Loss-tolerant measurement-device-independent quantum private queries

Abstract

Quantum private queries (QPQ) is an important cryptography protocol aiming to protect both the user’s and database’s privacy when the database is queried privately. Recently, a variety of practical QPQ protocols based on quantum key distribution (QKD) have been proposed. However, for QKD-based QPQ the user’s imperfect detectors can be subjected to some detector- side-channel attacks launched by the dishonest owner of the database. Here, we present a simple example that shows how the detector-blinding attack can damage the security of QKD-based QPQ completely. To remove all the known and unknown detector side channels, we propose a solution of measurement-device-independent QPQ (MDI-QPQ) with single- photon sources. The security of the proposed protocol has been analyzed under some typical attacks. Moreover, we prove that its security is completely loss independent. The results show that practical QPQ will remain the same degree of privacy as before even with seriously uncharacterized detectors.

Efficient quantum private queries based on quantum key distribution with pulse-position modulation

“…Moreover, we assume that the quantum channel is noiseless so Alice receives the quantum states correctly every time. Similar to QPQ protocols [1,2,[4][5][6][7][8][9][10], in our QPQ protocol, the indistinguishability of nonorthogonal quantum states also guarantee the privacy of the database. In other words, Alice announces which states have been projected to Bell her about the classical information of his transmitted states.…”

“…As analyzed in Zhao et al's protocols [2], Alice can increase the probability p of the raw key by storing the received photons in QMs and performing the unambiguous state discrimination (USD) measurements after step (3). The successful probability of the USD, for Bob's announced two honest states,…”

“…Compared with the existing QPQ protocols [1][2][3][4][5][6][7][8][9][10], our protocol has certain merits. For example, it is much more flexible for practical application, and greatly saves both quant um and classical communication.…”

“…B 1 is composed of two ground states of the orbital angular momentum, which are orthogonal to each other and are rotationally invariant. It is because of this rotation invariance that our protocol solves the basis dependency problem which exists in QPQ protocols [1][2][3][4][5][6][7][8][9][10] generated by the use of polarization coding or phase coding. On the other hand, B 2 does not have rotation invariance, so, we use it to correct the error, and the mismatch error probability of the base is zero.…”

“…They call this requirement 'user privacy'. Recently, many improved QPQ protocols [2][3][4][5][6][7][8][9][10] have been proposed. Similar to the BB84 quantum key distribution (QKD) protocol [11], most QPQ solutions use weak coherent pulses (WCPs) as an ideal single-photon source, which is technically infeasible.…”