Multi-real-time track privacy protection method and system

Abstract

The invention discloses a multi-real-time track privacy protection method and system, and belongs to the technical field of employee data management, and the method comprises the following steps: creating a plurality of block chains, setting an edge node for each block chain, and setting a position point threshold value; task information is received, and the edge node broadcasts and releases the task information through the block chain; receiving information uploaded by the mobile terminal is obtained, and the edge node generates path navigation information according to the position information of the mobile terminal; an edge node in a responsible area of the block chain sends a pseudonym to the mobile terminal, a local differential privacy technology and a multiple probability extension mechanism are used to process a motion track of the mobile terminal, the block chain stores information uploaded by the mobile terminal, and task data is determined through the information stored by the block; the method and the device have the effect of sending the task completion information to the mobile terminal corresponding to the task data.

Description

Technical Field

[0001] The present invention relates to the field of employee data management, and in particular to a multiple real-time trajectory privacy protection method and system. Background Art

[0002] At present, mobile crowdsourcing (MCS) technology has become an emerging technology in today's society. With the development of science and technology, mobile crowdsourcing platforms need to process a large amount of data every moment, and crowdsourcing platforms have good requirements for the real-time nature of data, such as traffic road conditions, temperature and humidity in various places, and pollution conditions. Traditional cloud computing can no longer meet the needs of crowdsourcing for real-time data and processing efficiency, so edge computing came into being. Edge computing can perform calculations at the edge of the network, greatly improving the efficiency and real-time nature of data processing. However, most crowdsourcing tasks are related to the location information of task participants. Therefore, the privacy of the location trajectory of task participants is likely to be stolen by attackers. Trajectory privacy is a special kind of personal privacy, which not only includes the sensitive information contained in the task participant's mobile trajectory itself, but also malicious attackers can deduce other personal information of the task participant through the task participant's mobile trajectory. Therefore, the protection of privacy trajectory is something that every mobile crowdsourcing platform needs to consider.

[0003] The above-mentioned existing technical solutions have the following defects: the current privacy track protection method is mainly based on confidentiality, which has the risk of being cracked and has poor security. Summary of the invention

[0004] In order to more securely protect the customer's trajectory information, the present application provides a multiple real-time trajectory privacy protection method and system.

[0005] On the one hand, the multiple real-time trajectory privacy protection method provided by this application adopts the following technical solution: A multiple real-time trajectory privacy protection method includes the following steps: Create multiple blockchains, set up edge nodes for each blockchain, divide each blockchain into responsible areas, and establish a pseudonym library to store pseudonyms; Set the location point threshold; Receive task information, including the task starting point, task end point, and task target, and upload the task information to the edge node according to the blockchain where the task information is located; Edge nodes publish task information through blockchain broadcast; The edge node obtains the receiving information uploaded by the mobile terminal, generates the path navigation information according to the location information of the mobile terminal, and sends the path navigation information to the mobile terminal; The edge node in the responsible area of ​​the blockchain sends a pseudonym to the mobile terminal, and the mobile terminal uploads information to the mobile terminal through the pseudonym; Receive location point information uploaded by the mobile terminal and record the number of location point uploads; The mobile trajectory is obtained based on the location point information, and the local differential privacy technology and multiple probability extension mechanism are used to process the movement trajectory of the mobile terminal to obtain the privacy trajectory; When the mobile terminal leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches the location point threshold, receiving the last location point information uploaded by the mobile terminal and the trajectory information corresponding to the pseudonym; The blockchain stores the information uploaded by the mobile terminal, and the task data is determined by the information stored in the block; Send task completion information to the mobile terminal corresponding to the task data.

[0006] By adopting the above solution, edge computing technology is introduced through blockchain, edge nodes are used to send and receive tasks and user location data, and privacy trajectories are obtained through local differential privacy technology and multiple probability extension mechanisms as the first level of trajectory protection. The user's movement trajectory is fragmented through multiple blockchains, and a pseudonym mechanism is used to obtain the fragmented movement trajectory as the second level of trajectory protection. Finally, task data is stored through blockchain to avoid data leakage on third-party platforms as the third level of trajectory protection, which effectively increases the difficulty of data cracking and improves the security of privacy data.

