A location privacy protection method based on a cooperative service

Abstract

This invention relates to the field of software communication technology and discloses a location privacy protection method based on collaborative services. The method includes: S1, System Initialization: TA generates a system public key PK, a system private key MSK, a tracking key TK, and system parameters params; S2, User Registration: RU... i CU j RSU and LSP register with TA respectively, generating their respective public-private key pairs; S3, Service Query: RU i Generate location service query SQ i This location privacy protection method based on collaborative services provides users with location services with a higher level of security and achieves the following three goals: First, it uses a Bloom filter to build a secure index for users to provide secure location services; second, it ensures that users' location privacy is not disclosed when responding to RSUs; and finally, it ensures that when any two users are engaged in collaborative services, neither user can infer the other's location privacy from the content of the collaborative service.

Description

Technical Field

[0001] This invention relates to the field of software communication technology, specifically to a location privacy protection method based on collaborative services. Background Technology

[0002] The Internet of Vehicles (IoV) refers to the comprehensive network connectivity achieved through next-generation mobile communication technologies, enabling connections within vehicles, between vehicles and people, between vehicles themselves, between vehicles and roads, and between vehicles and service platforms. Its emergence has not only greatly facilitated people's transportation but also significantly aided government departments in establishing intelligent transportation systems, such as improving road safety and traffic efficiency. However, the "data fingerprints" generated during data interaction pose a privacy and security threat to users. Hackers can use data mining and other techniques to analyze collected user data and obtain sensitive user information.

[0003] To address the aforementioned issues, scholars have proposed privacy protection schemes for connected vehicles based on anonymity and cryptography. For attackers with certain knowledge, ordinary anonymity-based location privacy protection schemes are insufficient to protect user location privacy. Therefore, a double-anonymity-based location privacy protection scheme is proposed. This scheme introduces a trusted cloud service between the user and the location service provider to reduce the correlation between the user and service requests, thereby maximizing user location privacy protection. To improve the effectiveness, uncertainty, and dispersion of virtual locations under road constraints, and to avoid privacy and security issues arising from providing users' real location information, a location privacy protection algorithm based on virtual locations under road constraints is proposed, which does not require a trusted third-party server. The convenience of ride-sharing comes at the expense of driver and passenger privacy. Therefore, an anonymous mutual authentication protocol is proposed, in which drivers and passengers anonymously send ride-sharing queries to the cloud server to complete the ride-sharing service. To help drivers quickly and accurately find the required parking spaces, a privacy-preserving intelligent parking navigation scheme is proposed. In this scheme, after a user initiates a parking space query to the cloud server, the cloud server searches for and generates available parking locations that meet the user's expectations, which the user then retrieves. However, these solutions have limitations in terms of user privacy and resource consumption. On the one hand, anonymity-based solutions typically replace the user's real location information with an anonymous set for location-based services, but their communication overhead generally increases linearly with the size of the anonymous set. On the other hand, cryptographic solutions typically encrypt the location information and send it to the server, which then decrypts it to obtain the corresponding plaintext information before returning the location-based service. In this process, the user's privacy information is often leaked due to server system vulnerabilities or attacks from malicious adversaries.

[0004] Using location-based services typically requires users to submit their past, present, or future location information, which inevitably leads to the aforementioned problems. One existing research approach is based on distributed collaborative services. This approach allows requesting users to initiate location-based service requests in a privacy-preserving manner, and collaborating users can then respond with corresponding location services. While this process avoids disclosing any sensitive user information and effectively protects user privacy, it suffers from issues such as duplicate and wasted response resources. The main reason for this is its inability to filter out duplicate responses from collaborating users.

[0005] Bloom filters are space-efficient and fast-querying random data structures used to check if an element is in a set. Because they don't require storing the elements themselves, they also offer a degree of confidentiality regarding the elements. Furthermore, as a technique for performing equivalence tests in ciphertext, ciphertext equivalence testing is widely used to test whether the corresponding plaintext information of different ciphertexts is equal, thus enabling the determination of relationships between ciphertexts without requiring a decryption key.

