A method and device for embedding watermark information into real-time trajectory data

Abstract

The present application relates to the field of geographic information security technology, and specifically to a method and apparatus for embedding watermark information in real-time trajectory data. The method comprises splitting the trajectory data acquired in real time according to a preset data extraction method to obtain at least one sub-trajectory segment; converting the spatiotemporal trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data according to the spatial and temporal attributes of the sub-trajectory segment, wherein the time-frequency matrix data includes multiple frequency values; determining at least one frequency peak from the frequency values ​​corresponding to the sub-trajectory segment; determining the timestamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index, and calculating the watermark index of the timestamp; performing a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index; and performing an inverse short-time Fourier transform on the frequency value after the parity operation and the original phase of the frequency value to obtain the trajectory data embedded with the watermark information.

Description

Technical Field

[0001] The present invention relates to the field of geographic information security technology, and in particular to a method and device for embedding watermark information into real-time trajectory data. Background Art

[0002] With the rapid development of internet technology and mobile positioning technology, more and more location-based services have entered people's lives. User trajectory data is often stored, analyzed, published, and mined in the form of trajectory sequences supplemented with location information. It is widely used in urban planning, transportation, behavior analysis, and other fields, playing a significant role in modern life, production, scientific research, and business development. However, because trajectory data contains a large amount of user privacy information, it is easily stolen during transmission and sharing. The resulting copyright protection issues have seriously hindered the application and research of trajectory data.

[0003] Existing classic digital watermarking technologies are designed for offline trajectory data. This involves embedding watermark information after the data has been collected and processed. However, these algorithms fail to provide security during the trajectory data collection and upload process, making data theft highly likely. Therefore, there is an urgent need to research security algorithms for real-time trajectory data to protect copyright during the original trajectory data collection process.

[0004] Although the existing research on digital watermarking algorithms for geographic data has achieved fruitful results, there is currently no algorithm that can apply digital watermarks to real-time trajectory data, which cannot achieve the security effect of protecting the data from being destroyed throughout the entire process. Summary of the Invention

[0005] The present invention provides a method for embedding watermark information into real-time trajectory data, which can be used to solve related problems in the prior art. The method specifically includes:

[0006] Splitting the trajectory data acquired in real time according to a preset data extraction method to obtain at least one sub-trajectory segment;

[0007] According to the spatial attributes and temporal attributes of the sub-trajectory segment, the spatiotemporal trajectory data corresponding to the sub-trajectory segment is converted into time-frequency matrix data, wherein the time-frequency matrix data includes a plurality of frequency values;

[0008] determining at least one frequency peak from the frequency values ​​corresponding to the sub-trajectory segments;

[0009] According to the correspondence between the frequency peak and the time index, a timestamp corresponding to the frequency peak is determined, and a watermark index of the timestamp is calculated;

[0010] performing a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index;

[0011] The frequency value after the parity operation and the original phase of the frequency value are used to perform inverse short-time Fourier transform to obtain the trajectory data embedded with the watermark information.

[0012] Specifically, determining at least one frequency peak from the frequency values ​​corresponding to the sub-trajectory segments includes:

[0013] Calculating the amplitude spectrum of each data in the time-frequency matrix data;

[0014] The frequency value of the amplitude spectrum within a preset range is used as the frequency peak.

[0015] Furthermore, before determining the timestamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index and calculating the watermark index of the timestamp, the method further includes:

[0016] A random sequence is generated using a two-dimensional mapping method, and an XOR operation is performed on the random sequence and the image binary sequence to complete the encryption operation of the acquired copyright information.

[0017] Specifically, performing a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index includes:

[0018] When the value of the watermark information corresponding to the watermark index is 0, the frequency value corresponding to the watermark index is adjusted to an even number;

[0019] When the value of the watermark information corresponding to the watermark index is 1, the frequency value corresponding to the watermark index is adjusted to an odd number.

[0020] Specifically, the real-time acquired trajectory data is split according to a preset data extraction method to obtain at least one sub-trajectory segment, including:

[0021] The data at the first preset position in the split current sub-track segment overlaps with part of the data in the previous sub-track segment;

[0022] The data at the second preset position in the split current sub-trajectory segment overlaps with part of the data in the subsequent sub-trajectory segment;

[0023] The first preset position is before the second preset position.

