Multi-user semi-quantum privacy query method irrelevant to measurement equipment

Abstract

The invention relates to a multi-user semi-quantum privacy query method irrelevant to measurement equipment, and belongs to the field of quantum communication and information security. By introducing a quantum key distribution technology irrelevant to measurement equipment and semi-quantum operation, the complexity of the user equipment is remarkably reduced, and the system security is improved. According to the method, a semi-trusted third party is used for being responsible for product state preparation and Bell measurement, random operation of multiple users is combined, and the function that the multiple users inquire different data items at the same time under privacy protection is achieved. The method comprises the key steps of system initialization, quantum state preparation, Bell measurement, eavesdropping detection, key derivation and data encryption and decryption. According to the invention, while the privacy of the user and the security of the database are ensured, the capability requirement of the user is reduced, the side channel attack is resisted, and the usability and security of the protocol are improved.

Description

Technical Field

[0001] The invention belongs to the field of quantum communication and quantum information, and is a multi-user semi-quantum privacy query method that is independent of measurement equipment. Background Art

[0002] With the rapid development of quantum communication technology, privacy protection schemes based on the principles of quantum mechanics can theoretically provide unconditional security. However, existing quantum privacy query (QPQ) protocols still face several challenges in practical applications. For example, full quantum users need to have complex quantum measurement equipment and operation capabilities, which limits the widespread promotion of this technology among ordinary users. To this end, the concept of Semi-Quantum Private Query (SQPQ) came into being, which reduces the requirements for user devices by allowing some users to perform only classical operations and simple quantum operations (such as reflection or random selection), thereby improving practical feasibility.

[0003] On the other hand, traditional privacy query protocols are usually based on the trusted device assumption, assuming that all quantum devices work as designed. However, quantum devices are inevitably affected by manufacturing defects and environmental noise, which allows attackers to conduct side-channel attacks or device attacks through vulnerabilities, thereby threatening the security of the protocol. To solve this problem, measurement-device-independent (MDI) quantum communication protocols have become a research hotspot. The MDI protocol significantly improves the security of the system by eliminating the need to trust the measurement device.

[0004] At present, although some studies have explored the combination of MDI technology and semi-quantum protocols, they are mainly focused on single-user scenarios and lack systematic research on privacy query scenarios involving multiple users. In practical applications, such as medical data query, financial data analysis, and e-government, privacy queries often involve the interactive needs of multiple users, and existing solutions are difficult to effectively meet such needs.

[0005] In summary, how to design a semi-quantum privacy query method that supports multi-user participation and has measurement device-independent characteristics has become a key issue that needs to be solved in the field of quantum communication and privacy protection. This method should take into account the ease of use of user devices and the scalability of the protocol while ensuring system security and privacy, thereby promoting the actual implementation of quantum privacy protection technology. Summary of the invention

[0006] To solve the above technical problems, the present invention proposes a measurement device-independent multi-user semi-quantum private query method, and the specific steps of the method are as follows:

[0007] S1: Initialize the system and construct a key encoding rule;

[0008] S2: The semi-trusted third party prepares a product state sequence and distributes it to multiple users;

[0009] S3: Multiple users randomly select one of two semi-quantum operations to apply to the received particles to form a new state sequence and send the new state sequence to the semi-trusted third party;

[0010] S4: The database holder randomly prepares multiple BB84 state sequences and sends them to the semi-trusted third party;

[0011] S5: The semi-trusted third party performs Bell measurements on the received state sequences and announces all Bell measurement events, where the Bell measurement events include whether the Bell measurement is successful and the corresponding measurement results;

[0012] S6: The semi-trusted third party randomly selects half of the measurement positions as eavesdropping detection positions. The database holder and multiple users simultaneously announce the quantum states at the corresponding positions and calculate the error rate based on the measurement results. If the error rate is higher than the threshold, return to step S1; otherwise, continue;

[0013] S7: The database holder announces the bit values corresponding to the remaining measurement positions as required. Multiple users deduce the initial key based on their random operations, the bit values announced by the database holder, and the Bell measurement results at the corresponding positions;

[0014] S8: The database holder and multiple users process the initial key to obtain the encryption key and the decryption key. The database holder encrypts the entire database with the encryption key and sends it to multiple users, and multiple users decrypt it according to their respective decryption keys to complete the data query.

