Let us consider a situation where two information brokers, whose currency is, of course, information, need to reciprocally exchange information. The two brokers, being somewhat distrustful, would like a third, mutually trusted entity to be involved in the exchange process so as to guarantee the successful completion of the transaction and also verify that it indeed took place. Can this be completed in such a way that both brokers receive their information simultaneously and securely, without the trusted intermediary knowing the exchanged information? This work presents and rigorously analyzes a new quantum entanglement-based protocol that provides a solution to the above problem. The proposed protocol is aptly named the entanglement-based reciprocal simultaneous information exchange protocol. Its security is ultimately based on the assumption of the existence of a third, trusted party. Although the reciprocal information flow is between our two information brokers, the third entity plays a crucial role in mediating this process by being a guarantor and a verifier. The phenomenon of quantum entanglement is the cornerstone of this protocol, as it makes its implementation possible even when all entities are spatially separated and ensures that, upon completion, the trusted third party remains oblivious to the actual information that was exchanged.
Let us consider a situation where two information brokers, whose currency is, of course, information, need to reciprocally exchange information. The two brokers, being somewhat distrustful, would like a third, mutually trusted entity to be involved in the exchange process so as to guarantee the successful completion of the transaction and also verify that it indeed took place. Can this be completed in such a way that both brokers receive their information simultaneously and securely, without the trusted intermediary knowing the exchanged information? This work presents and rigorously analyzes a new quantum entanglement-based protocol that provides a solution to the above problem. The proposed protocol is aptly named the entanglement-based reciprocal simultaneous information exchange protocol. Its security is ultimately based on the assumption of the existence of a third, trusted party. Although the reciprocal information flow is between our two information brokers, the third entity plays a crucial role in mediating this process by being a guarantor and a verifier. The phenomenon of quantum entanglement is the cornerstone of this protocol, as it makes its implementation possible even when all entities are spatially separated and ensures that, upon completion, the trusted third party remains oblivious to the actual information that was exchanged.
This paper presents a new quantum protocol designed to transmit information from one source to many recipients simultaneously. The proposed protocol, which is based on the phenomenon of entanglement, is completely distributed and is provably information-theoretically secure. Numerous existing quantum protocols guarantee secure information communication between two parties but are not amenable to generalization in situations where the source must transmit information to two or more recipients. Hence, they must be executed sequentially two or more times to achieve the desired goal. The main novelty of the new protocol is its extensibility and generality to situations involving one party that must simultaneously communicate different, in general, messages to an arbitrary number of spatially distributed parties. This is achieved in the special way employed to encode the transmitted information in the entangled state of the system, one of the distinguishing features compared with previous protocols. This protocol can prove expedient whenever an information broker, say, Alice, must communicate distinct secret messages to her agents, all in different geographical locations, in one go. Due to its relative complexity compared with similar cryptographic protocols, as it involves communication among n parties and relies on |GHZn⟩ tuples, we provide an extensive and detailed security analysis so as to prove that it is information-theoretically secure. Finally, in terms of its implementation, the prevalent characteristics of the proposed protocol are its uniformity and simplicity, because it only requires CNOT and Hadamard gates and the local quantum circuits are identical for all information recipients.
Quantum dual-signature means that two signed quantum messages are combined and expected to be sent to two different recipients. A quantum signature requires the cooperation of two verifiers to complete the whole verification process. As an important quantum signature aspect, the trusted third party is introduced to the current protocols, which affects the practicability of the quantum signature protocols. In this paper, we propose a quantum dual-signature protocol without arbitrator and entanglement for the first time. In the proposed protocol, two independent verifiers are introduced, here they may be dishonest but not collaborate. Furthermore, strongly nonlocal orthogonal product states are used to preserve the protocol security, i.e., no one can deny or forge a valid signature, even though some of them conspired. Compared with existing quantum signature protocols, this protocol does not require a trusted third party and entanglement resources.
This article introduces the innovative Quantum Dining Information Brokers Problem, presenting a novel entanglement-based quantum protocol to address it. The scenario involves n information brokers, all located in distinct geographical regions, engaging in a metaphorical virtual dinner. The objective is for each broker to share a unique piece of information with all the others simultaneously. Unlike previous approaches, this protocol enables a fully parallel, single-step communication exchange among all the brokers, regardless of their physical locations. A key feature of this protocol is its ability to ensure that both the anonymity and privacy of all the participants are preserved, meaning that no broker can discern the identity of the sender of any received information. At its core, the Quantum Dining Information Brokers Problem serves as a conceptual framework for achieving anonymous, untraceable, and massively parallel information exchange in a distributed system. The proposed protocol introduces three significant advancements. First, while quantum protocols for one-to-many simultaneous information transmission have been developed, this is, to the best of our knowledge, one of the first quantum protocols to facilitate many-to-many simultaneous information exchange. Second, it guarantees complete anonymity and untraceability for all senders, a critical improvement over sequential applications of one-to-many protocols, which fail to ensure such robust anonymity. Third, leveraging quantum entanglement, the protocol operates in a fully distributed manner, accommodating brokers in diverse spatial locations. This approach marks a substantial advancement in secure, scalable, and anonymous communication, with potential applications in distributed environments where privacy and parallelism are paramount.
We present a quantum scheme for signing contracts between two clients (Alice and Bob) using entangled states and the services of a third trusted party (Trent). The trusted party is only contacted for the initialization of the protocol, and possibly at the end, to verify clients’ honesty and deliver signed certificates. The protocol is fair, i.e., the probability that a client, say Bob, can obtain a signed copy of the contract, while Alice cannot, can be made arbitrarily small, and scales as N − 1 / 2 , where 4 N is the total number of rounds (communications between the two clients) of the protocol. Thus, the protocol is optimistic, as cheating is not successful, and the clients rarely have to contact Trent to confirm their honesty by delivering the actual signed certificates of the contract. Unlike the previous protocol (Paunković et al., Phys. Rev. A 84, 062331 (2011)), in the present proposal, a single client can obtain the signed contract alone, without the need for the other client’s presence. When first contacting Trent, the clients do not have to agree upon a definitive contract. Moreover, even upon terminating the protocol, the clients do not reveal the actual contract to Trent. Finally, the protocol is based on the laws of physics, rather than on mathematical conjectures and the exchange of a large number of signed authenticated messages during the actual contract signing process. Therefore, it is abuse-free, as Alice and Bob cannot prove they are involved in the contract signing process.
A quantum internet is one of the promises of the second quantum revolution. New difficulties arise when the first quantum network (QN) hardware prototypes get closer to completion. The development of scalable QN systems is still in its early stages, yet a functioning network is more than simply the physical tools. The proposed method offers a QN protocol that addresses the novel conceptual and technological difficulties posed by quantum physics and enables end-to-end quantum communication. As the key procedure in quantum information science, quantum entanglement swapping (QES) has the potential to revolutionise QN communication. The suggested paradigm, which considers entanglement, enables safe communication utilising a trusted third party across a long-distance QN. The protocols might act as the basic structure of a future quantum internet. Even if scaling and entanglement coherence issues must be overcome, this research provides the groundwork for improving error-correcting codes and fault-tolerant quantum computers.