[0007] Preferably, the step of "using local differential privacy technology and multiple probability extension mechanisms to process the motion trajectory of the mobile terminal to obtain a privacy trajectory" also includes: Use local differential privacy technology to interfere with the location point information, and then probabilistically extend the motion trajectory from the processed location point to obtain a motion trajectory with multiple branches; The edge node divides the branch motion trajectory belonging to the area of ​​the blockchain it is responsible for into sub-motion trajectories, and uses all sub-motion trajectories as privacy trajectories.

[0008] By adopting the above scheme, local differential privacy technology can protect the privacy of data during the data collection stage, and obtain sub-motion trajectories by randomly extending the motion trajectory. The sub-motion trajectories can play a confusing role and further improve data security.

[0009] Preferably, the step of "sending a pseudonym to the mobile terminal by the edge node within the responsible area of ​​the blockchain" further includes: The edge node marks the sent pseudonym as deleted in the pseudonym library; The step of "receiving the last location point information and the trajectory information corresponding to the pseudonym uploaded by the mobile terminal" also includes: The edge node removes the mark of the received pseudonym in the pseudonym database, and the edge node no longer receives information uploaded by the pseudonym until the next time the pseudonym is sent.

[0010] By adopting the above scheme, the pseudonym mechanism can effectively eliminate the association between the identity of the task participant and the trajectory of the task participant, prevent link attacks, reduce the pseudonym storage consumption and ensure the real-time nature of the trajectory location.

[0011] Preferably, the step of "blockchain stores information uploaded by the mobile terminal, and determines task data through the information stored in the block" also includes: The edge node builds a Merkle tree in the blockchain and stores the information uploaded by the mobile terminal in the Merkle tree; After receiving the task query instruction, the edge node searches for the corresponding task data in the blockchain. The task data includes task information and task completion status, and sends the found task data back.

[0012] By adopting the above solution, the Merkle tree effectively reduces storage space and transmission costs, and can quickly and accurately capture data changes, effectively improving data security.

[0013] Preferably, the method further comprises the following steps: Set the upload interval time; After sending the pseudonym to the mobile terminal, the edge node receives the location information uploaded by the mobile terminal at every upload interval, and associates the pseudonym with the scope of responsibility of the blockchain; The responsibilities of blockchain are divided into marginal areas; Associating the location point information with the pseudonym, and judging whether the location point information is at the edge of the blockchain's scope of responsibility by the pseudonym; If the location point information is at the edge of the responsible range, and the last location point information uploaded by the pseudonym is not at the edge of the responsible range, the location point information count for the pseudonym will be canceled until the uploaded location point information leaves the edge of the responsible range or the pseudonym is withdrawn.

[0014] By adopting the above solution, each edge node has a range edge area, and the moving trajectory will not be interrupted when the location point information is in the range edge area, thereby avoiding the occurrence of a single location point or an extremely short moving trajectory.

[0015] On the other hand, the multiple real-time trajectory privacy protection system provided by this application adopts the following technical solutions: A multiple real-time trajectory privacy protection system includes multiple edge nodes and mobile terminals, each edge node includes a blockchain, and the edge node includes a data storage module, a pseudonym storage module, a task publishing module, a task assignment module, a trajectory recording module and a task processing module; The data storage module stores the responsible area and location point threshold of the corresponding blockchain; The pseudonym storage module stores a plurality of pseudonyms; The task publishing module receives task information, which includes the task starting point, task end point, and task target, sends the task information to the corresponding edge node according to the blockchain where the task information is located, and publishes the task information to the mobile terminal through blockchain broadcast; The task assignment module receives the receiving information uploaded by the mobile terminal, generates the path navigation information according to the location information of the mobile terminal, calls the pseudonym of the pseudonym storage module, and sends the pseudonym and the path navigation information to the mobile terminal; The trajectory recording module receives the location point information uploaded by the mobile terminal using a pseudonym, and records the number of location point uploads, obtains the mobile trajectory according to the location point information, processes the motion trajectory of the mobile terminal using local differential privacy technology and a multiple probability extension mechanism, obtains the privacy trajectory, associates the privacy trajectory with the mobile terminal and sends it to the data storage module. When the mobile terminal leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches the location point threshold, the last location point information uploaded by the mobile terminal and the trajectory information corresponding to the pseudonym are received, and the trajectory information is sent to the data storage module; The task processing module calls the task information and track information stored in the data storage module, generates task data according to the task information and track information, and displays the task data. When the task processing module receives the task completion information, it sends the task completion information to the mobile terminal.

