Ship navigation data security evidence storage method and system

Abstract

The invention relates to the field of digital information transmission, in particular to a ship navigation data security evidence storage method and system. The method comprises the steps that real-time navigation state data of a ship are collected and preprocessed; calculating a navigation maneuverability index reflecting the current maneuverability intensity of the ship by using the preprocessed real-time navigation state data of the ship; based on the navigation maneuverability index, the length of a sliding window of a compression algorithm is determined through a preset reverse attenuation model, and the length of the sliding window is in negative correlation with the navigation maneuverability index; and configuring the length of the sliding window as a search range of a compression encoder, compressing and encrypting the real-time navigation state data of the ship to obtain an evidence storage data packet, and writing the evidence storage data packet into a shipborne storage medium. According to the method, the compression strategy is dynamically adjusted, the storage space utilization rate and the computing resource consumption are effectively balanced while real-time data storage is guaranteed, and the transmission and storage efficiency of the ship navigation data is improved.

Description

Technical Field

[0001] This invention relates to the field of digital information transmission, and more specifically to a method and system for securely storing ship navigation data. Background Technology

[0002] In modern intelligent shipping systems, ship navigation data recorders play a crucial role similar to aircraft black boxes, responsible for recording real-time heterogeneous data from multiple sources, such as the ship's position, speed, heading, and rudder angle. This data is not only the core basis for maritime accident investigations but also an important foundation for shipping efficiency analysis and remote monitoring. Since ocean-going vessels mainly rely on maritime satellite links for communication with shore during navigation, and satellite communication bandwidth is extremely limited and expensive, efficient data compression is a necessary means to reduce operating costs.

[0003] Currently, the LZ77 algorithm is widely used in the industry for lossless compression of ship data. This algorithm uses a sliding window mechanism to find duplicate strings in historical data to achieve compression. However, existing application solutions usually use a fixed-length sliding window, which cannot adapt to the complex and ever-changing navigation conditions of ships. During the stable period of long-term straight-line speed maintenance of ships, the fixed and small sliding window cannot cover long-term repetitive data, resulting in the compression potential not being fully explored and bandwidth being wasted.

[0004] Conversely, during complex maneuvers such as when ships enter or leave port or during emergency collision avoidance, data changes drastically and historical relevance decays rapidly. If a large fixed window is maintained at this time, the algorithm will conduct ineffective searches in a large amount of irrelevant historical data, which will not only fail to improve the compression rate, but will also consume a lot of computing resources, resulting in data writing delays. In extreme accident conditions such as power outages or collisions, such delays may cause data at critical moments to be permanently lost because it cannot be stored in time. Summary of the Invention

[0005] To address the problem that existing ship data storage technologies, particularly those using fixed sliding windows, cannot balance the high compression rate during stable periods with the real-time requirements during maneuvering periods, leading to wasted storage resources and data loss, this invention provides a method and system for securely storing ship navigation data.

[0006] In a first aspect, the present invention provides a method for securely storing ship navigation data, employing the following technical solution: Real-time navigation status data of the vessel is collected, including the vessel's maneuverability parameters and positioning parameters. The positioning parameters include the vessel's latitude and longitude information, and the maneuverability parameters include the vessel's heading, ground speed, and actual rudder angle. The real-time navigation status data is preprocessed to obtain a time-series data stream containing timestamps and the vessel's latitude and longitude information. Using the time-series data stream, by comprehensively considering changes in the vessel's heading, speed, and rudder angle deviation, a navigation maneuverability index reflecting the current degree of maneuverability is obtained. Based on the navigation maneuverability index, the length of the sliding window of the LZ77 compression algorithm is determined using a preset reverse attenuation model. The length of the sliding window satisfies the following relationship:

[0007] in, Let be the length of the sliding window at time t. For the floor function, This is the preset minimum length of the sliding window. This is the preset maximum length of the sliding window. This is the attenuation sensitivity coefficient. It is a natural constant. The navigation maneuverability index at time t; The length of the sliding window is input into the compression encoder as a configuration parameter to compress the real-time navigation status data to obtain a binary data stream. The binary data stream is then encrypted and its integrity is verified to obtain a certificate data packet, which is then written to the shipboard storage medium.

