A multiple real-time trajectory privacy protection method and system

Abstract

The application discloses a kind of multiple real-time trajectory privacy protection method and system, belong to the technical field of staff data management, it includes the following steps: creating multiple blockchains, setting edge node for each blockchain, set position point threshold;Receive task information, edge node is published through blockchain broadcast task information;Get the receiving information uploaded by mobile terminal, and the edge node generates path navigation according to the location information of mobile terminal;Edge node sends pseudonym to mobile terminal in the responsible area of blockchain, uses local differential privacy technology and multiple probability extension mechanism to process the motion trajectory of mobile terminal, and the blockchain stores the information uploaded by mobile terminal, determines task data by the information stored by block;The application has the effect of sending task completion information to the mobile terminal corresponding to task data.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of employee data management, and in particular to a multi-real-time trajectory privacy protection method and system. BACKGROUND

[0002] At present, mobile crowdsourcing (MCS) technology has become a new technology in today's society. With the development of science and technology, the mobile crowdsourcing platform needs to process a large amount of data every moment, and the real-time requirement of the data of the crowdsourcing platform is relatively good, such as traffic road conditions, local weather temperature and humidity, and pollution conditions, etc. The traditional cloud computing cannot meet the demand of crowdsourcing for real-time data and processing efficiency, therefore, edge computing emerges as the times require. Edge computing can perform calculation at the edge of the network, greatly improving the efficiency and real-time performance of data processing. However, most crowdsourcing tasks are related to the location information of the task participants, so the location trajectory privacy of the task participants may be stolen by attackers. Trajectory privacy is a special kind of personal privacy, which not only includes sensitive information contained in the mobile trajectory of the task participants, but also malicious attackers can deduce other personal information of the task participants through the mobile trajectory of the task participants, so the protection of the privacy trajectory is a matter that needs to be considered by every mobile crowdsourcing platform.

[0003] The prior art in the above has the following defects: the current privacy trajectory protection method mainly focuses on security, which has the risk of being cracked and poor security. SUMMARY

[0004] In order to more safely protect the trajectory information of customers, the present application provides a multi-real-time trajectory privacy protection method and system.

[0005] On the one hand, the multi-real-time trajectory privacy protection method provided by the present application adopts the following technical solution:

[0006] A multi-real-time trajectory privacy protection method, comprising the following steps:

[0007] Creating a plurality of blockchains, setting edge nodes for each blockchain, dividing responsible areas for each blockchain, and establishing a pseudonym library storing pseudonyms;

[0008] Setting a position point threshold and an upload interval length;

[0009] Receiving task information, the task information including a task starting point, a task end point and a task target, uploading the task information to the edge nodes according to the blockchain where the task information is located;

[0010] The edge nodes broadcast and publish the task information through the blockchain;

[0011] Acquiring the location information uploaded by the mobile terminal, and generating path navigation information according to the location information of the mobile terminal, and sending the path navigation information to the mobile terminal by the edge node;

[0012] The edge node sends a pseudonym to the mobile terminal in the responsible area of the blockchain, and the mobile terminal uploads information to the mobile terminal through the pseudonym, and the edge node receives the location point information uploaded by the mobile terminal every interval interval length, and the edge node associates the pseudonym with the responsible range of the blockchain;

[0013] The responsible range of the blockchain is divided into a range edge area;

[0014] Receiving the location point information uploaded by the mobile terminal and recording the number of times of uploading the location point;

[0015] According to the location point information, the movement trajectory of the mobile terminal is obtained, and the local differential privacy technology and the multiple probability extension mechanism are used to process the movement trajectory of the mobile terminal to obtain a private trajectory;

[0016] When the mobile terminal leaves the responsible area of the blockchain or the number of times of uploading the recorded location point 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;

[0017] The location point information is associated with the pseudonym, and whether the location point information is in the edge area of the responsible range of the blockchain is judged through the pseudonym;

[0018] If the location point information is in the edge area of the responsible range, and the last location point information uploaded by the mobile terminal is not in the edge area of the responsible range, the counting of the location point information of the pseudonym is cancelled, until the uploaded location point information is out of the edge area of the responsible range or the pseudonym is withdrawn.