[0016] By adopting the above solution, edge computing technology is introduced through blockchain, edge nodes are used to send and receive tasks and user location data, and privacy trajectories are obtained through local differential privacy technology and multiple probability extension mechanisms as the first level of trajectory protection. The user's movement trajectory is fragmented through multiple blockchains, and a pseudonym mechanism is used to obtain the fragmented movement trajectory as the second level of trajectory protection. Finally, task data is stored through blockchain to avoid data leakage on third-party platforms as the third level of trajectory protection, which effectively increases the difficulty of data cracking and improves the security of privacy data.

[0017] Preferably, the trajectory recording module uses local differential privacy technology to perform interference processing on the location point information, and then probabilistically extends the motion trajectory from the processed location point to obtain a motion trajectory with multiple branches. The trajectory recording module divides the branch motion trajectory belonging to the responsible area of ​​the blockchain into sub-motion trajectories, and uses all sub-motion trajectories as privacy trajectories.

[0018] By adopting the above scheme, local differential privacy technology can protect the privacy of data during the data collection stage, and obtain sub-motion trajectories by randomly extending the motion trajectory. The sub-motion trajectories can play a confusing role and further improve data security.

[0019] Preferably, when the mobile terminal leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches the location point threshold, the track recording module transmits the pseudonym of the mobile terminal to the pseudonym storage module, and no longer receives information uploaded by the pseudonym until the next time the pseudonym is sent; The pseudonym storage module marks the called pseudonym as deleted, refuses to send the pseudonym marked as deleted to the task assignment module, and the pseudonym storage module removes the mark of the received pseudonym.

[0020] By adopting the above scheme, the pseudonym mechanism can effectively eliminate the association between the identity of the task participant and the trajectory of the task participant, prevent link attacks, reduce the pseudonym storage consumption and ensure the real-time nature of the trajectory location.

[0021] Preferably, the data storage module constructs a Merkle tree and stores the received trajectory information in the Merkle tree; The task processing module receives the task query instruction, calls the task data stored in the data storage module according to the task query instruction, the task data includes task information and task completion status, and sends the found task data back.

[0022] By adopting the above solution, the Merkle tree effectively reduces storage space and transmission costs, and can quickly and accurately capture data changes, effectively improving data security.

[0023] Preferably, the data storage module stores the upload interval duration; The task assignment module uploads the interval duration every interval, and the edge node receives the location point information uploaded by the mobile terminal, and associates the pseudonym with the responsible scope of the blockchain; The track recording module associates the location point information with the pseudonym, and determines whether the location point information is in the edge area of ​​the responsible scope of the blockchain through the pseudonym. If the location point information is in the edge area of ​​the responsible scope, and the last location point information uploaded by the pseudonym is not in the edge area of ​​the responsible scope, the location point information count of the pseudonym is canceled until the uploaded location point information leaves the edge area of ​​the responsible scope or the pseudonym is withdrawn.

[0024] By adopting the above solution, each edge node has a range edge area, and the moving trajectory will not be interrupted when the location point information is in the range edge area, thereby avoiding the occurrence of a single location point or an extremely short moving trajectory.

[0025] In summary, the present invention has the following beneficial effects: 1. Obtain privacy trajectories through local differential privacy technology and multiple probability extension mechanisms, fragment the user's movement trajectory through multiple blockchains, and use a pseudonym mechanism to obtain fragmented movement trajectories. Finally, store task data through blockchain to prevent data leakage from third-party platforms, effectively increase the difficulty of data cracking, and improve the security of privacy data. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is an overall system block diagram of the second embodiment of the present application.

[0027] Figure 2 This is a module block diagram of the edge node of the second embodiment of the present application.

[0028] Description of reference numerals: 1. Edge node; 11. Data storage module; 12. Pseudonym storage module; 13. Task release module; 14. Task assignment module; 15. Trajectory recording module; 16. Task processing module; 2. Mobile terminal. DETAILED DESCRIPTION

[0029] Embodiment 1: This embodiment of the present application discloses a method for protecting privacy of multiple real-time trajectories. The specific steps are as follows: S100, create multiple blockchains, set an edge node 1 for each blockchain, divide each blockchain into responsible areas, and establish a pseudonym library storing pseudonyms.