[0008] This invention collects real-time navigation status data of ships and calculates navigation maneuverability index, enabling real-time assessment of the ship's motion status and providing accurate quantitative basis for subsequent operations. At the same time, by adaptively determining the length of the sliding window, the length of the sliding window can be increased to improve compression efficiency when the ship is sailing smoothly, and decreased to reduce computational load when the ship is maneuvering violently. Thus, the optimal balance between compression efficiency and real-time performance is achieved while ensuring data security and evidence preservation.

[0009] Furthermore, the navigation maneuverability index satisfies the following relationship:

[0010] in, Let be the navigation maneuverability index at time t. Indicates the change in the ship's heading. Indicates changes in a ship's speed. This indicates that the ship's rudder angle has deviated. , , These are the weighting coefficients for the changes in bow direction, speed, and rudder angle deviation, respectively. Let be the shortest angular distance from the bow at time t. For the sampling time step, and These are the ground speeds at times t and t-1, respectively. The actual rudder angle at time t. This is the reference rudder angle.

[0011] This invention eliminates logical ambiguity caused by data mutations by unifying the dimensions of each physical quantity to square terms and introducing the shortest angular distance from the bow, thus ensuring the objectivity and physical authenticity of the evaluation indicators.

[0012] Furthermore, the shortest angular distance from the bow satisfies the following relationship:

[0013] in, and These are the ship's headings at times t and t-1, respectively, with values ​​ranging from 0 degrees to 360 degrees.

[0014] Furthermore, the preprocessing includes: aligning and denoising the real-time navigation status data.

[0015] Furthermore, the compression process includes: configuring the length of the sliding window as the search range of the compression encoder; when encoding the real-time navigation status data, by limiting the offset of the logical search pointer of the history buffer of the compression encoder, searching only within the search range for strings that match the real-time navigation status data and encoding them to generate the binary data stream.

[0016] This invention maps the length of the sliding window to the search range of the compression encoder, which can force a reduction in the search range when the data correlation decays rapidly due to violent ship maneuvers. This effectively reduces the matching operations of invalid strings, prevents computational congestion, and ensures millisecond-level response capability on low-power shipboard hardware.

[0017] Furthermore, the weighting coefficients for changes in heading, speed, and rudder angle deviation are obtained through statistical analysis experiments based on the ship's historical navigation data.

[0018] Furthermore, the encryption process and integrity verification include: performing cryptographic transformation on the binary data stream to obtain ciphertext data blocks; calculating digital digests based on the ciphertext data blocks; and encapsulating the ciphertext data blocks and the digital digests to obtain the evidence storage data packet.

[0019] This invention employs a strategy that combines encrypted data blocks with digital digests to ensure the confidentiality and integrity of real-time navigation status data. Specifically, cryptographic transformations effectively protect commercially sensitive information such as ship position and route; while calculating digital digests can quickly screen for tampering or loss of data during storage or transmission.

[0020] Furthermore, the attenuation sensitivity coefficient is obtained through response calibration experiments based on the ship's standard steering conditions.

[0021] Secondly, this invention provides a secure data storage system for ship navigation, employing the following technical solution: A ship navigation data security storage system includes a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the above-mentioned ship navigation data security storage method is implemented.

[0022] By adopting the above technical solution, the above-mentioned method for securely storing ship navigation data generates a computer program and stores it in a memory, which is then loaded and executed by a processor. This allows for the creation of a terminal device based on the memory and processor, making it convenient to use.