[0019] By using the above scheme, the edge computing technology is introduced through the blockchain, the edge node is used to receive and send tasks and user location data, the local differential privacy technology and the multiple probability extension mechanism are used to obtain a private trajectory as the first trajectory protection, the user's movement trajectory is fragmented through multiple blockchains, and the fragmented movement trajectory is obtained through the pseudonym mechanism as the second trajectory protection, and finally the task data is stored through the blockchain to avoid data leakage by a third party platform as the third trajectory protection, thereby effectively increasing the data cracking difficulty and improving the security of the private data. Each edge node has a range edge area, and the movement trajectory will not be interrupted when the location point information is in the range edge area, so as to avoid the occurrence of a single location point or a very short movement trajectory.

[0020] Preferably, the step of "using local differential privacy technology and multiple probability extension mechanism to process the movement trajectory of the mobile terminal to obtain a private trajectory" comprises:

[0021] The local differential privacy technology is used to interfere with the location point information, and a motion trajectory with multiple branches is obtained by extending the motion trajectory from the processed location point.

[0022] The edge node divides the branch motion trajectory belonging to the responsible area of the blockchain into sub-motion trajectories, and takes all the sub-motion trajectories as private trajectories.

[0023] By using the above scheme, the local differential privacy technology can protect the data privacy in the data collection stage, and the sub-motion trajectory obtained by extending the motion trajectory randomly can further improve the data security.

[0024] Preferably, the step of "sending a pseudonym to the mobile terminal by the edge node in the responsible area of the blockchain" comprises:

[0025] The edge node marks the sent pseudonym as deleted in the pseudonym library;

[0026] The step of "receiving the uploaded last location point information and trajectory information corresponding to the pseudonym by the mobile terminal" further comprises:

[0027] The edge node removes the mark of the received pseudonym in the pseudonym library, and the edge node no longer receives the information uploaded by the pseudonym until the next time the pseudonym is sent.

[0028] By using 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, and reduce the storage consumption of the pseudonym and ensure the real-time of the trajectory position.

[0029] Preferably, the method further comprises the following steps:

[0030] The edge node constructs a Merkle tree in the blockchain, and stores the information uploaded by the mobile terminal in the Merkle tree;

[0031] After receiving the task query instruction, the edge node searches for the corresponding task data in the blockchain, the task data including the task information and the task completion status, and sends the searched task data back;

[0032] The task completion information is sent to the mobile terminal corresponding to the task data.

[0033] By using the above scheme, the Merkle tree effectively reduces the storage space and transmission cost, and can quickly and accurately capture data changes, effectively improving the data security.

[0034] On the other hand, the multi-real-time trajectory privacy protection system provided by the present application adopts the following technical scheme:

[0035] A multiple real-time trajectory privacy protection system, comprising a plurality of edge nodes and mobile terminals, each edge node comprising a blockchain, the edge node comprising a data storage module, a pseudonym storage module, a task publishing module, a task assigning module, and a trajectory recording module;

[0036] The data storage module stores the responsible area of the corresponding blockchain, the location point threshold value, and the upload interval duration;

[0037] The pseudonym storage module stores a plurality of pseudonyms;

[0038] The task publishing module receives task information, which includes the task starting point, the task ending point, and the task target, and sends the task information to the corresponding edge node according to the blockchain on which the task information is located, and publishes the task information to the mobile terminal through blockchain broadcasting;

[0039] The task assigning module receives the location information uploaded by the mobile terminal, generates path navigation information according to the location information of the mobile terminal, calls the pseudonym of the pseudonym storage module, sends the pseudonym and the path navigation information to the mobile terminal, and the task assigning module receives the location point information uploaded by the mobile terminal every interval upload interval duration, and associates the pseudonym with the responsible range of the blockchain;

[0040] The trajectory recording module receives the location point information uploaded by the mobile terminal through the pseudonym, records the number of times of uploading the location point, obtains the mobile trajectory according to the location point information, processes the movement trajectory of the mobile terminal using the local differential privacy technology and the multiple probability extension mechanism, obtains the privacy trajectory, associates the privacy trajectory with the mobile terminal, and sends the privacy trajectory to the data storage module; when the mobile terminal leaves the responsible area of the blockchain or the number of times of uploading the location point reaches the location point threshold value, the trajectory recording module receives the last location point information uploaded by the mobile terminal and the trajectory information corresponding to the pseudonym, and sends the trajectory information to the data storage module; the trajectory recording module associates the location point information with the pseudonym, judges whether the location point information is in the edge area of the responsible range of the blockchain through the pseudonym, and if the location point information is in the edge area of the responsible range and the last location point information uploaded by the mobile terminal is not in the edge area of the responsible range, cancels the counting of the location point information of the pseudonym, until the uploaded location point information is out of the edge area of the responsible range or the pseudonym is withdrawn. Each edge node has a range edge area, and the mobile 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.