[0015] Advantages of the present invention:

[0016] The present invention proposes a measurement device-independent multi-user semi-quantum private query method. This method can be immune to side-channel attacks on the detection end, uses the idea of semi-quantum keys to reduce the quantum ability requirements of users, and uses Bell measurements by the semi-trusted third party to realize simultaneous retrieval of different data items by multiple users while ensuring the privacy of multiple users and the database, improving the practicability of quantum private query. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the measurement device-independent multi-user semi-quantum private query method provided by the present invention;

[0018] Figure 2 Schematic flowchart of an embodiment of the method for measurement device-independent multi-user semi-quantum private query provided by the present invention; Specific implementation manner

[0019] The following combines the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] A specific implementation manner of a method for measurement device-independent multi-user semi-quantum private query, the method is as follows: construct a measurement device-independent multi-user semi-quantum private query system, and the system structure diagram is as Figure 1 shown, including a semi-trusted third party Charlie, a database holder Bob, and multiple users {u 1 , u 2 ,..., u n} that only require semi-quantum capabilities, where n represents the number of users; among them, the semi-trusted third party is responsible for the preparation of product states, Bell measurement, and assisting the database and users to complete eavesdropping detection, the database holder is responsible for preparing the BB84 state sequence and providing data, and multiple users only need to have semi-quantum capabilities, and they are responsible for applying for data from the database.

[0021] Charlie is a semi-trusted third party, that is, he will honestly execute the steps of the method, but will try to obtain more user privacy and database information from the existing information as much as possible.

[0022] As Figure 2 shown, in one embodiment, a method for measurement device-independent multi-user semi-quantum private query includes:

[0023] S1: In the process of initializing the system, the database holder Bob, n query users u i (i = 1,..., n) and the semi-trusted third party Charlie negotiate the transmission error rate τ. Bob and n users negotiate the corresponding key encoding rules:

[0024]

[0025] S2: The semi-trusted third party Charlie prepares a product state sequence of length , where N represents the database size, k is a security parameter, c is a constant coefficient representing the probability of successful Bell measurement, and the product states in the sequence are from Randomly select from; and select the qubits at the corresponding positions from the product state sequence and send them to the users at the corresponding positions. After the sending is completed, announce the quantum states corresponding to the qubits.

[0026] S3: User u i (i = 1,..., n) Randomly select one of two semi-quantum operations for each received particle and apply it to the particle, which will form a new state sequence, and send the new state sequence to Charlie. The two semi-quantum operations are as follows:

[0027] CTRL: Return the qubit sent by Charlie without any operation to Charlie;

[0028] SIFT: After receiving the qubit, randomly select one from {|0>, |1>} with equal probability to prepare a new qubit and send it to Charlie.

[0029] S4: Bob randomly prepares n BB84 state sequences and sends them to Charlie, where each state in the sequence is randomly selected from {|0>, |1>, |+>, |->}.

[0030] S5: Charlie performs Bell measurement on the received corresponding state sequences and announces all Bell measurement events. Each Bell measurement event corresponding to a pair of sequences includes a position string P i of successful Bell measurement positions and an encoded string R i corresponding to the measurement results, where each element in the position string is a single-bit value, 0 represents a failed measurement event, and 1 represents a successful measurement event; the elements in the measurement result string are two-bit values {00, 01, 10, 11}, which respectively represent the results of Bell measurement {|φ + >, |φ - >, |ψ + >, |ψ - >}.