[0024] Specifically, calculating the watermark index of the timestamp includes:

[0025] Use the hash function to calculate the watermark index for the timestamp. The formula is as follows:

[0026]

[0027] is the time index, is the hash value of the time index, The watermark index calculated based on the time index.

[0028] An embodiment of the present invention provides a device for embedding watermark information into real-time trajectory data, the device comprising:

[0029] A splitting module is used to split the trajectory data obtained in real time according to a preset data extraction method to obtain at least one sub-trajectory segment;

[0030] a conversion module, configured to convert the spatiotemporal trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data according to the spatial and temporal attributes of the sub-trajectory segment, wherein the time-frequency matrix data includes a plurality of frequency values;

[0031] a first determining module, configured to determine at least one frequency peak from the frequency values ​​corresponding to the sub-trajectory segments;

[0032] A second determining module is configured to determine a timestamp corresponding to the frequency peak according to a correspondence between the frequency peak and the time index, and calculate a watermark index of the timestamp;

[0033] an operation module, configured to perform a parity operation on a frequency value corresponding to the watermark index based on a value of the watermark information corresponding to the watermark index;

[0034] The transformation module is used to perform inverse short-time Fourier transform on the frequency value after the parity operation and the original phase of the frequency value to obtain trajectory data embedded with watermark information.

[0035] Specifically, the first determining module is specifically configured to:

[0036] Calculating the amplitude spectrum of each data in the time-frequency matrix data;

[0037] The frequency value of the amplitude spectrum within a preset range is used as the frequency peak.

[0038] Furthermore, the device further comprises:

[0039] The encryption module is used to generate a random sequence using a two-dimensional mapping method, perform an XOR operation on the random sequence and the image binary sequence, and complete the encryption operation of the acquired copyright information.

[0040] An embodiment of the present invention further provides an electronic device, characterized in that the electronic device includes a processor, a memory, and a program or instruction stored in the memory and executable on the processor, wherein the program or instruction is executed by the processor to perform the steps of the method for embedding watermark information in real-time trajectory data.

[0041] The method provided by the embodiments of the present invention addresses potential theft and copyright verification issues during the real-time collection, transmission, and sharing of trajectory data, as well as the real-time data collection and transmission requirements. Copyright information can be embedded in real time during data collection, and blind detection and extraction of watermark information can be achieved. The proposed algorithm has high robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flow chart of a method for embedding watermark information into real-time trajectory data provided by an embodiment of the present invention;

[0043] Figure 2 A schematic diagram of the structure of a device for embedding watermark information into real-time trajectory data provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0045] In the description of this application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0046] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, if the term "plurality" appears, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0047] Trajectory data is a time-series data consisting of discrete points. It possesses both spatial and temporal attributes, making it a type of geographic big data. Therefore, digital watermarking algorithms for vector geographic data can provide a reference for digital watermarking algorithms for trajectory data. Existing digital watermarking algorithms for vector geographic data can be divided into three categories based on the embedding domain: geometric domain, frequency domain, and attribute information. The geometric domain is mostly used for line and surface data. Trajectory data, however, is prone to geometric feature loss due to unique operations (such as trajectory data cleaning). Therefore, these algorithms are less robust when applied to trajectory data. Attribute information in trajectory data generally involves user privacy, so embedding copyright information using attribute information is also undesirable. Frequency domain algorithms, however, are effective for trajectory data due to their high concealment and robustness. To address these issues, the methods of the present invention are proposed.

[0048] The embodiment of the present invention provides a method for embedding watermark information into real-time trajectory data. Figure 1 As shown, the specific process is as follows:

[0049] Step 11: Split the trajectory data acquired in real time according to a preset data extraction method to obtain at least one sub-trajectory segment. The specific process of this step is as follows:

[0050] This step requires that the data at the first preset position in the split current sub-track segment overlap with part of the data in the previous sub-track segment;

[0051] The data at the second preset position in the split current sub-trajectory segment overlaps with part of the data in the subsequent sub-trajectory segment;

[0052] The first preset position is before the second preset position. That is, the data at the front of the current sub-track segment should overlap with the data at the back of the previous sub-track segment; and the data at the back of the current sub-track segment should overlap with the data at the front of the next sub-track segment.

