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Quantum Private Queries: Security Analysis

Vittorio Giovannetti, Seth Lloyd, Lorenzo Maccone

Published Aug 1, 2009• 51 citations
OpenAlex

Abstract

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.

Related papers

Quantum Private Queries: Security Analysis

Vittorio Giovannetti, Seth Lloyd, Lorenzo Maccone

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.

arXiv:0809.1934•IEEE Transactions on Information Theory•Jun 23, 2010•83 citations

Quantum Private Queries

Vittorio Giovannetti, Seth Lloyd, Lorenzo Maccone

We propose a cheat sensitive quantum protocol to perform a private search on a classical database which is efficient in terms of communication complexity. It allows a user to retrieve an item from the database provider without revealing which item he or she retrieved: if the provider tries to obtain information on the query, the person querying the database can find it out. The protocol ensures also perfect data privacy of the database: the information that the user can retrieve in a single query is bounded and does not depend on the size of the database. With respect to the known (quantum and classical) strategies for private information retrieval, our protocol displays an exponential reduction in communication complexity and in running-time computational complexity.

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Reexamination of the realtime protection for user privacy in practical quantum private query

Chun‐Yan Wei, Xiao‐Qiu Cai, Tian‐Yin Wang

Abstract Quantum private query (QPQ) is the quantum version for symmetrically private information retrieval. However, the user privacy in QPQ is generally guarded in the delayed and cheat-sensitive way. That is, the dishonest database holder Bob’s cheating to elicit user privacy can only be discovered after the protocol is finished (when the user finds some errors in the retrieved database item). Such delayed detection may cause very unpleasant results for the user Alice in real-life applications. Without the realtime conscious of privacy leaking, Alice may make faulty decisions according to the received faulty item and suffer great loss. Worse yet, it is difficult for Alice to accuse a dishonest database to any one else though she can detect the cheating. Current efforts to protect user privacy in realtime in existing QPQ protocols mainly use two techniques, i.e. adding an honesty checking on the database or allowing the user to reorder the qubits. We reexamine these two kinds of QPQ protocols and find neither of them can work very well. We give concrete cheating strategies for both participants and show that honesty checking of inner participant should be dealt more carefully in for example the choosing of checking qubits. Finally, we give an idea to realize realtime detection of dishonest database in QPQ of blocks (i.e. multi-bit database items).

arXiv:2407.19147•Physica Scripta•Nov 18, 2024•1 citation

A Quantum Private Query Protocol for Enhancing both User and Database Privacy*

Yi‐Hua Zhou, Xuewei Bai, Lei-Lei Li +2 more

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.

Communications in Theoretical Physics•Jan 1, 2018•8 citations

Impossibility of quantum private queries

Esther Hänggi, Severin Winkler

Symmetric private information retrieval is a cryptographic task allowing a user to query a database and obtain exactly one entry without revealing to the owner of the database which element was accessed. The task is a variant of general two-party protocols called and is closely related to oblivious transfer. Under the name , quantum protocols have been proposed to solve this problem in a cheat-sensitive way: In such protocols, it is not impossible for dishonest participants to cheat, but they risk detection [Giovannetti , ]. We give an explicit attack against any cheat-sensitive symmetric private information retrieval protocol, showing that any protocol that is secure for the user cannot have nontrivial security guarantees for the owner of the database: The user is even able to retrieve the database.

arXiv:2501.12842•Physical Review Research•Apr 3, 2026•0 citations

Improving User Privacy in Practical Quantum Private Query with Group Honesty Checking

Chun‐Yan Wei, Qingle Wang, Xiao‐Qiu Cai +1 more

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).

Advanced Quantum Technologies•Feb 12, 2025•4 citations
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.
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.
We propose a cheat sensitive quantum protocol to perform a private search on a classical database which is efficient in terms of communication complexity. It allows a user to retrieve an item from the database provider without revealing which item he or she retrieved: if the provider tries to obtain information on the query, the person querying the database can find it out. The protocol ensures also perfect data privacy of the database: the information that the user can retrieve in a single query is bounded and does not depend on the size of the database. With respect to the known (quantum and classical) strategies for private information retrieval, our protocol displays an exponential reduction in communication complexity and in running-time computational complexity.
Abstract Quantum private query (QPQ) is the quantum version for symmetrically private information retrieval. However, the user privacy in QPQ is generally guarded in the delayed and cheat-sensitive way. That is, the dishonest database holder Bob’s cheating to elicit user privacy can only be discovered after the protocol is finished (when the user finds some errors in the retrieved database item). Such delayed detection may cause very unpleasant results for the user Alice in real-life applications. Without the realtime conscious of privacy leaking, Alice may make faulty decisions according to the received faulty item and suffer great loss. Worse yet, it is difficult for Alice to accuse a dishonest database to any one else though she can detect the cheating. Current efforts to protect user privacy in realtime in existing QPQ protocols mainly use two techniques, i.e. adding an honesty checking on the database or allowing the user to reorder the qubits. We reexamine these two kinds of QPQ protocols and find neither of them can work very well. We give concrete cheating strategies for both participants and show that honesty checking of inner participant should be dealt more carefully in for example the choosing of checking qubits. Finally, we give an idea to realize realtime detection of dishonest database in QPQ of blocks (i.e. multi-bit database items).
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.
Symmetric private information retrieval is a cryptographic task allowing a user to query a database and obtain exactly one entry without revealing to the owner of the database which element was accessed. The task is a variant of general two-party protocols called and is closely related to oblivious transfer. Under the name , quantum protocols have been proposed to solve this problem in a cheat-sensitive way: In such protocols, it is not impossible for dishonest participants to cheat, but they risk detection [Giovannetti , ]. We give an explicit attack against any cheat-sensitive symmetric private information retrieval protocol, showing that any protocol that is secure for the user cannot have nontrivial security guarantees for the owner of the database: The user is even able to retrieve the database.
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).