[0030] S101. Set the location point threshold and upload interval. The location point threshold is set by the staff according to the block size and the computing power of edge node 1, and can be set to any integer around 10. The upload interval is set by the staff according to the task type. For example, the upload interval for short-distance food delivery can be set to about half a minute, and the upload interval for long-distance taxi service can be set to 1-2 minutes.

[0031] S200, receiving task information, the task information includes the task starting point, task end point, and task target, and uploading the task information to edge node 1 according to the blockchain where the task information is located.

[0032] S201. Edge node 1 publishes task information through blockchain broadcast.

[0033] S300, receiving information uploaded by mobile terminal 2 is obtained, and edge node 1 generates path navigation information according to the location information of mobile terminal 2, and sends the path navigation information to mobile terminal 2. According to the selected map system (such as Google Maps, Baidu Maps, etc.), the location information of mobile terminal 2 is marked as the starting point coordinates on the map system, and the target location of the task information is marked as the end point coordinates, and the coordinate values ​​of the location coordinates and the end point coordinates are obtained on the map system. The shortest path is calculated by a path algorithm (Dijkstra algorithm or A algorithm can be selected), and the shortest path is displayed on the map system to obtain the path navigation information.

[0034] S301. In the responsible area of ​​the blockchain, the edge node 1 sends a pseudonym to the mobile terminal 2, and the mobile terminal 2 uploads information to the mobile terminal 2 through the pseudonym. The edge node 1 marks the sent pseudonym as deleted in the pseudonym library.

[0035] S400. After sending the pseudonym to the mobile terminal 2, the edge node 1 receives the location information uploaded by the mobile terminal 2 at each upload interval, and the edge node 1 associates the pseudonym with the scope of responsibility of the blockchain.

[0036] S401. Divide the scope of responsibility of the blockchain into edge areas.

[0037] S402, receiving the location point information uploaded by the mobile terminal 2, and recording the number of times the location point is uploaded.

[0038] S403: Obtain a moving trajectory according to the location point information, use local differential privacy technology to perform interference processing on the location point information, and then probabilistically extend the movement trajectory from the processed location point to obtain a movement trajectory with multiple branches.

[0039] S404. Edge node 1 divides the branch motion trajectory belonging to the responsible area of ​​the blockchain into sub-motion trajectories, and uses all sub-motion trajectories as privacy trajectories.

[0040] S500. When the mobile terminal 2 leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches the location point threshold, the last location point information uploaded by the mobile terminal 2 and the trajectory information corresponding to the pseudonym are received.

[0041] S501. Associate the location point information with the pseudonym, and determine whether the location point information is at the edge of the responsible scope of the blockchain through the pseudonym.

[0042] S502. If the location point information is at the edge of the responsible scope, and the last location point information uploaded by the pseudonym is not at the edge of the responsible scope, the location point information count of the pseudonym is canceled until the uploaded location point information leaves the edge of the responsible scope or the pseudonym is withdrawn.

[0043] S503, edge node 1 removes the mark of the received pseudonym in the pseudonym library, and edge node 1 no longer receives the information uploaded by the pseudonym until the next time the pseudonym is sent. The pseudonym mechanism can effectively eliminate the association between the identity of the task participant and the task participant's trajectory, prevent link attacks, and reduce the pseudonym storage consumption and ensure the real-time nature of the trajectory position.

[0044] S600, edge node 1 constructs a Merkle tree in the blockchain, the blockchain stores the information uploaded by the mobile terminal 2, and the information uploaded by the mobile terminal 2 is stored in the Merkle tree.

[0045] S601. After receiving the task query instruction, edge node 1 searches for the corresponding task data in the blockchain. The task data includes task information and task completion status, and sends the found task data back.

[0046] S700, sending task completion information to the mobile terminal 2 corresponding to the task data.

[0047] The implementation principle of a multiple real-time trajectory privacy protection method in an embodiment of the present application is as follows: edge computing technology is introduced through blockchain, edge node 1 is used to send and receive tasks and user location data, and privacy trajectories are obtained as the first level of trajectory protection through local differential privacy technology and multiple probability extension mechanisms. The user's motion trajectory is fragmented through multiple blockchains, and a pseudonym mechanism is used to obtain the fragmented motion trajectory as the second level of trajectory protection. Finally, task data is stored through blockchain to prevent data leakage from a third-party platform as the third level of trajectory protection, which effectively increases the difficulty of data cracking and improves the security of privacy data.