[0053] The specific explanation of this step is as follows:

[0054] The trajectory data to be collected by this method can be any trajectory data, such as GPS data, sensor data, lidar data, etc.

[0055] First, the trajectory data is segmented according to the preset data extraction method. The preset data extraction method can be to segment the real-time trajectory data according to the set time threshold. For example, trajectory data collection is usually sampled at 0.1 seconds or 50 milliseconds. Therefore, this method segments the real-time trajectory data with a time threshold of 5 seconds to generate sub-trajectories. .in, Representative Segment track segment, is the total number of sub-trajectory segments. That is, every time data is collected for 5 seconds, the data segment is decomposed into a sub-trajectory segment, and the sub-trajectory segment is subsequently processed.

[0056] At the same time, in order to resist the time attack of trajectory data, overlapping windows are used in segmentation to ensure that each window contains the time information of the previous and next parts, thereby enhancing the continuity of time.

[0057] Step 12: Convert the spatiotemporal trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data based on the spatial and temporal attributes of the sub-trajectory segment. The time-frequency matrix data includes multiple frequency values. This step specifically includes:

[0058] Perform time-frequency analysis on the data of each sub-trajectory segment, that is, use Short Time Fourier Transform (STFT) to transform the spatiotemporal trajectory data into a time-frequency matrix data, where is the frequency value, is time, and the STFT conversion formula is shown in formula (1):

[0059] Formula (1)

[0060] Choose an appropriate window function To process real-time spectrum signals, this method uses a Hamming window to control spectrum leakage.

[0061] Step 13: Determine at least one frequency peak from the frequency values ​​corresponding to the sub-trace segments. This step specifically includes:

[0062] Calculate the amplitude spectrum of each data in the time-frequency matrix data; and use the frequency value of the amplitude spectrum within a preset range as the frequency peak. For example:

[0063] First, extract the features of the sub-trajectory segment and calculate the amplitude spectrum of the STFT result of the sub-trajectory segment ,The absolute value is used here to remove the phase information and only focus on the ,energy distribution of the signal, which simplifies the subsequent processing and facilitates ,embedding the watermark information into the amplitude without interfering ,with the phase.

[0064] For non-stationary signals like trajectory data (i.e., signals whose characteristics change over time), different time periods may have different frequency components. This can result in multiple frequency peaks in the spectrum within the same time window. Therefore, dynamic frequency bin selection is necessary. This method is designed for real-time trajectory data, so it requires an adaptive algorithm to dynamically select frequency bins for each signal segment based on real-time data analysis.

[0065] In this solution, peak detection can be applied to identify high-energy frequencies in the signal. By setting an amplitude threshold, peaks below a certain energy level are filtered out, and only the main peaks are retained. The peaks that meet the conditions and their corresponding frequencies are recorded to form a frequency list. , the frequency list includes at least one frequency peak , where 1≤i≤n.

[0066] Step 14: Determine the timestamp corresponding to the frequency peak based on the correspondence between the frequency peak and the time index, and calculate the watermark index of the timestamp. This step specifically includes:

[0067] For each peak , identifying the specific time index corresponding to this peak in the spectrum , and record the corresponding timestamp, and use the hash function to calculate the watermark index for the timestamp The calculation formula is formula (2):

[0068] Formula (2)

[0069] in, is the time index, is a hash function, is the hash value of the time index, The watermark index calculated based on the time index.

[0070] Step 15: Based on the value of the watermark information corresponding to the watermark index, determine the frequency value corresponding to the watermark index and perform a parity operation. The specific process of this step is as follows:

[0071] When the value of the watermark information corresponding to the watermark index is 0, the frequency value corresponding to the watermark index is adjusted to an even number; when the value of the watermark information corresponding to the watermark index is 1, the frequency value corresponding to the watermark index is adjusted to an odd number. For example:

[0072] Check The corresponding watermark information and the time index are checked at the same time The corresponding peak value of the time-frequency matrix data If the watermark information is 0, adjust the time index The corresponding time-frequency matrix data peak is an even number; if the watermark information is 1, the time-frequency matrix data peak corresponding to the adjusted time index is an odd number.