[0006] As can be seen from the above, while existing privacy protection schemes for connected vehicles based on anonymity and cryptography can protect user privacy to a certain extent, they also have some shortcomings. For example... Figure 1 As shown, X preprocesses its location information using K-anonymity or cryptography and sends a service query to Y. Y then returns a corresponding service response to X based on the received service query. In this process, due to the inherent privacy and security risks and significant communication resource consumption, existing vehicle-to-everything (V2X) privacy protection solutions still face considerable challenges. Therefore, improvements are needed. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a location privacy protection method based on collaborative services. This method has the advantages of privacy security, low communication overhead, high efficiency of collaborative services, and repeatability verification based on ciphertext equivalence testing. It solves the privacy security risks and high communication resource consumption caused by location service queries initiated in a K-anonymous or cryptographic manner.

[0009] (II) Technical Solution

[0010] To achieve the aforementioned objectives of privacy and security, low communication overhead, high efficiency of collaborative services, and repeatability verification based on ciphertext equivalence testing, this invention provides the following technical solution:

[0011] A location privacy protection method based on collaborative services includes the following steps:

[0012] S1. System initialization: TA generates the system public key PK, system private key MSK, tracking key TK, and system parameters params;

[0013] S2, User Registration: RU i CU j RSU and LSP register with TA respectively, generating their own public-private key pairs;

[0014] S3, Service Inquiry: RU i Generate location service query sQ i And send it to the LSP via RSU;

[0015] S4. Query Verification: LSP receives RU i SQ sent i Next, its validity is verified. If the verification fails, the query is rejected; otherwise, the location service query SQ′ is executed. i Send to RSU;

[0016] S5, Proxy Service: The RSU receives the SQ′ sent by the LSP. i Then, a coordination signal CS is broadcast to the surrounding CUs. j and for RU i Perform proxy services, thereby communicating with CU j Data interaction is performed. During this process, CU... j Identity and collaboration verification must be performed with the RSU. For successfully verified CUs... j It generates a ciphertext O of a location service set S and sends it to RSU;

[0017] S6. Repeatability Test: RSU is conducted by RU i The test trapdoor ET sent through the secure channel is used to test n CUs. j The generated n location service ciphertexts O are subjected to repeatability testing. If the test passes, a location service response SR is generated. i，j And send it to the LSP for storage;

[0018] S7, Service Search: RU i A location service search trapdoor (ST) is sent to the LSP, and the LSP then returns the corresponding search results to the RU. i

[0019] S8. User Tracking: When a user engages in malicious behavior, their identity can be revealed through the tracking key TK.

[0020] Preferably, S1 has the following detailed description:

[0021] S1.1 Given a security parameter, the generation order of TA is a prime number p (p≥2). λ A cyclic group G of ), where g∈G is a generator;

[0022] S1.2 Given the security parameter δ, TA generates an invertible matrix. Vector V = {(v1, ..., v ...2, ..., v3, ..., v4, ..., v δ ) T |v i ∈ R {0, 1}}, hash key set Pseudo-random function F: {0,1} * ×{0, 1} δ →{0,1} * and l independent position-sensitive hash functions

[0023]

[0024] S1.3, TA generates three secure hash functions. H2: {0, 1} * →{0,1} 2ρ H3: {0, 1} * →{0,1} λ ;

[0025] S1.4, Number of TA selections calculate

[0026] S1.5, TA generates the system public key PK = (h1, h2, h3), the system private key MSK = (α, M1, M2, V), the tracking key TK = (ξ1, ξ2) and the system parameters params = (G, p, e, g, PK, H1, H2, H3, H, F), where TA publishes the system parameters params and keeps the system private key MSK and the tracking key TK private.

[0027] Preferably, step S2 has the following detailed description:

[0028] S2.1, Number of RU selections calculate And Send it to TA via a secure channel;

[0029] S2.2, TA received Then, calculate And Send to RU via secure channel i ;

[0030] S2.3, RU i Received Then, save (δ, M1, M2, V, HK) and... Split into two parts and satisfy

[0031]

[0032] S2.4, RU i calculate and Then RU i The public key is The private key is

[0033] S2.5, similar to S2.1-2.4, can generate CU. j The public key is pk cu The private key is sk cu ;

[0034] S2.6, Number of RSUs Selected calculate And If sent to TA via a secure channel, the RSU's public / private key pair is:

[0035] S2.7, Number of LSP selections calculate And If sent to TA via a secure channel, the LSP's public / private key pair is:

[0036] Preferably, step S3 has the following detailed description:

[0037] S3.1, RU i Randomly generated including the starting point end Location point set And construct a delta-position Bloom filter for it. At the beginning, each x i All are 0:

[0038] S3.2, RU i Using functions P nl Inserting the point in Then to If v i If ∈V is 0, then let x′ i =x″ i =x i Otherwise select a number make Final output and

[0039] S3.3, RU i calculate Output related to P ru Pairing index (PI′) ru ,PI″ ru )

[0040] S3.4, RU i Number of selections calculate and

[0041] S3.5, RU i Calculate L1 = H1(E1, ..., E4, PI′) ru ,PI″ ru ),

[0042] S3.6, RU i Output in

[0043] Preferably, step S4 includes the following detailed description:

[0044] S4.1, LSP receives RU i SQ sent i Then, verify SQ i Timestamp T ru If |T is not satisfied ru -T lsp If |≤ΔT, then reject the query; otherwise, proceed to the next step.

[0045] S4.2, LSP is calculated and L′1=H1(E1,E2,E′3,E4,PI′) ru ,PI′ ru To judge and Check if both conditions are met. If not, reject the query; otherwise, output the result. And send it to the RSU.

[0046] Preferably, step S5 includes the following detailed description:

[0047] S5.1, RSU receives SQ′ sent by LSP i Then, a coordination signal CS is broadcast to the surrounding CUs. j

[0048] S5.2, CU j Upon receiving the CS, a set of location points P that can provide location services is generated based on existing background knowledge. cu And construct a delta-position Bloom filter for it. At the beginning, each y j =0;

[0049] S5.3, CU i Using functions P cu Inserting the point in Then to If v j If ∈V is 1, then let y′ j =y″ j =y j Otherwise select a number make Final output profit

[0050] S5.4, CU j calculate Output related to P cu Pairing index (PI′) cu ,PI″ cu );

[0051] S5.5, CU j Calculate E″1, E″2, E″3, E″4 and L″1, L″2, and then... Send to RSU, where

[0052] S5.6, RSU received Afterwards, for CU i Perform identity and collaborative verification

[0053] S5.6.1, RSU through calculation and L″′1=H1(E″1,E″2,E″′3,E″4,PI′ cu ,PI″ cu To judge and Does it hold true at the same time? If not, reject CU. j Participate in the collaboration; otherwise, proceed to the next step.

[0054] S5.6.2, RSU calculates N = (PI′) cu ) T ·PI′ ru +(PI″ cu )T ·PI″ ru To judge Is it true? If not, reject CU. j Participate in collaboration; otherwise, report to CU j Send a verification success command;

[0055] S5.7, CU i After receiving the verification success command sent by the RSU, based on the location point set P cu Generate the corresponding location service And calculate

[0056]

[0057] Where f(x) = f0 + f1x + ... + f n -1x n-1 ;

[0058] S5.8, CU j Number of selections calculate

[0059]

[0060] Let O = (O1, O2, O3) and send it to RSU.

[0061] Preferably, step S6 includes the following detailed description:

[0062] S6.1, RSU receives data from n CUs j The generated location service ciphertext O;

[0063] S6.2, RSU by RU i Test trapdoor ET sent via secure channel;

[0064] S6.3, to RSU calculates Determine whether the following expression is true or false.

[0065]

[0066] If all the equations are true, then the process is interrupted, and the acceptance of these n CUs is refused. j Generate n location service ciphertexts O; otherwise, generate a location service response SR. i，j ={E″1,E″2,O1,O2,O3,PI′ cu ,PI″ cu} and send it to the LSP for storage.

[0067] Preferably, step S7 includes the following detailed description:

[0068] S7.1, RU, sends a location service search trapdoor ST = (PI′) to LSP. ru ,PI″ ru )

[0069] S7.2 After receiving ST, LSP calculates N = (PI′) cu ) T ·PI′ nu +(PI″ cu ) T ·PI″ ru To judge Whether it is valid or not.