[0031] S6: Charlie randomly selects half of the measurement events according to the measurement results for eavesdropping detection. Bob and multiple users simultaneously announce the quantum states corresponding to the detection positions and calculate the error rate according to the measurement results to complete the eavesdropping detection;

[0032] The specific process of performing eavesdropping detection includes: setting an error rate threshold τ, taking Bob and u i as entities A and B respectively; obtaining the number e of particles in the sequence to be eavesdropping detected iEntity A and Entity B respectively compare the measurement results announced by Charlie based on the initial particle information and the selected random operations, and calculate the error rate of the sequence according to the number e of particles in the sequence to be wiretapped-detected. If the error rate is higher than the threshold τ, return to step S1; otherwise, continue the detection until the detection of the particles at the detection positions is completed. i Calculate the error rate of the sequence. If the error rate is higher than the threshold τ, return to step S1; otherwise, continue the detection until the detection of the particles at the detection positions is completed.

[0033] S7: Bob announces a bit string corresponding to the remaining measurement positions according to the rules. The rules for each bit value in the string are as follows:

[0034]

[0035] Among them, the left side of the rule is the initial state sent by Bob to Charlie, and the right side of the rule is the announced bit value. Multiple users deduce the initial key based on their selected random operations, the bit values announced by Bob, and the Bell measurement results at the corresponding positions. As shown in Table 1, the table lists the specific key deduction rules under four Bell measurement results.

[0036] Assume that the Bell measurement result is |φ + >. If the bit value announced by Bob is 0 and the random operation of the user is SIFT, then the user can deduce a definite result at this time. If the state prepared by the user's SIFT operation is |0> (|1>), then the user can deduce the initial key 0 (1); if the bit value announced by Bob is 0 and the random operation of the user is CTRL, then the user cannot deduce a definite result at this time; the analysis processes in the two cases when Bob announces the bit value 1 are similar; the analysis processes corresponding to the remaining three Bell measurement results are similar to the case where the measurement result is |φ + >.

[0037] Table 1 Initial key deduction rules

[0038]

[0039] S8: After S7, Bob and n users respectively share an initial asymmetric key. Bob and user u i(i = 1, ..., n) divides the initial key into λ groups, each group contains N-bit keys, and respectively obtains the encryption key and the decryption key through bitwise XOR; if multiple users obtain the decryption key, the scheme continues, if multiple users do not obtain the decryption key, the scheme restarts and returns to step S1; at this time, Bob obtains all the keys as the encryption key, and multiple users obtain a part of the keys as the decryption key. Suppose multiple users obtain the j-th bit key and the data to be retrieved is the i-th bit. At this time, multiple users send the shift s = j - i to the database holder. Bob shifts the encryption key and encrypts the entire database using the shifted encryption key and sends it to multiple users. Multiple users use the decryption key to obtain the data at the i-th position, completing the data query.

Claims

1. A measurement device-independent multi-user semi-quantum privacy query method, characterized in that: The process of distributing quantum keys to query users and database holders using the measurement device-independent quantum key distribution method includes: S1: Initialize the system and build key encoding rules; S2: A semi-trusted third party prepares the product state sequence and distributes it to multiple users; S3: Multiple users randomly select one of the two semi-quantum operations and apply it to the received particles to form a new state sequence and send the new state sequence to a semi-trusted third party; S4: The database holder randomly prepares multiple BB84 state sequences and sends them to a semi-trusted third party; S5: The semi-trusted third party performs Bell measurement on the received state sequence and publishes all Bell measurement events. The Bell measurement events include whether the Bell measurement is successful or not and the corresponding measurement results. S6: The semi-trusted third party randomly selects half of the measurement positions as eavesdropping detection positions. The database holder and multiple users simultaneously publish the quantum states of the corresponding positions and calculate the error rate based on the measurement results. If the error rate is higher than the threshold, return to step S1, otherwise continue; S7: The database holder publishes the bit values ​​corresponding to the remaining measurement positions as required, and multiple users derive the initial key based on their own random operations, the bit values ​​published by the database holder, and the Bell measurement results of the corresponding positions; S8: The database holder and multiple users process the initial key to obtain an encryption key and a decryption key. The database holder encrypts the entire database with the encryption key and sends it to multiple users. Multiple users decrypt the database according to their respective decryption keys to complete data query.