[0048] Embodiment 2: This application embodiment discloses a multiple real-time trajectory privacy protection system, such as Figure 1 and Figure 2 As shown, it includes multiple edge nodes 1 and mobile terminals 2, and each edge node 1 includes a blockchain. The edge node 1 includes a data storage module 11, a pseudonym storage module 12, a task publishing module 13, a task assignment module 14, a track recording module 15 and a task processing module 16.

[0049] like Figure 2As shown, the data storage module 11 stores the responsible area, location point threshold, and upload interval duration of the corresponding blockchain. The location point threshold is set by the staff according to the block division size and the computing power of the edge node 1, and can be set to any integer of about 10. The upload interval duration is set by the staff according to the task type. For example, the upload interval duration of short-distance takeaway delivery can be set to about half a minute, and the long-distance taxi service can be set to 1-2 minutes. The data storage module 11 constructs a Merkle tree and stores the received trajectory information in the Merkle tree. The pseudonym storage module 12 stores multiple pseudonyms. The pseudonym storage module marks the pseudonym to be called as deleted, refuses to send the pseudonym marked as deleted to the task assignment module 14, and the pseudonym storage module removes the mark of the received pseudonym. The pseudonym mechanism can effectively eliminate the association between the identity of the task participant and the trajectory of the task participant, prevent link attacks, and can reduce the pseudonym storage consumption and ensure the real-time nature of the trajectory position. The Merkle tree effectively reduces the storage space and transmission cost, and can quickly and accurately capture data changes, effectively improving data security.

[0050] like Figure 2 As shown, the task publishing module 13 receives the task information, which includes the task starting point, task end point, and task target. The task information is sent to the corresponding edge node 1 according to the blockchain where the task information is located, and the task information is broadcast to the mobile terminal 2 through the blockchain. The task assignment module 14 receives the received information uploaded by the mobile terminal 2, generates the path navigation information according to the location information of the mobile terminal 2, calls the pseudonym of the pseudonym storage module, and sends the pseudonym and the path navigation information to the mobile terminal 2. The task assignment module 14 uploads the interval time every interval, and the edge node 1 receives the location point information uploaded by the mobile terminal 2, and associates the pseudonym with the responsible scope of the blockchain. According to the selected map system (such as Google Maps, Baidu Maps, etc.), the location information of the mobile terminal 2 is marked as the starting point coordinates on the map system, and the target location of the task information is marked as the end point coordinates. The coordinate values ​​of the location coordinates and the end point coordinates are obtained on the map system, and the shortest path is calculated by the path algorithm (Dijkstra algorithm or A algorithm can be selected), and the shortest path is displayed on the map system to obtain the path navigation information.

[0051] like Figure 2As shown, the trajectory recording module 15 receives the location point information uploaded by the mobile terminal 2 through the pseudonym, records the number of location point uploads, and obtains the movement trajectory according to the location point information. The trajectory recording module 15 uses the local differential privacy technology to interfere with the location point information, and then probabilistically extends the motion trajectory from the processed location point to obtain a motion trajectory with multiple branches. The trajectory recording module 15 divides the branch motion trajectory belonging to the responsible area of ​​the blockchain into sub-motion trajectories, and uses all sub-motion trajectories as privacy trajectories. The privacy trajectory is associated with the mobile terminal 2 and sent to the data storage module 11. When the mobile terminal 2 leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches the location point threshold, the last location point information uploaded by the mobile terminal 2 and the trajectory information corresponding to the pseudonym are received, and the trajectory information is sent to the data storage module 11. When the mobile terminal 2 leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches the location point threshold, the trajectory recording module 15 transmits the pseudonym of the mobile terminal 2 to the pseudonym storage module, and no longer receives the information uploaded by the pseudonym until the pseudonym is sent next time. Local differential privacy technology can protect data privacy during the data collection stage. The motion trajectory is randomly extended to obtain sub-motion trajectories. The sub-motion trajectories can play a confusing role and further improve data security.