[0070] S7.3 If there exists (PI′) that makes the expression true. cu ,PI″ cu If the associated service response SR is received, then the service response SR will be sent to it. i，j Send to RU i ;

[0071] S7.4, RU i Received SR i，j Then, calculate Then, you can search for relevant location services in S yourself.

[0072] Preferably, step S8 includes the following detailed description:

[0073] S8.1, If ​​user U exists k Stable RU i CU j When malicious behavior occurs, the TA calculates the following formula to obtain the user U who engaged in malicious behavior. k private key

[0074]

[0075] S8.2, Because TA knows the private key The correspondence between a user's identity and their identity can be used to reveal that user's identity.

[0076] S8.3, TA generates a public revocation list. To reject private key Reuse.

[0077] (III) Beneficial Effects

[0078] Compared with existing technologies, this invention provides a location privacy protection method based on collaborative services, which has the following beneficial effects:

[0079] 1. This location privacy protection method based on collaborative services differs from existing cryptography-based research schemes in that it provides location services to users with a higher level of security and achieves the following three goals: First, it uses a Bloom filter to build a secure index for users to provide secure location services; second, it ensures that users' location privacy is not leaked when responding to RSUs; and finally, it ensures that when any two users are engaged in collaborative services, neither user can infer the other's location privacy from the content of the collaborative service.

[0080] 2. This location privacy protection method based on collaborative services differs from existing k-anonymity-based research schemes in that it can protect user privacy and security while achieving lower communication overhead. Specifically, it utilizes secure one-way hash functions, pseudo-random functions, and Bloom filters to replace the previously required anonymity sets and cumbersome cryptographic algorithms that incur significant communication overhead when initiating location-based service queries, resulting in a communication overhead of approximately 1.39 kbytes. This offers a greater advantage over existing anonymity research schemes when dealing with a large user base.

[0081] 3. This location privacy protection method based on collaborative services, using a pairing (search) index built upon a Bloom filter, maintains a pairing efficiency of approximately 0.2146 seconds, which remains constant regardless of the number of user location points. To a certain extent, this invention can improve the efficiency of collaborative location services for users.

[0082] 4. This location privacy protection method based on collaborative services proposes a repeatability check based on ciphertext equivalence testing. This allows for the determination, in ciphertext mode, whether multiple collaborative service ciphertexts are encrypted using different public keys from the same plaintext. Furthermore, the repeatability check process does not disclose any plaintext information related to service recommendations, thus effectively protecting user privacy. Attached Figure Description

[0083] Figure 1 A schematic diagram of existing privacy protection schemes for connected vehicles based on anonymity and cryptography;

[0084] Figure 2 This is a schematic diagram of the process of the present invention;

[0085] Figure 3 This is a schematic diagram of the collaborative location service of the present invention;

[0086] Figure 4 RSU to CU of the present invention j Calculation diagram. Detailed Implementation

[0087] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0088] Please see Figure 2-4 The present invention provides the following technical solutions:

[0089] S1. System initialization: TA generates the system public key PK, system private key MSK, tracking key TK, and system parameters params;

[0090] S2, User Registration: RU i CU j RSU and LSP register with TA respectively, generating their own public-private key pairs;

[0091] S3, Service Inquiry: RU i Generate location service query sQ i And send it to the LSP via RSU;

[0092] S4. Query Verification: LSP receives RU i SQ sent i Next, its validity is verified. If the verification fails, the query is rejected; otherwise, the location service query SQ′ is executed. i Send to RSU;

[0093] S5, Proxy Service: The RSU receives the SQ′ sent by the LSP. i Then, a coordination signal CS is broadcast to the surrounding CUs. j and for RU i Perform proxy services, thereby communicating with CU j Data interaction is performed. During this process, CU... j Identity and collaboration verification must be performed with the RSU. For successfully verified CUs... j It generates a ciphertext O of a location service set S and sends it to RSU;

[0094] S6. Repeatability Test: RSU is conducted by RU i The test trapdoor ET sent through the secure channel is used to test n CUs. j The generated n location service ciphertexts O are subjected to repeatability testing. If the test passes, a location service response SR is generated. i,j And send it to the LSP for storage;

[0095] S7, Service Search: RU iA location service search trapdoor (ST) is sent to the LSP, and the LSP then returns the corresponding search results to the RU. i

[0096] S8. User Tracking: When a user engages in malicious behavior, their identity can be revealed through the tracking key TK.