2. According to the measurement device-independent multi-user semi-quantum privacy query method of claim 1, it is characterized in that: The initialization system process includes: S11: Database holder, multiple users and semi-trusted third party determine the error rate τ; S12: The database owner and multiple users determine the security parameter k and encoding rules.

3. The measurement device-independent multi-user semi-quantum privacy query method according to claim 2, characterized in that: The key encoding rules include: Bob and n query users u i (i=1,...,n) negotiate the corresponding key encoding rule, and the basic principle of encoding is to encode two groups of non-orthogonal states into 0 and 1 respectively.

4. The measurement device-independent multi-user semi-quantum privacy query method according to claim 2, characterized in that: In step S2, the semi-trusted third party Charlie prepares An initial product state is generated, and the qubits at corresponding positions are selected from the product state and sent to the corresponding query users. During the transmission process, the lost particles are ignored and retransmitted until Duoyong and announce that all particles have been received. After the transmission is completed, Charlie announces the quantum state corresponding to the qubit.

5. The measurement device-independent multi-user semi-quantum privacy query method according to claim 2, characterized in that: In step S3, the user randomly selects a half-quantum operation for each received particle, applies it to the particle, and returns it to Charlie. After each user's random half-quantum operation, a new qubit sequence will be obtained, and these new sequences are received by Charlie.

6. The measurement device-independent multi-user semi-quantum privacy query method according to claim 2, characterized in that: In step S4, Bob prepares a sequence of n BB84 states and sends them to Charlie, where each state in the sequence is randomly selected from {|0>,|1>,|+>,|->}.

7. The measurement device-independent multi-user semi-quantum privacy query method according to claim 2, characterized in that: In step S5, Charlie performs Bell measurement on the received state sequence and publishes all measurement events, where the measurement event includes a position string P of a successful Bell measurement. i and the corresponding measurement result code string R i .

8. The measurement device-independent multi-user semi-quantum privacy query method according to claim 2, characterized in that: The process of eavesdropping detection in step S6 includes: Charlie randomly selects half of the measurement positions as eavesdropping detection positions according to the measurement results, and Bob and u i The number of particles contained in the detection position is obtained, and the measurement results are compared according to the initial particle information and the selected random operation. Then, the error rate is calculated according to the comparison result and the number of particles and compared with the error rate threshold τ. If the error rate is higher than the threshold, the detection is terminated and the protocol process is restarted. Otherwise, the detection is continued until all particles are detected.

9. The measurement device-independent multi-user semi-quantum privacy query method according to claim 2, characterized in that: Step S7 includes Bob publishing the bit values ​​at the remaining measurement positions according to the rules, and the user derives the initial key according to the operation selected by the user, the bit value published by Bob and the measurement result of the position.

10. The measurement device-independent multi-user semi-quantum privacy query method according to claim 2, characterized in that: In step S8, Bob and n users share an initial asymmetric key. i (i=1,...,n) The initial key is divided into λ groups, each group contains N-bit keys, and the encryption key and decryption key are obtained by bitwise XOR; if multiple users obtain the decryption key, the scheme continues, if multiple users do not obtain the decryption key, the scheme restarts and returns to step S1; at this time, Bob obtains all the keys as encryption keys, and multiple users obtain part of the keys as decryption keys. Assuming that multiple users obtain the j-th key, the i-th data to be retrieved is, at this time, the multiple users send the shift s=ji to the database holder, Bob shifts the encryption key, and uses the shifted encryption key to encrypt the entire database and send it to multiple users, and the multiple users use the decryption key to obtain the data at the i-th position.

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