Quantum cryptography promises information theoretic security of several cryptographic primitives. Most of the proposed security proofs work in an ideal communication scenario where all messages are correctly delivered after the first attempt. However, real networks are subject to message losses and require retransmissions to cope with them. While the latter is hardly ever a problem in classical cryptography, with quantum communication copy-and-retransmit could be impossible due to the famous no-cloning theorem. In this work, we analyze some quantum cryptoschemes such as public-key encryption, authentication and quantum money, assuming that quantum messages may be lost as they travel through the communication medium. Although all these schemes are theoretically secure, we show that this degree of realism renders some protocols insecure or impractical, while others are completely unaffected. When possible, we provide mitigations such as teleportation or protocol modifications to circumvent these challenges.
Quantum cryptography promises information theoretic security of several cryptographic primitives. Most of the proposed security proofs work in an ideal communication scenario where all messages are correctly delivered after the first attempt. However, real networks are subject to message losses and require retransmissions to cope with them. While the latter is hardly ever a problem in classical cryptography, with quantum communication copy-and-retransmit could be impossible due to the famous no-cloning theorem. In this work, we analyze some quantum cryptoschemes such as public-key encryption, authentication and quantum money, assuming that quantum messages may be lost as they travel through the communication medium. Although all these schemes are theoretically secure, we show that this degree of realism renders some protocols insecure or impractical, while others are completely unaffected. When possible, we provide mitigations such as teleportation or protocol modifications to circumvent these challenges.
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.
Widely used communication and messaging protocols, e.g., TLS 1.3 and Signal, are insecure against an adversary with a quantum computer. We expect that post-quantum security will become mandatory for a new generation of cryptographic protocols in the nearest 10-15 years. The analysis of existing post-quantum secure cryptographic tools for key exchange, encryption and message authentication based on hard problems in codes, lattices, ring learning with errors and elliptic curve isogenies revealed their advantages and drawbacks. In particular, we conclude, that the main threat to communication and messaging protocols is only pre-quantum security of currently used Diffie-Hellman key exchange protocols. We summarize efficiency and safety results for each class of post-quantum cryptographic schemes and present an experimental implementation of isogeny-based Diffie-Hellman-like key exchange protocol as an illustration of their applicability.
The rapid advancement of quantum computing poses a significant threat to classical cryptographic systems that rely on the computational hardness of mathematical problems such as integer factorization and discrete logarithm problems. In this context, quantum cryptography has emerged as a promising paradigm for secure communication based on the fundamental principles of quantum mechanics rather than on computational assumptions. This paper presents a comprehensive review of quantum cryptography, with a particular focus on Quantum Key Distribution (QKD), the most mature application. The study discusses the theoretical foundations of quantum security, including superposition, entanglement, and the No-cloning theorem, which collectively enable eavesdropping detection and guarantee information-theoretic security. Furthermore, the review examines major QKD protocols, such as BB84 and E91, as well as their advanced variants designed to address practical vulnerabilities and enhance performance. Recent progress in real-world implementations, including fiber-optic networks, free-space communication, and satellite-based systems such as the Micius satellite, is also analyzed. In addition, the paper highlights critical challenges related to scalability, hardware limitations, and security loopholes arising from imperfect devices. Finally, emerging research directions, including hybrid cryptographic frameworks that integrate quantum and post-quantum approaches, are discussed to provide insights into the future of secure communication. This review aims to provide a structured, up-to-date understanding of quantum cryptography, bridging the gap between theoretical developments and practical implementations, and emphasizing its crucial role in shaping next-generation cybersecurity systems.
Quantum cryptography promises a revolutionary transformation in secure data transmission by leveraging fundamental principles of quantum mechanics such as superposition, entanglement, and no-cloning. As classical encryption methods face increasing vulnerabilities from powerful adversaries and emerging quantum computers, Quantum Key Distribution (QKD) and quantum-resistant algorithms offer unprecedented security advantages. This article explores the future landscape of quantum cryptography, analyzing QKD protocols, post-quantum cryptographic models, hardware requirements, communication architectures, and the evolving threat landscape. Two graphs illustrate the growth of global QKD deployment and the performance comparison of classical vs. quantum-resistant encryption schemes. Key challenges—including scalability, interoperability, cost, and standardization—are discussed alongside future opportunities in hybrid quantum-classical secure networks. The article concludes with a forward-looking assessment of how quantum cryptography will reshape secure communication in the coming decade.
Public-key cryptosystems for quantum messages are considered from two aspects: public-key encryption and public-key authentication. Firstly, we propose a general construction of quantum public-key encryption scheme, and then construct an information-theoretic secure instance. Then, we propose a quantum public-key authentication scheme, which can protect the integrity of quantum messages. This scheme can both encrypt and authenticate quantum messages. It is information-theoretic secure with regard to encryption, and the success probability of tampering decreases exponentially with the security parameter with regard to authentication. Compared with classical public-key cryptosystems, one private-key in our schemes corresponds to an exponential number of public-keys, and every quantum public-key used by the sender is an unknown quantum state to the sender.
Communications in secrecy are often required in many commercial and military applications. Unfortunately, many cryptographic schemes in use today such as public-key cryptography based on the RSA algorithm would be broken with either unanticipated advances in hardware and algorithm or the advent of quantum computers. Quantum cryptography, on the other hand, has been proven secure even against the most general attack allowed by the laws of physics and is a promising technology poised for widespread adoption in realistic cryptographic applications. Quantum cryptography allows two parties to expand on a secret key that they have previously shared. Various quantum cryptographic protocols have been proposed to perform this task. In this paper, we survey some popular quantum cryptographic protocols (including the famous Bennett-Brassard 1984 protocol) and discuss their security. Specifically, we consider their security in two cases: the ideal case where a perfect single-photon source is used and the practical case where a realistic laser source is used. We compare the protocols and find that the efficient six-state protocol outperforms the others both in the tolerable quantum bit error rate and in the key generation rate when a realistic laser source is used.