[0097] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0098] S1. System initialization: TA generates the system public key PK, system private key MSK, and system parameters params;

[0099] S1.1 Given a security parameter, the generation order of TA is a prime number p (p≥2). λ A cyclic group of ), where g∈G is a generator;

[0100] SI.2. Given the security parameter δ, TA generates an invertible matrix. Vector V = {(v1, ..., v ...2, ..., v3, ..., v4, ..., v δ ) T |v i ∈ R {0, 1}}, hash key set Pseudo-random function F: {0, 1} * ×{0, 1} δ →{0,1} * and l independent position-sensitive hash functions

[0101]

[0102] S1.3, TA generates three secure hash functions. H2: {0, 1} * →{0,1} 2ρ H3: {0, 1} * →{0,1} λ ;

[0103] S1.4, Number of TA selections calculate

[0104] S1.5, TA generates the system public key PK = (h1, h2, h3), the system private key MSK = (α, M1, M2, V), the tracking key TK = (ξ1, ξ2) and the system parameters params = (G, p, e, g, PK, H1, H2, H3, H, F), where TA publishes the system parameters params and keeps the system private key MSK and the tracking key TK private.

[0105] S2, User Registration: RUi CU j RSU and LSP register with TA respectively, generating their own public-private key pairs;

[0106] S2.1, Number of RU selections calculate And Send it to TA via a secure channel;

[0107] S2.2, TA received Then, calculate And Send to RU via secure channel i ;

[0108] S2.3, RU i Received Then, save (δ, M1, M2, V, HK) and... Split into two parts and satisfy

[0109]

[0110] S2.4, RU i calculate and Then RU i The public key is The private key is

[0111] S2.5, similar to S2.1-2.4, can generate CU. j The public key is pk cu The private key is sk cu ;

[0112] S2.6, Number of RSUs Selected calculate And If sent to TA via a secure channel, the RSU's public / private key pair is:

[0113] S2.7, Number of LSP selections calculate And If sent to TA via a secure channel, the LSP's public / private key pair is:

[0114] To make the collaborative location service (S3-S7) of the present invention clearer, the following description is provided in conjunction with... Figure 3 The collaborative location service in this invention will be described in further detail below.

[0115] S3, Service Inquiry: RU i Generate location service query SQ i And send it to the LSP via RSU:

[0116] S3.1, RU i Randomly generated including the starting point end Location point set And construct a delta-position Bloom filter for it. At the beginning, each x i All are 0:

[0117] S3.2, RU i Using functions P nι Inserting the point in Then to If v i If ∈V is 0, then let x′ i =x″ i =x i Otherwise select a number make Final output and

[0118] S3.3, RU i calculate Output related to P ru Pairing index (PI′) ru ,PI″ ru )

[0119] S3.4, RU i Number of selections calculate and

[0120] S3.5, RU i Calculate L1 = H1(E1, ..., E4, PI′) ru ,PI″ ru ),

[0121] S3.6, RU i Output in

[0122] S4. Query Verification: LSP receives RU i SQ sent iNext, its validity is verified. If the verification fails, the query is rejected; otherwise, a location service query is initiated. Send to RSU:

[0123] S4.1, LSP receives RU i SQ sent i Then, verify SQ i Timestamp T ru If |T is not satisfied ru -T lsp If |≤ΔT, then reject the query; otherwise, proceed to the next step.

[0124] S4.2, LSP is calculated and L′1=H1(E1,E2,E′3,E4,PI′) ru ,PI′ ru To judge and Check if both conditions are met. If not, reject the query; otherwise, output the result. And send it to the RSU.

[0125] To explain S5 more clearly, the following will combine... Figure 4 Let's explain in more detail.