[0041] By adopting the above scheme, the edge computing technology is introduced through the blockchain, the edge node is used to transmit task and user location data, the local differential privacy technology and the multiple probability extension mechanism are used to obtain the privacy trajectory as the first trajectory protection, the user's motion trajectory is fragmented through multiple blockchains, and the fragmented motion trajectory is obtained through the pseudonym mechanism as the second trajectory protection, and finally the task data is stored through the blockchain to avoid data leakage by a third-party platform as the third trajectory protection, thereby effectively increasing the data cracking difficulty and improving the security of the privacy data.

[0042] Preferably, the trajectory recording module uses the local differential privacy technology to interfere with the location point information, and then 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 a sub-motion trajectory, and takes all the sub-motion trajectories as the privacy trajectory.

[0043] By adopting the above scheme, the local differential privacy technology can protect the data in the data collection stage, and the sub-motion trajectory is obtained after the motion trajectory is randomly extended, so that the sub-motion trajectory can play a confusing role and further improve the data security.

[0044] Preferably, the trajectory recording module transmits the pseudonym of the mobile terminal to the pseudonym storage module when the mobile terminal leaves the responsible area of the blockchain or the number of uploaded location points reaches the location point threshold, and no longer receives the information uploaded by the pseudonym until the next time the pseudonym is sent.

[0045] The pseudonym storage module marks the called pseudonym as deleted, refuses to send the pseudonym marked as deleted to the task assignment module, and removes the mark of the received pseudonym.

[0046] 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, and reduce the consumption of pseudonym storage and ensure the real-time performance of the trajectory position.

[0047] Preferably, the edge node further comprises a task processing module.

[0048] The data storage module constructs a Merkle tree and stores the received trajectory information in the Merkle tree.

[0049] The task processing module receives a task query instruction, calls the task information and trajectory information stored by the data storage module according to the task query instruction, generates task data according to the task information and trajectory information, the task data includes task information and task completion, sends the found task data back, and displays the task data.

[0050] By adopting the above approach, Merkle trees effectively reduce storage space and transmission costs, and can quickly and accurately capture data changes, thus effectively improving data security.

[0051] In summary, the present invention has the following beneficial effects:

[0052] 1. Privacy trajectories are obtained through local differential privacy technology and multiple probability extension mechanisms. The user's movement trajectory is fragmented through multiple blockchains, and a pseudonym mechanism is used to obtain the fragmented movement trajectory. Finally, the task data is stored through the blockchain to avoid data leakage by third-party platforms, effectively increasing the difficulty of data cracking and improving the security of privacy data. Attached Figure Description

[0053] Figure 1 This is an overall system block diagram of Embodiment 2 of this application.

[0054] Figure 2 This is a block diagram of the edge node in Embodiment 2 of this application.

[0055] Explanation of reference numerals in the attached figures:

[0056] 1. Edge Node; 11. Data Storage Module; 12. Pseudo-Name Storage Module; 13. Task Publishing Module; 14. Task Assignment Module; 15. Track Recording Module; 16. Task Processing Module; 2. Mobile Terminal. Detailed Implementation

[0057] Example 1: This application discloses a method for multiple real-time trajectory privacy protection, the specific steps of which are as follows:

[0058] S100. Create multiple blockchains, set up edge node 1 for each blockchain, divide the responsible area for each blockchain, and establish a pseudonym library storing pseudonyms.

[0059] S101. Set the location threshold and upload interval. The location threshold is set by staff based on the block size and the computing power of edge node 1, and can be any integer around 10. The upload interval is set by staff based on the task type. For example, the upload interval for short-distance food delivery can be set to about half a minute, while for long-distance ride-hailing services it can be set to 1-2 minutes.