[0073] Step 16: Perform an inverse short-time Fourier transform on the frequency value after the parity operation and the original phase of the frequency value to obtain the trajectory data embedded with the watermark information. Specifically, the following steps are performed:

[0074] Repeat the above steps until the frequency list All frequency values ​​in are embedded with watermark information. The adjusted amplitude peak and original phase are used to perform inverse STFT to reconstruct the watermarked signal, and finally the watermarked sub-track segment data is obtained.

[0075] Repeat the above steps until all sub-trajectory segments are collected. The obtained trajectory dataset is the data set with embedded watermark information. This process can be applied not only to trajectory data collected and transmitted in real time, but also to trajectory data processed offline.

[0076] Specifically, before determining the timestamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index and calculating the watermark index of the timestamp, the method further includes:

[0077] A random sequence is generated using a two-dimensional mapping method, and the random sequence is XORed with the image binary sequence to complete the encryption of the acquired copyright information. The specific process is as follows:

[0078] Copyright information can be any image, string or other copyright information. This method takes the copyright information as Binary copyright image, arrange the image into a one-dimensional binary sequence by row .

[0079] Copyright information encryption can use any algorithm. This method uses a two-dimensional Henon map to generate a random sequence, and performs an XOR operation on the random sequence and the image binary sequence to complete the encryption of the copyright information.

[0080] The binary ciphertext obtained after encryption is the encrypted binary copyright information .

[0081] The method provided by the embodiments of the present invention addresses potential theft and copyright verification issues during the real-time collection, transmission, and sharing of trajectory data, as well as the real-time data collection and transmission requirements. Copyright information can be embedded in real time during data collection, and blind detection and extraction of watermark information can be achieved. The proposed algorithm has high robustness.

[0082] In the embodiment of the present invention, a method of time threshold overlapping windows is used to segment the trajectory data during the data acquisition process. The segmented trajectory data is converted into the frequency domain using short-time Fourier transform. A list of peaks in the spectrum and their corresponding time indexes are extracted based on the spectrum distribution. The time index is hashed to generate a watermark index. Finally, the watermark information is embedded into the peak through parity quantization.

[0083] This method fully considers the characteristics of the trajectory data collection process, combines the characteristics of the trajectory data itself, and adopts overlapping window segmentation combined with short-time Fourier transform to effectively ensure the concealment of watermark information embedding. At the same time, it enables this method to embed copyright information in real time during the real-time collection of trajectory data. In addition, multi-spectrum repeated embedding not only realizes a large-capacity watermark algorithm, but also ensures robustness against common attacks.

[0084] like Figure 2 As shown, an embodiment of the present invention provides a device for embedding watermark information into real-time trajectory data, the device comprising:

[0085] A splitting module 21 is used to split the trajectory data acquired in real time according to a preset data extraction method to obtain at least one sub-trajectory segment;

[0086] a conversion module 22 for converting the spatiotemporal trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data according to the spatial and temporal attributes of the sub-trajectory segment, wherein the time-frequency matrix data includes a plurality of frequency values;

[0087] a first determining module 23, configured to determine at least one frequency peak from the frequency values ​​corresponding to the sub-trajectory segments;

[0088] A second determining module 24 is configured to determine a timestamp corresponding to the frequency peak according to a correspondence between the frequency peak and the time index, and calculate a watermark index of the timestamp;

[0089] an operation module 25, configured to perform a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index;

[0090] The transformation module 26 is configured to perform an inverse short-time Fourier transform on the frequency value after the parity operation and the original phase of the frequency value to obtain the trajectory data embedded with the watermark information.

[0091] The first determining module 23 is specifically configured to:

[0092] Calculating the amplitude spectrum of each data in the time-frequency matrix data;

[0093] The frequency value of the amplitude spectrum within a preset range is used as the frequency peak.

[0094] The device further comprises:

[0095] The encryption module 27 is used to generate a random sequence using a two-dimensional mapping method, perform an XOR operation on the random sequence and the image binary sequence, and complete the encryption operation of the acquired copyright information.

[0096] An embodiment of the present invention further provides an electronic device, characterized in that the electronic device includes a processor, a memory, and a program or instruction stored in the memory and executable on the processor, wherein the program or instruction is executed by the processor to perform any one of the steps of the above-mentioned method for embedding watermark information in real-time trajectory data.

