum Key Distribution (QKD).According to research, it has been found that traditional security methods, like RSA encryption, could potentially be at risk from quantum algorithms.On the other hand, quantum cryptography is a field of study that leverages the principles of quantum mechanics to improve the security of communication.One of the techniques used in quantum cryptography is Quantum Key Distribution (QKD), which makes use of the unique properties of quantum particles such as photons to securely distribute encryption keys and detect any potential eavesdropping attempts, thanks to the uncertainty principle.Nevertheless, the integration of QKD into current network infrastructures poses significant challenges due to the required technological advancements.This study offers a comprehensive analysis of the fundamental principles underlying quantum cryptography, the obstacles that arise during its implementation, and its potential prospects for protecting against the risks posed by advancements in quantum computing.Furthermore, this study delves into the potential consequences of these technological advancements across different industries and emphasizes the need to create algorithms that can withstand quantum attacks to guarantee strong data security in the age of digitalization.
Security and privacy have become such important commodities in
the information and globalization era that it would be
extremely beneficial to comprehensively explore possibilities
for providing (near) perfect performance in these fields. A
method based on quantum phenomena and the laws and limitations
of quantum information processing and communication was
recently developped with the aim of providing so-called
unconditional security in sensitive cryptographic tasks. During
the last 20 years, quantum cryptography has made remarkable
(even previously unimaginable) progress. The goal of this paper
is to present a brief introduction to the principles, methods
and achievements of quantum cryptography and to discuss its
recent advances and the challenges it poses, especially in the
area of quantum network security