[0060] S200: Receive task information, including task start point, task end point, and task objective. Upload the task information to edge node 1 according to the blockchain where the task information is located.

[0061] S201 and Edge Node 1 broadcast task information via blockchain.

[0062] S300, acquire the location information uploaded by the mobile terminal 2, and 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. According to the selected map system (such as Google Map, Baidu Map, etc.), mark the location information of the mobile terminal 2 as the starting point coordinate on the map system, mark the target location of the task information as the ending point coordinate, acquire the coordinate values of the starting point coordinate and the ending point coordinate on the map system, calculate the shortest path by a path algorithm (Dijkstra algorithm or A algorithm can be selected), and display the shortest path on the map system to obtain the path navigation information.

[0063] S301, the edge node 1 sends a pseudonym to the mobile terminal 2 in the responsible area of the blockchain, 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.

[0064] S400, after sending the pseudonym to the mobile terminal 2, every interval interval duration, the edge node 1 receives the location point information uploaded by the mobile terminal 2, and the edge node 1 associates the pseudonym with the responsible range of the blockchain.

[0065] S401, divide the edge area of the responsible range of the blockchain.

[0066] S402, receive the location point information uploaded by the mobile terminal 2 and record the number of times of uploading the location point.

[0067] S403, obtain the movement trajectory according to the location point information, use the local differential privacy technology to interfere with the location point information, and then extend the movement trajectory from the processed location point to obtain a movement trajectory with multiple branches.

[0068] S404, the edge node 1 divides the branch movement trajectory belonging to the responsible area of the blockchain into sub-movement trajectories, and takes all the sub-movement trajectories as privacy trajectories.

[0069] S500, when the mobile terminal 2 leaves the responsible area of the blockchain or the number of times of uploading the recorded location point reaches the location point threshold, receive the last location point information uploaded by the mobile terminal 2 and the trajectory information corresponding to the pseudonym.

[0070] S501, associate the location point information with the pseudonym, and determine whether the location point information is in the edge area of the responsible range of the blockchain through the pseudonym.

[0071] S502, if the location point information is in the edge area of the responsible range, and the last location point information uploaded by the received pseudonym is not in the edge area of the responsible range, cancel the counting of the location point information of the pseudonym, until the uploaded location point information is out of the edge area of the responsible range or the pseudonym is withdrawn.

[0072] S503, the edge node 1 removes the mark of the received pseudonym in the pseudonym library, and meanwhile the 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 track of the task participant, prevent link attacks, and reduce the storage consumption of the pseudonym and ensure the real-time performance of the track position.

[0073] S600, the edge node 1 constructs a Merkle tree in the blockchain, and the blockchain stores the information uploaded by the mobile terminal 2, and stores the information uploaded by the mobile terminal 2 in the Merkle tree.

[0074] S601, after the edge node 1 receives 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, and sends the searched task data back.

[0075] S700, the task completion information is sent to the mobile terminal 2 corresponding to the task data.

[0076] The implementation principle of the multi-real-time track privacy protection method of the embodiment of the application is that the edge computing technology is introduced through the blockchain, the edge node 1 receives and transmits task and user position data, the private track is obtained as the first track protection through the local differential privacy technology and the multi-probability extension mechanism, the user's motion track is fragmented through multiple blockchains, and the fragmented motion track is obtained as the second track protection through the pseudonym mechanism, and finally the task data is stored through the blockchain to avoid data leakage by a third-party platform, as the third track protection, which effectively increases the data cracking difficulty and improves the security of the private data.

[0077] Embodiment two, the embodiment of the application discloses a multi-real-time track privacy protection system, as shown in Figure 1 and Figure 2 The system includes a plurality of 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 assigning module 14, a track recording module 15, and a task processing module 16.

[0078] As shown in Figure 2As shown, the data storage module 11 stores the responsible area of the corresponding blockchain, the location point threshold, and the upload interval duration. The location point threshold is set by the staff according to the size of the block division 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 delivery can be set to about half a minute, and the long-distance car 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 a plurality of pseudonyms. The pseudonym storage module 12 marks the called pseudonym as deleted, refuses to send the pseudonym marked as deleted to the task assignment module 14, and the pseudonym storage module 12 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 reduce pseudonym storage consumption and ensure the real-time of trajectory location. The Merkle tree effectively reduces the storage space and transmission cost, and can quickly and accurately capture data changes, effectively improving data security.