[0052] like Figure 2 As shown, the track recording module 15 associates the location point information with the pseudonym, and determines whether the location point information is in the edge area of ​​the responsible range of the blockchain through the pseudonym. If the location point information is in the edge area of ​​the responsible range, and the last location point information uploaded by the pseudonym is not in the edge area of ​​the responsible range, the location point information count of the pseudonym is canceled until the uploaded location point information leaves the edge area of ​​the responsible range or the pseudonym is withdrawn. Each edge node 1 has a range edge area, and the movement trajectory will not be interrupted when the location point information is in the range edge area, avoiding the appearance of a single location point or a very short movement trajectory.

[0053] like Figure 2 As shown, the task processing module 16 calls the task information and track information stored in the data storage module 11, generates task data based on the task information and track information, and displays the task data. When the task processing module 16 receives the task query instruction, it calls the task data stored in the data storage module 11 according to the task query instruction. The task data includes task information and task completion status, and sends the found task data back. After the task processing module 16 receives the task completion information, it sends the task completion information to the mobile terminal 2.

[0054] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multiple real-time trajectory privacy protection method, characterized in that: The following steps are involved: Create multiple blockchains, set up edge nodes for each blockchain (1), divide each blockchain into responsible areas, and establish a pseudonym library for storing pseudonyms; Set the location point threshold; Receive task information, including the task starting point, task end point, and task target, and upload the task information to the edge node according to the blockchain where the task information is located (1); Edge nodes (1) publish task information through blockchain broadcast; Obtaining the receiving information uploaded by the mobile terminal (2), the edge node (1) generates path navigation information according to the location information of the mobile terminal (2), and sends the path navigation information to the mobile terminal (2); The edge node (1) in the responsible area of ​​the blockchain sends a pseudonym to the mobile terminal (2), and the mobile terminal (2) uploads information to the mobile terminal (2) through the pseudonym; receiving location point information uploaded by the mobile terminal (2) and recording the number of times the location point has been uploaded; Obtain the movement trajectory based on the location point information, and use local differential privacy technology and multiple probability extension mechanisms to process the movement trajectory of the mobile terminal (2) to obtain a private trajectory; When the mobile terminal (2) leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches the location point threshold, receiving the last location point information uploaded by the mobile terminal (2) and the trajectory information corresponding to the pseudonym; The blockchain stores the information uploaded by the mobile terminal (2), and determines the task data through the information stored in the block; Send task completion information to the mobile terminal (2) corresponding to the task data.

2. A method for protecting privacy of multiple real-time trajectories according to claim 1, characterized in that: The step of "using local differential privacy technology and multiple probability extension mechanisms to process the motion trajectory of the mobile terminal (2) to obtain a privacy trajectory" also includes: Use local differential privacy technology to interfere with the location point information, and then probabilistically extend the motion trajectory from the processed location point to obtain a motion trajectory with multiple branches; The edge node (1) divides the branch motion trajectory belonging to the responsible area of ​​the blockchain into sub-motion trajectories, and uses all sub-motion trajectories as privacy trajectories.

3. A multiple real-time trajectory privacy protection method according to claim 1, characterized in that: The step of "sending a pseudonym from the edge node (1) to the mobile terminal (2) within the responsible area of ​​the blockchain" also includes: The edge node (1) marks the sent pseudonym as deleted in the pseudonym database; The step of "receiving the last location point information and the track information corresponding to the pseudonym uploaded by the mobile terminal (2)" also includes: The edge node (1) removes the mark of the received pseudonym in the pseudonym database, and the edge node (1) no longer receives information uploaded by the pseudonym until the pseudonym is sent next time.

4. A method for protecting privacy of multiple real-time trajectories according to claim 1, characterized in that: The step of "blockchain stores information uploaded by the mobile terminal (2), and determining task data through the information stored in the block" also includes: The edge node (1) constructs a Merkle tree in the blockchain and stores the information uploaded by the mobile terminal (2) in the Merkle tree; After receiving the task query instruction, the edge node (1) searches for the corresponding task data in the blockchain. The task data includes task information and task completion status, and sends the found task data back.

