In quantum censorship, an agency oversees quantum communication in a public-domain network. The agency restricts the users communication to the free states of a quantum resource theory (QRT). Despite quantum correlations being fragile, any realistic censorship leaves behind some quantumness, raising concerns that censorship may be overcome through revival or distillation of quantum resources. Here, we introduce censorship protocols that do not require a perfect erasure of a quantum resource, but rather deem censorship successful if users are unable to restore the original quantum state using free operations. We investigate under which conditions censorship is secure, and when it might fail. Moreover, we address the issue of account sharing in quantum networks, wherein independent parties assist in transmitting quantum resources to censored users. This connects resource censorship to timely topics such as quantum catalysis and resource-assisted communication. Censorship protocols offer a novel perspective on quantum network security, that differs fundamentally from existing approaches such as quantum and post-quantum cryptography.
In quantum censorship, an agency oversees quantum communication in a public-domain network. The agency restricts the users communication to the free states of a quantum resource theory (QRT). Despite quantum correlations being fragile, any realistic censorship leaves behind some quantumness, raising concerns that censorship may be overcome through revival or distillation of quantum resources. Here, we introduce censorship protocols that do not require a perfect erasure of a quantum resource, but rather deem censorship successful if users are unable to restore the original quantum state using free operations. We investigate under which conditions censorship is secure, and when it might fail. Moreover, we address the issue of account sharing in quantum networks, wherein independent parties assist in transmitting quantum resources to censored users. This connects resource censorship to timely topics such as quantum catalysis and resource-assisted communication. Censorship protocols offer a novel perspective on quantum network security, that differs fundamentally from existing approaches such as quantum and post-quantum cryptography.
We may soon see agencies offering public access to quantum communication networks. In such networks it may be a feature that certain resources are available only to priority users or at a higher user fee, as governed by a protective agency overseeing the communication in the network. If the agency wants to restrict the general users to communicate by transmitting states that we categorize as free states of a quantum resource theory (QRT), it may employ resource-destroying channels that do not affect the free states. Such channels, however, only exist for the simplest of QRTs, putting fundamental limitations on how quantum resources can be regulated. In this work, we go beyond the present limitation by devising a nonlinear censorship protocol which makes use of classical information about the transmitted state. We study the requirement disabling malicious users from breaking the censorship. The protocol can establish an unbreakable censorship of imaginarity and entanglement, while no such censorship can be made for quantum discord and Bell nonlocality.
A protocol for regulating the distribution of quantum information between multiple parties is put forward. To prohibit the unrestricted distribution of quantum-resource states in a public quantum network, agents can apply a resource-destroying map to each sender's channel. Since resource-destroying maps only exist for affine quantum resource theories, censorship of a nonaffine resource theory is established on an operationally motivated subspace of free states. This is achieved by using what we name a resource-censoring map. The protocol is applied to censoring coherence, reference frames, and entanglement. Because of the local nature of the censorship protocol, it is, in principle, possible for collaborating parties to bypass censorship. Thus, we additionally derive necessary and sufficient conditions under which the censorship protocol is unbreakable.
Quantum networks rely on both quantum and classical channels for coordinated operation. Current architectures employ entanglement distribution and key exchange over quantum channels but often assume that classical communication is sufficiently secure. In practice, classical channels protected by traditional cryptography remain vulnerable to quantum adversaries, since large-scale quantum computers could break widely used public-key schemes and reduce the effective security of symmetric cryptography. This perspective presents a quantum-resistant network architecture that secures classical communication with post-quantum cryptographic techniques while supporting entanglementbased communication over quantum channels. Beyond cryptographic protection, the framework incorporates continuous monitoring of both quantum and classical layers, together with orchestration across heterogeneous infrastructures, to ensure end-to-end security. Collectively, these mechanisms provide a pathway toward scalable, robust, and secure quantum networks that remain dependable against both classical and quantum-era threats.