[0023] The present invention has the following technical effects: The ship navigation data security storage system provided by this invention addresses the technical problem that ocean-going vessels are highly dependent on satellite links and have limited bandwidth. By introducing a navigation maneuverability index, it breaks through the limitations of traditional fixed window compression. During the stable navigation period, such as straight sailing and anchoring, which accounts for the majority of the time, the length of the sliding window is increased to ensure compression efficiency. This not only significantly saves satellite communication costs but also effectively extends the data retention period of the ship's onboard storage medium. During periods of high incidence of accidents such as collisions, groundings, and emergency avoidance, data streams burst instantly and have extremely low correlation. This invention uses a preset reverse attenuation model to rapidly shrink the sliding window within milliseconds, avoiding the search for a large amount of invalid historical data. This ensures that all critical navigation data can be written in a timely manner in the final critical moment before the ship loses power or is damaged, thus preserving information for accident investigation.

[0024] Unlike simple log recording, this invention deeply integrates dynamic compression with cryptographic technology. By synchronously encapsulating ciphertext data blocks and digital digests, it constructs a complete chain of evidence, meeting the requirements of modern intelligent shipping for data integrity and legal compliance. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method for securely storing ship navigation data provided in an embodiment of the present invention; Figure 2This is a comparative analysis chart of ship navigation status and navigation maneuverability index provided in an embodiment of the present invention; Figure 3 This is a sliding window change diagram provided in an embodiment of the present invention; Figure 4 This is a comparison chart of data storage evidence provided in an embodiment of the present invention. Detailed Implementation

[0026] This invention provides a method for securely storing ship navigation data, referring to... Figure 1 This includes steps S1-S4: S1: Collect and preprocess real-time navigation status data of the ship to obtain a time-series data stream containing timestamps and the ship's latitude and longitude information.

[0027] 1. Multi-source data acquisition and definition Following the IEC 61162 standard protocol, real-time navigation status data of the vessel is collected through the shipboard data interface unit, including: timestamps, maneuverability parameters, and positioning parameters. The positioning parameters are the vessel's latitude and longitude, and the maneuverability parameters include the bow direction. Ground speed Actual rudder angle ; For ships at time The navigation direction ranges from 0° to 360°. For ships at time ground speed, For the rudder blade at all times The deflection angle is negative for left rudder and positive for right rudder.

[0028] 2. Pretreatment (1) Set the minimum time interval threshold. In this embodiment, it is set to 0.01 seconds. If the difference between the current timestamp and the previous timestamp is less than the minimum time interval threshold, it is merged with the previous timestamp. (2) Due to inconsistencies in the data transmission frequencies of different sensors, data alignment is required. A fixed sampling time step is set, denoted as . In this embodiment, 1 second is taken. Based on this, the collected real-time navigation status data is mapped onto a unified timeline, ensuring that each timestamp has corresponding information on bow direction, ground speed, actual rudder angle, and latitude and longitude, and that the difference between two adjacent timestamps is always equal to... ; (3) The aligned real-time navigation status data is smoothed by a moving average filtering algorithm to filter out noise caused by interference factors such as wave impact, and a time-series data stream is obtained.

[0029] It should be noted that since the intensity of a ship's maneuvering depends primarily on changes in its motion state and is unrelated to its latitude and longitude, maneuverability parameters are directly involved in the calculation of the subsequent navigation maneuverability index, while positioning parameters are not involved in the calculation of the navigation maneuverability index. They are only compressed as part of the ship's real-time navigation status data during compression processing to ensure the integrity of the ship's geographical location information.

[0030] In this way, by preprocessing the real-time navigation status data, outliers and noise interference in the data are eliminated, resulting in a time-series data stream with uniform time intervals and smooth values, providing accurate and reliable data for subsequent calculations.

[0031] S2: By utilizing time-series data streams and comprehensively considering changes in the ship's heading, speed, and rudder angle, a navigation maneuverability index is obtained that reflects the current intensity of the ship's maneuvers.

[0032] Specifically, based on the characteristics of ship dynamics, and taking into account changes in the ship's heading, speed, and rudder angle deviation, a weighting coefficient is obtained through statistical analysis experiments to weight and fuse these three physical quantities, resulting in a navigation maneuverability index that reflects the intensity of the ship's current maneuvers.