5. A method for protecting privacy of multiple real-time trajectories according to claim 2, characterized in that: The following steps are also included: Set the upload interval time; After sending the pseudonym to the mobile terminal (2), the edge node (1) receives the location point information uploaded by the mobile terminal (2) at every upload interval, and the edge node (1) associates the pseudonym with the scope of responsibility of the blockchain; The responsibilities of blockchain are divided into marginal areas; Associating the location point information with the pseudonym, and judging whether the location point information is at the edge of the blockchain's scope of responsibility by the pseudonym; If the location point information is at the edge of the responsible range, and the last location point information uploaded by the pseudonym is not at the edge of the responsible range, the location point information count for the pseudonym will be canceled until the uploaded location point information leaves the edge of the responsible range or the pseudonym is withdrawn.

6. A multiple real-time trajectory privacy protection system, characterized by: The invention comprises a plurality of edge nodes (1) and a mobile terminal (2), each edge node (1) comprises a blockchain, and the edge node (1) comprises a data storage module (11), a pseudonym storage module (12), a task publishing module (13), a task assignment module (14), a track recording module (15) and a task processing module (16); The data storage module (11) stores the responsible area and location point threshold of the corresponding blockchain; The pseudonym storage module (12) stores a plurality of pseudonyms; The task publishing module (13) receives task information, which includes a task starting point, a task end point, and a task target, sends the task information to a corresponding edge node (1) according to the blockchain where the task information is located, and publishes the task information to the mobile terminal (2) through blockchain broadcasting; The task assignment module (14) receives the reception information uploaded by the mobile terminal (2), generates path navigation information according to the location information of the mobile terminal (2), calls the pseudonym of the pseudonym storage module, and sends the pseudonym and the path navigation information to the mobile terminal (2); The trajectory recording module (15) receives the location point information uploaded by the mobile terminal (2) using a pseudonym, records the number of location point uploads, obtains a movement trajectory based on the location point information, processes the movement trajectory of the mobile terminal (2) using local differential privacy technology and a multiple probability extension mechanism, obtains a privacy trajectory, associates the privacy trajectory with the mobile terminal (2) and sends it to the data storage module (11); when the mobile terminal (2) leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches a location point threshold, receives the last location point information uploaded by the mobile terminal (2) and the trajectory information corresponding to the pseudonym, and sends the trajectory information to the data storage module (11); The task processing module (16) calls the task information and track information stored in the data storage module (11), generates task data according to the task information and track information, and displays the task data. When the task processing module (16) receives the task completion information, it sends the task completion information to the mobile terminal (2).

7. A multiple real-time trajectory privacy protection system according to claim 6, characterized in that: The trajectory recording module (15) uses local differential privacy technology to perform interference processing on the location point information, and then probabilistically extends the motion trajectory from the processed location point to obtain a motion trajectory with multiple branches. The trajectory recording module (15) divides the branch motion trajectory belonging to the responsible area of ​​the blockchain into sub-motion trajectories, and uses all sub-motion trajectories as privacy trajectories.

8. A multiple real-time trajectory privacy protection system according to claim 6, characterized in that: The track recording module (15) transmits the pseudonym of the mobile terminal (2) to the pseudonym storage module when the mobile terminal (2) leaves the responsible area of ​​the blockchain or the number of recorded location point uploads reaches the location point threshold, and no longer receives information uploaded by the pseudonym until the pseudonym is sent next time; The pseudonym storage module marks the pseudonym to be called as deleted, refuses to send the pseudonym marked as deleted to the task assignment module (14), and the pseudonym storage module removes the mark of the received pseudonym.

9. A multiple real-time trajectory privacy protection system according to claim 6, characterized in that: The data storage module (11) constructs a Merkle tree and stores the received trajectory information in the Merkle tree; The task processing module (16) receives a task query instruction, calls the task data stored in the data storage module (11) according to the task query instruction, the task data including task information and task completion status, and sends back the found task data.

10. A multiple real-time trajectory privacy protection system according to claim 8, characterized in that: The data storage module (11) stores the upload interval duration; The task assignment module (14) uploads the interval time at each interval, and the edge node (1) receives the location point information uploaded by the mobile terminal (2), and associates the pseudonym with the responsible scope of the blockchain; The track recording module (15) associates the location point information with the pseudonym, and determines whether the location point information is in the edge area of ​​the responsible scope of the blockchain through the pseudonym. If the location point information is in the edge area of ​​the responsible scope, and the last location point information uploaded by the pseudonym is not in the edge area of ​​the responsible scope, the location point information count of the pseudonym is cancelled until the uploaded location point information leaves the edge area of ​​the responsible scope or the pseudonym is withdrawn.

Images