[0126] S5, Proxy Service: The RSU receives the SQ′ sent by the LSP. i Then, a coordination signal CS is broadcast to the surrounding CUs. j and for RU i Perform proxy services, thereby communicating with CU j Data interaction is performed. During this process, CU... j Identity and collaboration verification must be performed with the RSU. For successfully verified CUs... j It generates a ciphertext O of a location service set S and sends it to RSU;

[0127] S5.1, RSU receives SQ′ sent by LSP i Then, a coordination signal CS is broadcast to the surrounding CUs. j

[0128] S5.2, CU j Upon receiving the CS, a set of location points P that can provide location services is generated based on existing background knowledge. cu And construct a delta-position Bloom filter for it. At the beginning, each y j =0;

[0129] S5.3, CU i Using functions Pcu Inserting the point in Then to If v j If ∈V is 1, then let y′ j =y″ j =y j Otherwise select a number make

[0130] Final output profit

[0131] S5.4, CU j calculate Output related to P cu Pairing index (PI′) cu ,PI″ cu );

[0132] S5.5, CU j Calculate E″1, E″2, E″3, E″4 and L″1, L″2, and then... Send to RSU, where

[0133] S5.6, RSU received Afterwards, for CU i Perform identity and collaborative verification;

[0134] S5.6.1, RSU through calculation and L″′1=H1(E″1,E″2,E″′3,E″4,PI′ ru ,PI″ cu To judge and Does it hold true at the same time? If not, reject CU. j Participate in the collaboration; otherwise, proceed to the next step.

[0135] S5.6.2, RSU calculates N = (PI′) cu ) T ·PI′ ru +(PI″ cu ) T ·PI″ ru To judge Is it true? If not, reject CU. j Participate in collaboration; otherwise, report to CU j Send a verification success command;

[0136] S5.7, CU iAfter receiving the verification success command sent by the RSU, based on the location point set P cu Generate the corresponding location service And calculate

[0137]

[0138] Where f(x) = f0 + f1x + ... + f n -1x n-1 ;

[0139] S5.8, CU j Number of selections calculate

[0140]

[0141] Let O = (O1, O2, O3) and send it to RSU.

[0142] S6. Repeatability Test: RSU is conducted by RU i The test trapdoor ET sent through the secure channel is used to test n CUs. j The generated n location service ciphertexts O are subjected to repeatability testing. If the test passes, a location service response SR is generated. i,j And send it to the LSP for storage;

[0143] S6.1, RSU receives data from n CUs j The generated location service ciphertext O;

[0144] S6.2, RSU by RU i Test trapdoor ET sent via secure channel;

[0145] S6.3, to RSU calculates Determine whether the following expression is true or false.

[0146]

[0147] If all the equations are true, then the process is interrupted, and the acceptance of these n CUs is refused. j Generate n location service ciphertexts O; otherwise, generate a location service response SR. i,j ={E″1,E″2,O1,O2,O3,PI′ cu ,PI″ cu} and send it to the LSP for storage.

[0148] S7, Service Search: RU i A location service search trapdoor (ST) is sent to the LSP, and the LSP then returns the corresponding search results to the RU. i

[0149] S7.1, RU, sends a location service search trapdoor ST = (PI′) to LSP. ru ,PI″ ru )

[0150] S7.2 After receiving ST, LSP calculates N = (PI′) cu ) T ·PI′ nu +(PI″ cu ) T ·PI″ ru To judge Whether it is valid or not.

[0151] S7.3 If there exists (PI′) that makes the expression true. cu ,PI″ cu If the associated service response SR is received, then the service response SR will be sent to it. i，j Send to RU i ;

[0152] S7.4, RU i Received SR i，j Then, calculate Then, you can search for relevant location services in S yourself.

[0153] S8. User Tracking: When a user engages in malicious behavior, their identity can be revealed through the tracking key TK.

[0154] S8.1, If ​​user U exists k Stable RU i CU j When malicious behavior occurs, the TA calculates the following formula to obtain the user U who engaged in malicious behavior. k private key

[0155]

[0156] S8.2, Because TA knows the private key The correspondence between a user's identity and their identity can be used to reveal that user's identity.

[0157] S8.3, TA generates a public revocation list. To reject private key Reuse.

[0158] This location privacy protection method based on collaborative services differs from existing cryptography-based approaches in that it provides location services to users with a higher level of security and achieves the following three goals: First, it uses a Bloom filter to construct a secure index for users to provide secure location services; second, it ensures that users' location privacy is not disclosed when responding to RSUs (Real-Time Submissions); and finally, it ensures that when any two users are engaged in collaborative services, neither user can infer the other's location privacy from the content of the collaborative service.