[0033] Navigational maneuverability index The relationship is as follows:

[0034] in, The navigation maneuverability index is given at time t. The larger the value, the more violent the ship's movements. This is the sampling time step; Indicates the change in the ship's heading. Indicates changes in a ship's speed. This indicates that the ship's rudder angle has deviated. , , These are the weighting coefficients for changes in heading, speed, and rudder angle deviation, respectively. Let be the shortest angular distance from the bow at time t; and These are the ground speeds at times t and t-1, respectively. The actual rudder angle at time t. As the reference rudder angle, this embodiment takes the longitudinal midsection direction of the ship as the reference rudder angle, that is... .

[0035] It should be noted that, in order to address the issue of abrupt changes in the ship's navigation direction between 0° and 360°, the shortest angular distance in the bow direction is introduced. The relationship is as follows:

[0036] in, and These are the ship's headings at times t and t-1, respectively, with values ​​ranging from 0° to 360°.

[0037] It should be noted that the weighting coefficients , , It is based on historical navigation data of ships and obtained through statistical analysis experiments. The specific steps are as follows: 1. In this embodiment, a 76,000-ton Panamax bulk carrier was selected as the experimental object. This ship has typical merchant ship motion characteristics of large inertia and slow response. 2. To obtain a sample encompassing the ship's extreme maneuver characteristics, the following three standard ship maneuvering tests were performed on the test subject under standard sea states, each lasting 3600 seconds: (1) Z-shaped maneuvering experiment, specifically 10° / 10° and 20° / 20° maneuvering, aimed to stimulate the dynamic response of the ship to frequently change its heading, and to calibrate the weighting coefficient of the heading change; (2) Emergency reversing test: The command to reverse at full speed is issued directly while the ship is moving forward at full speed. The purpose is to induce a sudden change in the ship's speed and to calibrate the weighting coefficient of the speed change. (3) Full speed turn test: According to the ship maneuverability standards of the International Maritime Organization, a full left turn operation was performed. Since 35° is defined as the full rudder angle of the mechanical limit of the merchant ship's steering gear in the international construction standards for merchant ships, this embodiment also selects a full left turn of 35° to stimulate the ship's turning motion at the limit rudder angle and to calibrate the weighting coefficient of the rudder angle deviation. It should be noted that the same applies to the full right turn operation. In this embodiment, the full left turn data is selected as the experimental data.

[0038] 3. During the ship maneuverability tests conducted according to the above three standards, timestamps and the bow direction corresponding to each timestamp are synchronously collected through the shipboard data interface unit. Ground speed Actual rudder angle The reference rudder angle is defined as the longitudinal midsection direction of the ship, i.e., 0°; left rudder is defined as positive and right rudder as negative; the following three data sequences are obtained: (1) Sequence of bow changes ; (2) Speed ​​change sequence ; (3) Rudder angle deviation sequence .

[0039] 4. Determine the statistical boundary: Due to phenomena such as GPS signal drift and poor contact of the rudder angle feedback potentiometer, the collected data may generate instantaneous electromagnetic interference pulses. Therefore, this embodiment does not directly select the maximum value of the data sequence, but uses the 95th percentile value as the statistical upper limit of each collected data under severe ship maneuvering, so as to avoid the influence of occasional noise on the experimental results.

[0040] It should be noted that the 95th percentile value is specifically determined by: sorting the data in the three data sequences above in reverse order, finding the data at the 95th percentile position. The experiment lasted 3600 seconds, with a sampling time step of 1 second. Therefore, the 3420th data point is the 95th percentile; [find...] , , The 3420th data point after reverse sorting is denoted as follows: , , .

[0041] 5. To ensure that the bow direction, ground speed, and actual rudder angle contribute equally to the navigation maneuverability index when they reach their respective statistical upper limits, the initial weights are calculated using the derivative normalization method, as follows: (1) Initial weights for changes in bow direction: ; (2) Initial weights for speed changes: ; (3) Rudder angle deviates from initial weight: .

[0042] In this embodiment, we obtain , , Correspondingly, , , ;because If the values ​​are too small, it will be inconvenient to configure engineering parameters, so the magnitude needs to be adjusted. In this embodiment, the weight of the rudder angle deviation is increased by 40 times. In order to keep the ratio unchanged, the other two weights are also increased by 40 times. The final weight coefficients are... , , .

