The stability of quantum key distribution systems is based not only on the detection of attacks on quantum states, which is guaranteed by the fundamental quantum theory laws, but also on ensuring the integrity of classical messages transmitted through an auxiliary classical communication channel. To detect attacks on the classic communication channel, the authentication procedure is used. Information-theoretic authentication guarantees the detection of attacks on the classical communication channel regardless of the computational and technical capabilities of an eavesdropper, including the quantum computer. The fundamental quantum cryptographic relationship between the abstract criterion of the robustness of quantum key distribution systems with theoretical-information authentication and the quantum key search complexity has been determined for the first time using simple means.
The stability of quantum key distribution systems is based not only on the detection of attacks on quantum states, which is guaranteed by the fundamental quantum theory laws, but also on ensuring the integrity of classical messages transmitted through an auxiliary classical communication channel. To detect attacks on the classic communication channel, the authentication procedure is used. Information-theoretic authentication guarantees the detection of attacks on the classical communication channel regardless of the computational and technical capabilities of an eavesdropper, including the quantum computer. The fundamental quantum cryptographic relationship between the abstract criterion of the robustness of quantum key distribution systems with theoretical-information authentication and the quantum key search complexity has been determined for the first time using simple means.
Abstract In addition to the quantum channel, an auxiliary classical authentic communication channel is required for quantum key distribution. To provide unconditional security in quantum cryptography, which based on the fundamental laws of quantum mechanics, information-theoretic authentication is required, and not authentication based on computational complexity. The paper provides a security proof of information-theoretic authentication in quantum cryptography using ɛ -ASU 2 hash functions. The internal structure of ɛ -ASU 2 hash functions is not used in the proof, so these hash functions can be implemented by a different composition of other hash functions, for example, including the composition ɛ -AXU 2 functions with a reused key and subsequent encryption of the tag with a one-time pad key, which is taken from the previous session of quantum key distribution. It is also shown that information-theoretic authentication preserves composable security of the keys. This authentication method can also be used for key agrrement in in networks with trusted nodes (Molotkov 2022 Laser Phys. Lett. 19 045201–9; Arbekov and Molotkov 2020 Laser Phys. Lett. 17 055202–8) and with quantum key distribution.
The proof of the security of quantum key distribution is a rather complex problem. Security is defined in terms different from the requirements imposed on keys in classical cryptography. In quantum cryptography, the security of keys is expressed in terms of the closeness of the quantum state of an eavesdropper after key distribution to an ideal quantum state that is uncorrelated to the key of legitimate users. A metric of closeness between two quantum states is given by the trace metric. In classical cryptography, the security of keys is understood in terms of, say, the complexity of key search in the presence of side information. In quantum cryptography, side information for the eavesdropper is given by the whole volume of information on keys obtained from both quantum and classical channels. The fact that the mathematical apparatuses used in the proof of key security in classical and quantum cryptography are essentially different leads to misunderstanding and emotional discussions [1]. Therefore, one should be able to answer the question of how different cryptographic robustness criteria are related to each other. In the present study, it is shown that there is a direct relationship between the security criterion in quantum cryptography, which is based on the trace distance determining the distinguishability of quantum states, and the criterion in classical cryptography, which uses guesswork on the determination of a key in the presence of side information.
Quantum cryptography Ð quantum key distribution (QKD) Ð was one of the first fields of study of quantum information theory.It reached a mature scientific level and has been implemented in commercial systems for secure quantum communications.The key distribution problem is the central issue of symmetric cryptography.Quantum cryptography solves this problem on the basis of the fundamental laws of nature: the principles of quantum mechanics.Quantum key distribution is essentially matching two independent random sequences on the transmitting and receiving sides by exchanging quantum states.Required in addition to the quantum channel is an authentic classical communication channel.Both communication channels are open and vulnerable to a perpetrator's attack.To ensure the authenticity of the classical channel at initial system startup, a seed key is required, which is used to provide information-theoretic authentication.In essence, quantum cryptography systems are mechanisms for expanding this seed key.Subsequent sessions generate a quantum key, part of which is used for authentication, while another part is employed for other cryptographic purposes, such as encryption.An issue fundamental for quantum cryptography is the number of quantum key distribution sessions that can be conducted from the initial system launch until a new system reboot, when the cryptographic properties of the quantum keys reach a critical level, after which they can no longer be used for cryptographic purposes, and a new system reboot is needed.Although a number of reviews on quantum cryptography are currently available, this issue has not been discussed in detail.It is shown that for realistic parameters of quantum cryptography systems that are currently achievable, a QKD system can operate for I.
The security of cryptographic keys in quantum cryptography systems is guaranteed by fundamental quantum mechanical exclusion principles. A quantum channel through which quantum states are transferred is not controlled and an eavesdropper can perform any modifications with it. The security of quantum key distribution protocols has already been proved [M. Tomamichel et al., Nature Commun. 3 , 634 (2011); S. N. Molotkov, J. Exp. Theor. Phys. 115 , 969 (2012)], including the realistic case of a finite length of transmitted sequences. It is always assumed that the eavesdropper has neither direct nor indirect access to the transmitting and receiving equipment. The real situation is somewhat different. The preparation and detection of quantum states occur according to random sequences that are generated on the transmitter and receiver sides. Detecting electromagnetic radiation generated in these processes, the eavesdropper can obtain additional information on a key. The upper quantum-mechanical bound on the amount of information of the eavesdropper on the key that can be obtained through a side channel has been determined.
Quantum cryptography promises secure communication protocols that surpass the limitations of classical cryptography. By leveraging the principles of quantum mechanics, particularly the phenomenon of quantum entanglement and the uncertainty principle, quantum cryptography protocols offer provable security guarantees against eavesdropping attacks. In this paper, we provide an overview of quantum cryptography, discussing its theoretical foundations, key protocols such as quantum key distribution (QKD), and experimental implementations. We highlight the advantages of quantum cryptography over classical cryptographic techniques and explore its potential applications in secure communication networks, financial transactions, and data privacy. Furthermore, we discuss ongoing research efforts and challenges in the practical deployment of quantum cryptography systems, including the development of robust quantum hardware and the integration of quantum cryptographic protocols into existing communication infrastructures. Overall, quantum cryptography holds great promise for enabling secure communication channels that are resilient to quantum attacks, paving the way for a new era of ultra-secure information exchange.
Existing quantum key distribution protocols require classical channel and classical authentication procedure. We present an alternative quantum key distribution technique which not only can operate without the requirement of classical channel and classical authentication procedure but also rejects the use of the two. This key distribution technique can act as quantum authentication protocol. Quantum cryptography [1-6] and teleportation [7] are the two facets of quantum communication. Of these two, quantum cryptography has been developed out of practical necessity- classical cryptosytems are either secure but impractical or insecure but practical [8]. Around 1970, Wiesner [1] first realised that laws of quantum mechanics can ensure security. In 1984, this radical idea took shape when Bennett and Brassad [2] invented quantum key distribution (QKD) protocol. At present many QKD protocols exist; they can be classified as EPR and non EPR protocols. The common aspects of all these protocols are that pure