[0159] Unlike existing k-anonymity-based research schemes, this approach offers lower communication overhead while protecting user privacy. Specifically, it utilizes secure one-way hash functions, pseudo-random functions, and Bloom filters to replace the previously costly anonymity sets and cumbersome cryptographic algorithms for initiating location-based service queries, resulting in a communication overhead of approximately 1.39 kbytes. This offers a significant advantage over existing anonymity research schemes, especially when dealing with large user groups.

[0160] The matching (search) index built based on Bloom filters maintains a matching efficiency of approximately 0.2146 seconds, which remains constant regardless of the number of user location points. To a certain extent, this invention can improve the efficiency of collaborative location services for users.

[0161] Repeated collaborative services not only fail to improve location service efficiency but also lead to resource waste. To address this, this invention presents a repeatability check based on ciphertext equivalence testing. This allows for the determination, in its ciphertext state, whether multiple collaborative service ciphertexts are encrypted using the same plaintext with different public keys. Furthermore, the repeatability check process does not disclose any plaintext information related to service recommendations, thus effectively protecting user privacy and security.

[0162] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for location privacy protection based on a cooperative service, characterized in that, Comprising the following steps: S1, system initialization: TA generates system public key PK, system private key MSK, tracking key TK and system parameters params; S2, User registration: RU i , CU j , RSU and LSP register to TA respectively, generate their own public-private key pairs; S3, service query: RU i generating a location service query SQ i and sending it to the LSP via the RSU; S4, query verification: LSP receives RU i Sent SQ i After, first verify its legality; If the verification fails, the query is rejected, otherwise the location service query SQ is sent to the RSU. i ′ S5, Proxy Service: The RSU receives the SQ sent by the LSP. i Afterwards, a coordination signal CS is broadcast to the surrounding CUs. j and for RU i Perform proxy services, thereby communicating with CU j Data interaction is performed; during this process, CU j Identity and collaboration verification must be performed with the RSU; for successfully verified CUs j It generates a ciphertext O of a location service set S and sends it to RSU; S6, Repetitive test: RSU by RU i Test trapdoor ET sent through the secure channel to n CUs j Generated n location service ciphertext O is subjected to repetitive test; if the test is passed, location service response SR is generated i,j and sent to LSP for storage; S7, service retrieval: RU i Send a location service search trap ST to LSP, and LSP returns the corresponding search result to RU i ; S8, user tracking: when the user appears malicious behavior, TA can reveal its identity through the tracking key TK.

2. The method of claim 1, wherein, In the S1, there are the following detailed description: S1.1, Given a security parameter λ, TA generates a cyclic group of prime order p (p≥2 λ ) of prime order p (p≥2 where is a generator; S1.2 Given the security parameter δ, TA generates an invertible matrix. Vector V = {(v1,…,v...} δ ) T |v i ∈ R {0,1}}, hash key set Pseudo-random function F:{0,1} * ×{0,1} δ →{0,1} * and position-sensitive hash function S1.3, the TA generates three secure hash functions H2: {0, 1} * → {0, 1} 2ρ and H3: {0, 1} * → {0, 1} λ ; S1.4, TA selection number Calculation S1.5, the TA generates a system public key PK = (hi, h2, h3), a system private key MSK = (a, Mi, M2, V), a tracing key TK = (xi, x2) and system parameters where the TA discloses the system parameters params, retains the system private key MSK and the tracing key TK. 3.The method of claim 1, wherein, In the S2, there are the following detailed description: S2.1, RU i Number of selections calculate And Send it to TA via a secure channel; S2.2, the TA receives Afterwards, the calculation and the is sent to the RU via a secure channel i ; S2.3, RU i receiving afterwards, saving and sending splitting into two parts and fulfilling S2.4, RU i computing and then the public key of RU i is the private key of RU S2.5, S2.1-2.4, can generate CU j The public key of the server is pk cu The private key of the server is sk cu ; S2.6, number of RSUs selected Calculate And send to TA through secure channel, then the public and private key pair of RSU is ​ S2.7, number of LSPs selected calculating and sending to the TA through the secure channel, then the public-private key pair of the LSP is ​ 4. The method of claim 1, wherein, In the S3, there are the following detailed description: S3.1, RU i Randomly generated including the starting point end Location point set And construct a delta-position Bloom filter for it. At the beginning, each x i All are 0; S3.2, RU i with function insert the point in into then if v i ∈ V is 0, let x i ′ = x i ″ = x i , otherwise select a number let finally output and S3.3, RU i computing outputting the pairing index (PI' ) of the first and second user equipments (UE1, UE2); and ru , PI" ru ). S3.4, RU i select number calculating and S3.5, RU i Compute L1= H1(E1,..., E4, PI r u , PI r u , ​​ S3.6, RU i output wherein 5. The method of claim 1, wherein, In the S4, there are the following detailed description: S4.1, LSP receives RU i sent SQ i , verify SQ i 's timestamp T ru ; if |T ru -T lsp |≤ΔT, reject the query; otherwise continue to next step; S4.2, LSP decides by computing and L'1 = H1(E1, E2, E'3, E4, PI' ru , PI" ru ) whether and are both true; if not, the query is rejected; otherwise, outputs and sends it to the RSU.