[0043] It can be seen that the weighting coefficients obtained through statistical analysis experiments based on historical navigation data of ships scientifically solve the problem of inconsistent dimensions of multi-source data; by assigning high weights to ground speed, which has small numerical changes but large impact on ships, and low weights to actual rudder angle, which has large numerical changes but small impact on ships, the deviation of calculation results caused by differences in numerical magnitude is avoided, thus ensuring the objectivity of the obtained navigation maneuverability index.

[0044] Figure 2 This is a comparative analysis chart of ship navigation status and navigation maneuverability index provided by an embodiment of the present invention. The upper chart is a graph showing the change of maneuverability parameters of real-time ship navigation status data over time, and the lower chart is a graph showing the change of navigation maneuverability index over time. It can be seen that in the first 0-200 seconds, the ship is sailing smoothly and the value of navigation maneuverability index is close to 0; in the 200-300 seconds, the ship maneuvers violently and the value of navigation maneuverability index increases rapidly.

[0045] Thus, the navigation maneuverability index obtained in this step can comprehensively assess the ship's motion status in real time and objectively by taking into account the ship's heading, ground speed, and actual rudder angle. During stable navigation, the navigation maneuverability index remains at a low level, while it will rapidly increase during situations of violent maneuvering such as turning, changing speed, or emergency collisions. It is the core foundation for achieving intelligent adjustment.

[0046] S3: Based on the navigation maneuverability index, the length of the sliding window of the compression algorithm is determined using a preset inverse attenuation model, wherein the length of the sliding window is negatively correlated with the navigation maneuverability index.

[0047] Specifically, the length of the sliding window in the compression algorithm is dynamically adjusted using the navigation maneuverability index. The adjustment strategy follows the inverse control principle, that is, the smaller the navigation maneuverability index, the larger the sliding window; the larger the navigation maneuverability index, the smaller the sliding window.

[0048] Length of the sliding window at time t The relationship is as follows:

[0049] in, It is a rounding function; This is the preset minimum length of the sliding window. This is the preset maximum length of the sliding window. This is the attenuation sensitivity coefficient. It is a natural constant.

[0050] When a ship is maneuvering violently, the navigation maneuverability index increases. To prevent the CPU from overloading due to invalid searches in excessively large historical data, the length of the sliding window is shortened. When the ship is sailing smoothly, the navigation maneuverability index decreases, and the length of the sliding window is extended to ensure maximum coverage of long-term historical repetitive data.

[0051] It should be noted that, since embedded systems are typically used on ships, this embodiment... and The setting standards are as follows: (1) The minimum length of the sliding window is set to 4096 bytes, which is usually the size of a memory page in the operating system. This not only matches the minimum sector write unit of the onboard storage medium, but also ensures millisecond-level search time, thus avoiding the loss of critical data while maintaining the most basic compression efficiency. (2) Taking 32768 bytes, this is the maximum length of the sliding window for the general LZ77 algorithm and its variants. For text or structured data, such as NMEA statements, this size is sufficient to cover most repetitive patterns. Increasing it further will have limited effect on improving compression efficiency, but memory consumption will double. Attenuation sensitivity coefficient This is used to control the sensitivity of the sliding window length to the ship's maneuverability; to avoid An excessively large value can cause the sliding window to erroneously contract when the ship is sailing smoothly. A value that is too small causes the sliding window to contract too slowly during periods of intense ship maneuvering. This invention addresses this issue by obtaining the value through response calibration experiments based on the ship's standard steering conditions. The specific steps are as follows: 1. Define standard operating conditions. According to the International Maritime Organization's ship maneuverability standards, the standard positions for Z-shaped maneuvering tests are 10° and 20°. Therefore, this embodiment selects the median of these two positions, 15°, which is the actual rudder angle. As a standard turning condition, it represents the engineering critical value between stable navigation and violent maneuvering of a ship. When it is considered a smooth voyage, This was considered a period of intense maneuvering; 2. Obtain the baseline navigation maneuverability index. A 76,000-ton Panamax bulk carrier was selected as the test object. Under standard sea states, the ship maintained... Maneuverability parameters for stable turning and real-time navigation status data of the vessel: (1) The ship's speed changes very little, therefore ; (2) The rudder angle deviation is a constant value. The reference rudder angle is defined as the longitudinal midsection direction of the ship, i.e., 0°. Therefore ; (3) The ship's heading change is at a stable angle. Actual measurements show that the actual rudder angle for a 76,000-ton Panamax bulk carrier is... The average turning rate is ,therefore ; Substituting the maneuverability parameters from the aforementioned real-time navigation status data of the vessel into the formula for the navigation maneuverability index, we obtain the navigation maneuverability index of the vessel under standard turning conditions, denoted as . , .