[0097] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connected," "fixed," etc., should be interpreted broadly. For example, these terms may refer to fixed connections, removable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediary; and internal communication between two components or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0098] In this application, unless otherwise expressly specified or limited, if a first feature is described as being "above" or "below" a second feature, or similar descriptions, this may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is described as being "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is described as being "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0099] It should be noted that if an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may also be a central element. If an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method. The various technical features of the embodiments described above can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for embedding watermark information into real-time trajectory data, characterized in that: The method comprises: Splitting the real-time acquired geographic trajectory data according to a preset data extraction method to obtain at least one sub-trajectory segment; According to the spatial attributes and temporal attributes of the sub-trajectory segment, the spatiotemporal geographic trajectory data corresponding to the sub-trajectory segment is converted into time-frequency matrix data, wherein the time-frequency matrix data includes a plurality of frequency values; Calculating the amplitude spectrum of each data in the time-frequency matrix data; taking the frequency value of the amplitude spectrum within a preset range as the frequency peak; According to the correspondence between the frequency peak and the time index, a timestamp corresponding to the frequency peak is determined, and a watermark index of the timestamp is calculated; performing a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index; The frequency value after the parity operation is used and the original phase of the frequency value are used to perform inverse short-time Fourier transform to obtain geographic trajectory data embedded with watermark information.

2. The method according to claim 1, wherein Before determining the timestamp corresponding to the frequency peak according to the correspondence between the frequency peak and the time index and calculating the watermark index of the timestamp, the method further includes: A random sequence is generated using a two-dimensional mapping method, and an XOR operation is performed on the random sequence and the image binary sequence to complete the encryption operation of the acquired copyright information.

3. The method according to claim 1, wherein The performing a parity operation on the frequency value corresponding to the watermark index based on the value of the watermark information corresponding to the watermark index includes: When the value of the watermark information corresponding to the watermark index is 0, the frequency value corresponding to the watermark index is adjusted to an even number; When the value of the watermark information corresponding to the watermark index is 1, the frequency value corresponding to the watermark index is adjusted to an odd number.

4. The method according to claim 1, wherein The method of splitting the real-time acquired geographic trajectory data according to a preset data extraction method to obtain at least one sub-trajectory segment includes: The data at the first preset position in the split current sub-track segment overlaps with part of the data in the previous sub-track segment; The data at the second preset position in the split current sub-track segment overlaps with part of the data in the subsequent sub-track segment; The first preset position is before the second preset position.

5. The method according to claim 1, wherein The calculating of the watermark index of the timestamp includes: Use the hash function to calculate the watermark index for the timestamp. The formula is as follows: W index =Hash(t peak ) t peak is the time index, Hash(t peak ) is the hash value of the time index, W index The watermark index calculated based on the time index.

6. A device for embedding watermark information into real-time trajectory data, characterized in that: The device comprises: A splitting module, configured to split the real-time acquired geographic trajectory data according to a preset data extraction method to obtain at least one sub-trajectory segment; a conversion module, configured to convert the spatiotemporal geographic trajectory data corresponding to the sub-trajectory segment into time-frequency matrix data according to the spatial attributes and temporal attributes of the sub-trajectory segment, wherein the time-frequency matrix data includes a plurality of frequency values; A first determining module is configured to calculate the amplitude spectrum of each data in the time-frequency matrix data; and take the frequency value of the amplitude spectrum within a preset range as the frequency peak value; A second determining module is configured to determine a timestamp corresponding to the frequency peak according to a correspondence between the frequency peak and the time index, and calculate a watermark index of the timestamp; an operation module, configured to perform a parity operation on a frequency value corresponding to the watermark index based on a value of the watermark information corresponding to the watermark index; The transformation module is used to perform inverse short-time Fourier transform on the frequency value after the parity operation and the original phase of the frequency value to obtain geographic trajectory data embedded with watermark information.

7. The device according to claim 6, characterized in that The device further comprises: The encryption module is used to generate a random sequence using a two-dimensional mapping method, perform an XOR operation on the random sequence and the image binary sequence, and complete the encryption operation of the acquired copyright information.

8. An electronic device, characterized in that: The electronic device includes a processor, a memory, and a program or instruction stored in the memory and executable on the processor. The program or instruction is used by the processor to execute the steps of the method for embedding watermark information in real-time trajectory data according to any one of claims 1 to 5.

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