[0079] As shown in Figure 2 The task publishing module 13 receives task information, the task information includes task starting point, task end point, task target, sends the task information to the corresponding edge node 1 according to the task information in the blockchain, and publishes the task information to the mobile terminal 2 through the blockchain broadcast. The task assignment module 14 receives the location 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 12, and sends the pseudonym and the path navigation information to the mobile terminal 2. The task assignment module 14 receives the location point information uploaded by the mobile terminal 2 every interval upload interval duration, associates the pseudonym with the responsible range of the blockchain. According to the selected map system (such as Google map, Baidu map, etc.), the location information of the mobile terminal 2 is marked as the starting point coordinate on the map system, and the target location of the task information is marked as the end point coordinate. The coordinate values of the starting point coordinate and the end point coordinate are obtained on the map system, and the shortest path is calculated by a path algorithm (Dijkstra algorithm or A algorithm can be selected). The shortest path is displayed on the map system to obtain the path navigation information.

[0080] As shown in 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 times of uploading the location point, 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, then extends the movement trajectory from the processed location point, obtains the movement trajectory with multiple branches, divides the branch movement trajectory belonging to the responsible area of the blockchain into a sub-movement trajectory, and takes all the sub-movement trajectories as a private trajectory. The private 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 times of uploading the recorded location point 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. The trajectory 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 times of uploading the recorded location point reaches the location point threshold, and no longer receives the information uploaded by the pseudonym until the next time the pseudonym is sent. The local differential privacy technology can protect the privacy of data during data collection, and obtain a sub-movement trajectory after randomly extending the movement trajectory. The sub-movement trajectory can play a confusing role, further improving the data security.

[0081] As shown in Figure 2 The trajectory recording module 15 associates the location point information with the pseudonym, judges whether the location point information is in the edge area of the responsible range of the blockchain through the pseudonym, cancels the counting of the location point information of 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, and until the uploaded location point information is out of 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.

[0082] As shown in Figure 2 The task processing module 16 calls the task information and trajectory information stored in the data storage module 11, generates task data according to the task information and trajectory information, and displays the task data. When the task processing module 16 receives a 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. When the task processing module 16 receives the task completion information, it sends the task completion information to the mobile terminal 2.

[0083] The embodiments of the specific implementation are the preferred embodiments of the application, not limited to the protection scope of the application, so that: any equivalent changes made according to the structure, shape, principle of the application should be covered within the protection scope of the application.

Claims

1. A method for multiple real-time trajectory privacy protection, characterized in that, The method comprises the following steps: Creating multiple blockchains, setting edge nodes (1) for each blockchain, dividing responsible areas for each blockchain, and establishing a pseudonym library storing pseudonyms; Setting a location point threshold and an upload interval; Receiving task information, which includes a task starting point, a task ending point, and a task target, uploading the task information to the edge node (1) according to the blockchain where the task information is located; The edge node (1) broadcasts and publishes the task information through the blockchain; The edge node (1) obtains the location information uploaded by the mobile terminal (2), 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); In the responsible area of the blockchain, the edge node (1) sends a pseudonym to the mobile terminal (2), and the edge node (1) receives the location point information uploaded by the mobile terminal (2) through the pseudonym and records the number of times of uploading the location point information every interval of the upload interval; The edge node (1) associates the pseudonym with the responsible area of the blockchain; Dividing the range edge area of the responsible area of the blockchain; Obtaining the movement trajectory according to the location point information, processing the movement trajectory of the mobile terminal (2) using the local differential privacy technology and the multiple probability extension mechanism to obtain a privacy trajectory; When the mobile terminal (2) leaves the responsible area of the blockchain or the number of times of uploading the recorded location point reaches the location point threshold, receiving the last uploaded location point information of the mobile terminal (2); Associating the location point information with the pseudonym to determine whether the location point information is in the range edge area of the blockchain through the pseudonym; If the location point information is in the range edge area and the last uploaded location point information of the pseudonym received is not in the range edge area, canceling the counting of the location point information of the pseudonym until the uploaded location point information leaves the responsible range edge area or the pseudonym is withdrawn.

