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IEEE Journal on Selected Areas in Communications

Error Tolerance Bound in QKD-Based Quantum Private Query

Chun‐Yan Wei, Xiao‐Qiu Cai, Tian‐Yin Wang, Su‐Juan Qin, Fei Gao, Qiaoyan Wen

Published Jan 23, 2020• 60 citations
Publisher

Abstract

Most existing quantum private query (QPQ) protocols can hardly work in the presence of noise. The user Alice may obtain a false database item in noisy environments and both participants may cheat under the disguise of noise, so dealing with the noise needs an overall consideration of error correction, user privacy and database security. However, the only two existing protocols aiming to correct errors in QPQ lack such an overall consideration (at least one party's privacy can be revealed), and they did not estimate what extent of errors can be tolerated (actually, noise is seldom discussed in quantum two-party secure computations, and to the best of our knowledge, relevant bounds on tolerable errors remain unattainable so far). To solve this problem, we first exemplify how one participant reveals the other party's privacy in the existing QPQ protocols aiming to correct errors. Then we propose a practical protocol which can really work via noisy channel, that is, the error rate of the retrieved database item is reduced significantly and both parties' privacy are well protected. Besides, we deduce that the final error rate, user privacy and database security are pairwise in a “trade-off” relationship. By balancing them according to the required level of security and reliability, we obtain an upper bound on tolerable errors.

DOI
10.1109/jsac.2020.2968998

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Most existing quantum private query (QPQ) protocols can hardly work in the presence of noise. The user Alice may obtain a false database item in noisy environments and both participants may cheat under the disguise of noise, so dealing with the noise needs an overall consideration of error correction, user privacy and database security. However, the only two existing protocols aiming to correct errors in QPQ lack such an overall consideration (at least one party's privacy can be revealed), and they did not estimate what extent of errors can be tolerated (actually, noise is seldom discussed in quantum two-party secure computations, and to the best of our knowledge, relevant bounds on tolerable errors remain unattainable so far). To solve this problem, we first exemplify how one participant reveals the other party's privacy in the existing QPQ protocols aiming to correct errors. Then we propose a practical protocol which can really work via noisy channel, that is, the error rate of the retrieved database item is reduced significantly and both parties' privacy are well protected. Besides, we deduce that the final error rate, user privacy and database security are pairwise in a “trade-off” relationship. By balancing them according to the required level of security and reliability, we obtain an upper bound on tolerable errors.
Quantum private query (QPQ) faces many challenges in practical applications. At present, some scholars have made substantial work on overcoming channel loss, channel noise, and nonideal light sources, respectively. However, a protocol that would overcome all three of these problems has yet to materialize. We review a practical QPQ protocol that can actually work in noisy channels. This protocol has an upper bound on tolerable errors based on the required level of security and reliability. Then, we study the security of the above QPQ protocol under weak coherent pulses. The results indicate that the multiphoton pulses have induced significant vulnerabilities, which seriously threatens the privacy of users. Finally, we propose a decoy-state method to solve the serious threat to user security caused by multiphoton pulses. The analysis shows that the decoy-state method significantly improves the security of the QPQ protocol under weak coherent pulses. The improved protocol can not only tolerate transmission losses and channel noise, but also overcome the security vulnerability caused by a nonideal light source.
Quantum Private Information Retrieval (QPIR) allows a user (Alice) to retrieve a database item from the database owned by the database holder (Bob) in such a way that Alice can query only the database item she wants, but cannot get other items, and Bob does not know which item Alice queries. However, the real quantum channel between Alice and Bob is noisy, and the noise may result in not only the chance that Alice obtains a false item, but also that both parties may cheat by camouflaging themselves with noise. In this paper, we use the decoherence-free subspace (DFS) for QPIR, which we call DFS-QPIR. The DFS-QPIR protocol removes the effect of the channel noise on the errors in the retrieved item so that two parties cannot cheat by replacing the noisy channel with a noiseless one. It can work over a collective noisy channel while retaining high reliability, database security and user privacy simultaneously. While only the collective unitary noise is taken into account, the proposed DFS-QPIR protocol can be straightforwardly extended to more general collective noise channel.
A security analysis of the recently introduced Quantum Private Query (QPQ) protocol is presented. The latter is a cheat sensitive quantum protocol to perform a private search on a classical database. It allows a user to retrieve an item from the database without revealing which item was retrieved, and at the same time it ensures data privacy of the database (the information that the user retrieves in a query is bounded). The security analysis is based on information-disturbance tradeoffs which show that whenever the provider tries to obtain information on the query, the query (encoded into a quantum system) is disturbed so that the person querying the database can detect the privacy violation. The security bounds are derived under the assumption that a unique answer corresponds to each query. To remove this assumption, some simple variants of the protocol are illustrated, and it is conjectured that analogous security bounds apply to them.
Abstract Current cheat‐sensitive security level of user privacy in quantum private query (QPQ) is far from meeting its ideal requirement. Dishonest database trying to elicit user privacy can only be (delayedly) detected after the finish of the protocol with merely a nonzero probability. Worse yet, no estimation of (i.e., the success probability of dishonest database's cheating) has been given till now. Such estimation is quite necessary because a significant means frangible user privacy especially in the cheat‐sensitive security model. Here, of the first and best‐known quantum‐key‐distribution (QKD)‐based QPQ protocol proposed by Jakobi et al. is estimated, which shows that dishonest database can elicit user privacy with significant probability (e.g., as high as 42.8% for database size ) while such cheating can only be (delayedly) detected with probability 50 %. Common strategy to improve user privacy, i.e., adding honesty checking to detect malicious database may hurt the privacy of the other party, i.e. database security. To solve this problem, a new group honesty checking is proposed, which will not hurt database security and can reduce $ to a very small value (e.g. 0.26% for database size 10000), thus assuring high user privacy (note that = 0 means ideal user privacy).
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.
A security analysis of the recently introduced Quantum Private Query (QPQ) protocol is presented. The latter is a cheat sensitive quantum protocol to perform a private search on a classical database. It allows a user to retrieve an item from the database without revealing which item was retrieved, and at the same time it ensures data privacy of the database (the information that the user retrieves in a query is bounded). The security analysis is based on information-disturbance tradeoffs which show that whenever the provider tries to obtain information on the query, the query (encoded into a quantum system) is disturbed so that the person querying the database can detect the privacy violation. The security bounds are derived under the assumption that a unique answer corresponds to each query. To remove this assumption, some simple variants of the protocol are illustrated, and it is conjectured that analogous security bounds apply to them.