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.
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.
This paper introduces two information-theoretically quantum secure direct communication protocols that accomplish information exchange between Alice and Bob in the first case, and among Alice, Bob, and Charlie in the second case. Both protocols use a novel method, different from existing similar protocols, to embed the secret information in the entangled compound system. This new way of encoding the secret information is one of the main novelties of this paper, and a distinguishing feature compared to previous works in this field. A second critical advantage of our method is its scalability and extensibility because it can be seamlessly generalized to a setting involving three, or more, players, as demonstrated by the second protocol. This trait is extremely beneficial in many real-life situations, where many spatially separated players posses only part the secret information that must be transmitted to Alice, so that she may obtain the complete secret. Using the three-player protocol, this task can be achieved in one go, without the need to apply a typical QSDC protocol twice, where Alice first receives Bob’s and then Charlie’s information. The proposed protocol does not require pre-shared keys or quantum signatures, making it less complicated and more straightforward. Finally, in anticipation of the coming era of distributed quantum computing, our protocols offer the important practical advantage of straightforward implementation on contemporary quantum computers, as they only require standard CNOT and Hadamard gates.
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.
We propose a simultaneous quantum secure direct communication scheme between one party and other three parties via four-particle GHZ states and swapping quantum entanglement. In the scheme, three spatially separated senders, Alice, Bob and Charlie, transmit their secret messages to a remote receiver Diana by performing a series of local operations on their respective particles according to the quadripartite stipulation. From Alice, Bob, Charlie and Diana's Bell measurement results, Diana can infer the secret messages. If a perfect quantum channel is used, the secret messages are faithfully transmitted from Alice, Bob and Charlie to Diana via initially shared pairs of four-particle GHZ states without revealing any information to a potential eavesdropper. As there is no transmission of the qubits carrying the secret message in the public channel, it is completely secure for the direct secret communication. This scheme can be considered as a network of communication parties where each party wants to communicate secretly with a central party or server.
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 give an example of a wide class of problems for which quantum-information protocols based on multisystem entanglement can be mapped into much simpler ones involving one system. Secret sharing is a cryptographic primitive which plays a central role in various secure multiparty computation tasks and management of keys in cryptography. In secret sharing protocols, a classical message is divided into shares given to recipient parties in such a way that some number of parties need to collaborate in order to reconstruct the message. Quantum protocols for the task commonly rely on multipartite GHZ entanglement. We present a multiparty secret sharing protocol which requires only sequential communication of a single quantum d-level system (for any prime d). It has huge advantages in scalability and can be realized with state-of-the-art technology.
This paper introduces the Symmetric Extensible Quantum Secret Sharing protocol, a novel quantum protocol for secret sharing. At its heart, it is an entanglement-based protocol that relies on the use of maximally entangled GHZ tuples, evenly distributed among the players, endowing the spymaster with the ability to securely share a secret message with the agents. Its security stems from the fact that it is highly improbable for a malicious eavesdropper or a rogue double agent to disrupt its successful execution. It is characterized by symmetry, since all agents are treated indiscriminately, utilizing identical quantum circuits. Furthermore, it can be seamlessly extended to an arbitrary number of agents. Finally, after the completion of the quantum part of the protocol, the spymaster will have to publicly transmit some information, in order to allow the agents to unlock the secret message. This part of the protocol can be considered as an additional advantage, due to the fact that it gives the spymaster the privilege of deciding if, or when, it is the right time for the agents to unlock the secret message, after the completion of the quantum part of the protocol.