Quantum private query (QPQ) requires that the database holder Bob knows nothing about his client Alice, including the $index$ she provides and the $element$ she obtains. However, on some occasion,… Click to show full abstract
Quantum private query (QPQ) requires that the database holder Bob knows nothing about his client Alice, including the $index$ she provides and the $element$ she obtains. However, on some occasion, Bob wants to know which $element$ he has revealed to Alice. Therefore, we raise a symmetric quantum private query (SQPQ) problem in this paper. SQPQ can guarantee that Alice shares the real $element$ with Bob and also partially protect the privacy of Alice’s $index$ . Some necessary conditions are need to satisfy to implement SQPQ. We prove that Alice must provide some extra information to enable Bob to know the $element$ . Then, we define the term “absolutely secure”, which is a security notion stronger than cheat sensitive, and prove that “absolutely secure” SQPQ is impossible. In addition, we raise a cheat sensitive scheme three-databases-detection to implement SQPQ protocol. Finally, we construct a reduction from SQPQ to quantum bit commitment (QBC) to clarify that SQPQ is a problem more difficult than QBC.