6. The method of claim 1, wherein, In the S5, there are the following detailed description: S5.1, the RSU receives the SQ sent by the LSP i , and then broadcasts a coordination signal CS to the surrounding CUs j ; S5.2, CU j Upon receiving the CS, generate the set of location points that can provide location service according to the existing background knowledge And construct a δ-bit Bloom filter for it At the beginning, each y j is 0; S5.3, CU j with function insert the point in then for if v j ∈ V is 1, let y′ j = y′ j ′ = y j , otherwise select a number let finally output and ​ S5.4, CU j computing outputting the pairing index (PI' ) of the CU cu , PI" cu ); S5.5, CU j E1", E2", E3", E4" and L1", L2" are calculated and sent to the RSU, where to the RSU, where S5.6, the RSU receives After the CU j identity and collaborative verification; S5.6.1, RSU through calculation and L″′1=H1(E″1,E″2,E″′3,E″4,PI′ cu ,PI″ cu To judge and Does it simultaneously hold true? If not, reject CU. j Participate in the collaboration; otherwise, proceed to the next step. S5.6.2, RSU calculates N = (PI′) cu ) T ·PI′ ru +(PI″ cu ) T ·PI″ ru To judge Is it true? If not, reject CU. j Participate in collaboration; otherwise, report to CU j Send a verification success command; S5.7, CU j Upon receiving the verification success instruction sent by the RSU, the location point set generate the corresponding location service and calculate where f(x) = f0+ f1x +... + f n-1 x n-1 ; S5.8, CU j Select number Compute Let O = (O1, O2, O3), and send it to the RSU.

7. The method of claim 1, wherein, In the S6, there are the following detailed description: S6.1, the RSU receives the n CU j The generated location service ciphertext O; S6.2, RSU by RU i Test trap ET sent over secure channel; S6.3, to RSU judges whether the following equation holds by calculating ​ If all the equations are true, the process is interrupted and the n CUs are rejected j The n position service cryptogram O is generated, otherwise the position service response SR is generated i,j ={E'1, E'2, O1, O2, O3, PI' cu , PI' cu}, and it is sent to the LSP for storage.

8. The method of claim 1, wherein, In the S7, there are the following detailed description: S7.1, RU i Send a location service search trap ST = (PI", PI") to the LSP ru , PI" ru ); S7.2, LSP receives ST, judges whether N = (PI" cu ) T · PI' ru + (PI" cu ) T · PI" ru is established or not. ​ S7.3, if there exists (PI', PI") such that the equation holds, then send the service response SR associated therewith to RU cu . cu . i,j i ​​ S7.4, RU i Upon receiving the SR i,j , the calculation Then the relevant location service is retrieved by itself in .

9. The method of claim 1, wherein, In the S8, there are the following detailed description: S8.1, if a user U exists k ∈ RU i ∪ CU j When malicious behavior occurs, the TA obtains the user U with the malicious behavior by calculating the following equation k Private key S8.2, since the TA knows the private key correspondence with the user's identity, the user's identity can be revealed thereby; S8.

3. The TA generates a public revocation list to deny re-use of the private key .

Images