With the advancement in Internet-based technologies, network applications are no longer just limited to one-to-one communication; instead, it has become a publicly accessible resource. Regardless of this growth, such applications bring specific challenges concerning authentication, integrity, and privacy. Cryptography stands as an ideal solution to overcome these issues through an interactive method of secure communication called Key Exchange. Key exchange protocols allow two or more entities to agree upon a shared secret transmitted over a public channel without revealing any information to an eavesdropper.
This thesis contributes to the design and analysis of the variants of key exchange protocols along with their applications. As per the security requirements, the proposed schemes are either designed in an interactive model or a non-interactive model. Each scheme undergoes a series of formal and informal security analysis. The formal analysis provides simulation result using cryptographic models. Whereas, an informal analysis showcases the theoretical proves on known attacks where an adversary controls the network. The performance analysis maps the protocol’s efficiency based on the computation cost and communication size.
The first contribution introduces an interactive two-party authenticated key exchange protocol. We begin by investigating the security flaws in an existing system such as, lack of user anonymity, trace attack, clogging attack, and failure to resist replay attack. Then proposed an authenticated self-certified key exchange protocol that overcomes the addressed issues. Also, it eliminates the requirements of a trusted certificate authority to authorize the entities. The scheme achieves anonymity during session execution, mutual authentication and enables session key agreement.Based on the ideology, an application is designed, forsecure communication between ad-hoc nodes in a mobile ad-hoc network.
The second contribution contributes to the design of an Identity-based authenticated three-party key exchange protocol that overcomes the incapability of managing huge
peer-to-peer communication and high computation cost faced by two-party authenticated key exchange protocols. The proposed scheme preserves user privacy by enabling the property of anonymity and ensures non-repudiation. Based on the ideology, an application is designed to establish a secure session key between two users with the help of a trusted server for an electronic payment system.
The third contribution proposes an interactive pairing-free certificateless authenticated group key agreement scheme suitable for a resource constrained mobile network. The scheme allows any user to join or leave the group dynamically. The key agreement protocol devised in this scheme ensures un-deniability property by incorporating the signcryption, and unsigncryption algorithm.
The final contribution presents a non-interactive Identity-based deniable authentication protocol that allows an intended receiver to identify the origin of a given message without being able to prove sender’s identity to a third party.
Quantum key distribution, which allows two distant parties to share an unconditionally secure cryptographic key, promises to play an important role in the future of communication. For this reason such technique has attracted many theoretical and experimental efforts, thus becoming one of the most prominent quantum technologies of the last decades. The security of the key relies on quantum mechanics and therefore requires the users to be capable of performing quantum operations, such as state preparation or measurements in multiple bases. A natural question is whether and to what extent these requirements can be relaxed and the quantum capabilities of the users reduced. Here we demonstrate a novel quantum key distribution scheme, where users are fully classical. In our protocol, the quantum operations are performed by an untrusted third party acting as a server, which gives the users access to a superimposed single photon, and the key exchange is achieved via interaction-free measurements on the shared state. We also provide a full security proof of the protocol by computing the secret key rate in the realistic scenario of finite-resources, as well as practical experimental conditions of imperfect photon source and detectors. Our approach deepens the understanding of the fundamental principles underlying quantum key distribution and, at the same time, opens up new interesting possibilities for quantum cryptography networks
Quantum catalysts can overcome otherwise impossible quantum state transformations without being consumed, and allowing them to become correlated with the output makes this assistance substantially more powerful. This raises a fundamental question for entanglement theory: which limitations on state manipulation remain when such correlated catalysts are freely available? We answer this question in the positive-partial-transpose (PPT) resource theory, which allows a substantially broader class of operations than local operations and classical communication (LOCC). We identify general conditions under which regularized relative-entropy measures become strongly superadditive, and use them to construct monotones that constrain correlated catalytic PPT transformations without any knowledge of the catalyst. In particular, we prove that the regularized PPT relative entropy is fully additive and strongly superadditive, resolving an open problem in entanglement theory. Most importantly, these constraints show that even arbitrary correlated catalysts cannot restore asymptotic reversibility: for an explicit state, the optimal entanglement distillation rate remains strictly smaller than the entanglement cost. Thus, substantial catalytic assistance does not remove some of the fundamental limitations of mixed-state entanglement manipulation.