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Physical Review A

Private database queries based on counterfactual quantum key distribution

Jia-Li Zhang, Fen-Zhuo Guo, Fei Gao, Bin Liu, Qiaoyan Wen

Published Aug 27, 2013• 94 citations
Publisher

Abstract

Based on the fundamental concept of quantum counterfactuality, we propose a protocol to achieve quantum private database queries, which is a theoretical study of how counterfactuality can be employed beyond counterfactual quantum key distribution (QKD). By adding crucial detecting apparatus to the device of QKD, the privacy of both the distrustful user and the database owner can be guaranteed. Furthermore, the proposed private-database-query protocol makes full use of the low efficiency in the counterfactual QKD, and by adjusting the relevant parameters, the protocol obtains excellent flexibility and extensibility.

DOI
10.1103/physreva.88.022334

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Based on the fundamental concept of quantum counterfactuality, we propose a protocol to achieve quantum private database queries, which is a theoretical study of how counterfactuality can be employed beyond counterfactual quantum key distribution (QKD). By adding crucial detecting apparatus to the device of QKD, the privacy of both the distrustful user and the database owner can be guaranteed. Furthermore, the proposed private-database-query protocol makes full use of the low efficiency in the counterfactual QKD, and by adjusting the relevant parameters, the protocol obtains excellent flexibility and extensibility.
Abstract To save quantum resources and improve efficiency, this article proposes an efficient counterfactual quantum privacy query protocol. Counterfactual quantum privacy query refers to the identification of secure detection and key screening based on the detector's response results without the actual transmission of quantum information between user Bob and database Alice. Alice completes key transmission through a counterfactual device, while Bob measures the photon's polarization with a probability of 1/2 to obtain the encoded classical information, followed by traditional post-processing and privacy query operations. Additionally, to withstand the noise impact during the communication process, a modified counterfactual QKD protocol proposed by Rao (2021) is utilized, where communication parties randomly select a quantum bit flip with a specified probability \textit{f}, and then complete the quantum privacy query.
Quantum key distribution (QKD)-based quantum private query (QPQ) is a practical application of QKD, which relaxes the security condition of perfectly concealing a private query to a cheating-sensitive strategy. We propose a QPQ protocol based on the delegated QKD scheme (DQKD-based QPQ), in which two almost 'classical' clients (data user and database owner) can establish a 1-out-of-N oblivious key with the help of a cloud server with full quantum ability. Concretely, the two classical participants in the DQKD-based QPQ only need to access the quantum channel and reorder qubits, and the costly quantum operations, quantum state preparation and measurement are outsourced to a full quantum server in the cloud without leaking participants' privacy. The proposed protocol not only provides a cloud-based framework of QKD-based QPQ, but also obtains better security by a real-time security check, which can protect the security of the database and user against all potential attacks even if the quantum server is assumed to be a powerfully untrusted adversary .
By adding a parameter θ in M. Jakobi et al's protocol [Phys. Rev. A 83, 022301 (2011)], we present a flexible quantum-key-distribution-based protocol for quantum private queries. We show that, by adjusting the value of θ, the average number of the key bits Alice obtains can be located on any fixed value the users wanted for any database size. And the parameter k is generally smaller (even k = 1 can be achieved) when θ < π/4, which implies lower complexity of both quantum and classical communications. Furthermore, the users can choose a smaller θ to get better database security, or a larger θ to obtain a lower probability with which Bob can correctly guess the address of Alice's query.
Abstract In order to protect the privacy of query user and database, some QKD-based quantum private query (QPQ) protocols were proposed. Unfortunately some of them cannot resist internal attack from database perfectly; some others can ensure better user privacy but require a reduction of database privacy. In this paper, a novel two-way QPQ protocol is proposed to ensure the privacy of both sides of communication. In our protocol, user makes initial quantum states and derives the key bit by comparing initial quantum state and outcome state returned from database by ctrl or shift mode instead of announcing two non-orthogonal qubits as others which may leak part secret information. In this way, not only the privacy of database be ensured but also user privacy is strengthened. Furthermore, our protocol can also realize the security of loss-tolerance, cheat-sensitive, and resisting JM attack etc.
Private queries allow a user, Alice, to learn an element of a database held by a provider, Bob, without revealing which element she is interested in, while limiting her information about the other elements. We propose to implement private queries based on a quantum-key-distribution protocol, with changes only in the classical postprocessing of the key. This approach makes our scheme both easy to implement and loss tolerant. While unconditionally secure private queries are known to be impossible, we argue that an interesting degree of security can be achieved by relying on fundamental physical principles instead of unverifiable security assumptions in order to protect both the user and the database. We think that the scope exists for such practical private queries to become another remarkable application of quantum information in the footsteps of quantum key distribution.
Symmetric private information retrieval (SPIR) protocol is proposed for users to retrieve items from a database holder without revealing the retrieval address, and meanwhile the users cannot learn any additional entries of the database. Quantum key distribution (QKD)-based quantum private queries (QPQs) are the most practical protocols for the SPIR problem. However, most existing protocols assume ideal devices. To overcome this drawback, we propose a device independent QPQ protocol based on QKD with imperfect sources and detectors. By constructing the semi-definite programming optimization problem, we give the CHSH test threshold and prove the correctness of our protocol. We use the shift and permutation post-processing technique to further improve the security. We compare the performance of our protocol with a recent full device-independent QPQ. and discuss their relative advantages. The simulation results show that our protocol improves database security, user privacy and efficiency. The number of final key bits that Alice knows is close to 1, and Bob’s guessing probability is below 0.15 in our protocol. Moreover, the proposed scheme can be used for any entanglement-based QPQ protocol to remove trust on the devices.