2. The method of claim 1, wherein, The processing of the movement trajectory of the mobile terminal (2) using the local differential privacy technology and the multiple probability extension mechanism to obtain a privacy trajectory comprises: Using the local differential privacy technology to interfere with the location point information, and then extending the movement trajectory from the processed location point to obtain a movement trajectory with multiple branches; Dividing the branch movement trajectory belonging to the responsible area of the blockchain into sub-movement trajectories, and taking all the sub-movement trajectories as the privacy trajectory.

3. The method of claim 1, wherein, After the edge node (1) sends the pseudonym to the mobile terminal (2) in the responsible area of the blockchain: The edge node (1) marks the sent pseudonym in the pseudonym library.

4. The method of claim 1, wherein, Further comprising the following steps: The edge node (1) removes the mark of the pseudonym in the pseudonym library, and no longer receives the information uploaded by the pseudonym until the next time the pseudonym is sent.

5. The method of claim 1, wherein, Further comprising the following steps: 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 a task query instruction, the edge node (1) searches for corresponding task data in the blockchain, the task data including task information and task completion information, and sends the task completion information to the mobile terminal (2) corresponding to the task data.

6. A multiple real-time trajectory privacy protection system, characterized in that: The system comprises a plurality of edge nodes (1) and mobile terminals (2), each edge node (1) comprises a blockchain, and each edge node (1) comprises a data storage module (11), a pseudonym storage module (12), a task publishing module (13), a task assigning module (14) and a trajectory recording module (15); The data storage module (11) stores the responsible area of the corresponding blockchain, a location point threshold and an uploading interval; The pseudonym storage module (12) stores a plurality of pseudonyms; The task publishing module (13) receives task information, the task information comprises a task starting point, a task ending point and a task target, sends the task information to the 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 assigning module (14) receives the location 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 (12), sends the pseudonym and the path navigation information to the mobile terminal (2), and the edge node (1) receives the location point information uploaded by the mobile terminal (2) every interval uploading interval, and associates the pseudonym with the responsible area of the blockchain; The trajectory recording module (15) receives the location point information uploaded by the mobile terminal (2) through the pseudonym, records the number of times of uploading the location point, processes the movement trajectory of the mobile terminal (2) by using a local differential privacy technology and a multiple probability extension mechanism, obtains a private trajectory, associates the private trajectory with the mobile terminal (2) and sends the private trajectory to the data storage module (11), receives the last location point information uploaded by the mobile terminal (2) when the mobile terminal (2) leaves the responsible area of the blockchain or the number of times of uploading the recorded location point information reaches the location point threshold, and sends the trajectory information to the data storage module (11); the trajectory recording module (15) associates the location point information with the pseudonym, judges whether the location point information is in the range edge area of the blockchain through the pseudonym, cancels the counting of the location point information of the pseudonym if the location point information is in the range edge area and the last location point information uploaded by the pseudonym received is not in the range edge area, and recovers the pseudonym until the uploaded location point information leaves the range edge area.

7. The multiple real-time trajectory privacy protection system of claim 6, wherein: The trajectory recording module (15) uses the local differential privacy technology to interfere with the location point information, extends the movement trajectory from the processed location point, obtains a movement trajectory with multiple branches, divides the branch movement trajectory belonging to the responsible area of the blockchain into a sub-movement trajectory, and takes all the sub-movement trajectories as the private trajectory.

8. The multiple real-time trajectory privacy protection system of claim 6, wherein: After the task assigning module (14) calls the pseudonym of the pseudonym storage module (12), the pseudonym storage module (12) marks the called pseudonym.

9. The multiple real-time trajectory privacy protection system according to claim 6, wherein: The trajectory 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 times of uploading the recorded location point reaches the location point threshold. The pseudonym storage module (12) removes the mark of the received pseudonym.

10. The multiple real-time trajectory privacy protection system of claim 6, wherein: The edge node (1) further comprises a task processing module (16); 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 information and the trajectory information stored by the data storage module (11) according to the task query instruction, generates task data according to the task information and the trajectory information, the task data includes task information and task completion, sends the found task data back, and displays the task data.

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