[0052] 3. Calibrate the attenuation sensitivity coefficient Based on the sensitivity design principles of the control system, the exponential decay model has the optimal tangent slope at 50%, therefore the length of the sliding window under standard steering conditions is... This achieves a balance between retaining half of the search capability to maintain compression efficiency under standard steering conditions and releasing half of the computing resources to handle potential unforeseen circumstances; and Substituting these into the formula for the length of the sliding window, we get... This is the attenuation sensitivity coefficient that has been experimentally calibrated in this embodiment.

[0053] Figure 3 This is a graph showing the change of the sliding window provided in an embodiment of the present invention. It can be seen that the curve is U-shaped, and the length of the sliding window is continuously and adaptively adjusted. Figure 2 The graph showing the change of the navigation maneuverability index over time reveals that the length of the sliding window is negatively correlated with the navigation maneuverability index.

[0054] In this way, by using the exponential decay model to establish a nonlinear mapping between the navigation state and the algorithm parameters, the intelligent dynamic adjustment of the sliding window length is realized. The length of the sliding window is increased during stable navigation to maximize the compression ratio, and the length of the sliding window is reduced during violent ship maneuvers to ensure real-time performance, effectively solving the problem of uneven resource utilization.

[0055] S4: Configure the length of the sliding window to the search range of the compression encoder, compress and encrypt the real-time navigation status data of the ship, obtain the evidence data packet and write it to the ship's onboard storage medium.

[0056] Specifically, the length of the sliding window The control commands are converted into compressed data, and the navigation data of the ship is finally solidified through cryptographic transformation and storage strategies that conform to international standards.

[0057] 1. Compression processing (1) In this embodiment, the LZ77 encoder is selected as the compression encoder, following the RFC 1951 standard. The parameters are input in real time as the lookup range of the LZ77 encoder; (2) The LZ77 encoder maintains a history buffer with a fixed physical size. However, the logical search pointer only works when the length is [length missing]. Search within the historical buffer; (3) Within the set search range, the LZ77 encoder encodes the real-time navigation status data to generate a binary data stream; Based on the principle of data locality, when a ship is maneuvering violently, its navigation maneuverability index increases. Limiting the search range can effectively reduce the CPU cache miss rate without significantly reducing compression efficiency.

[0058] It should be noted that this embodiment adopts a strategy of separating calculation and evidence storage. During the encapsulation process, although the positioning parameters are not used as independent variables in the calculation of the length of the sliding window, they are also compressed as part of the real-time navigation status data of the ship, since they are the core evidence storage elements of the ship's navigation trajectory. This can not only respond accurately when the ship's status changes, but also ensure the traceability of the ship's geographical coordinates in maritime accidents.

[0059] 2. Encryption processing (1) Following the NIST FIPS 197 standard, this embodiment uses the AES-256 algorithm in the cryptographic block chaining mode, and uses a pre-set ship's unique key to encrypt the binary data stream and generate ciphertext data blocks; (2) In accordance with the NIST FIPS 180-4 standard, this embodiment uses the SHA-256 algorithm to calculate the encrypted data block and generate a 256-bit digital digest. Any bit-level tampering with the real-time navigation status data of the ship will cause the digest verification to fail. (3) Encapsulate the ciphertext data block together with the digital digest to obtain the evidence storage data packet.

[0060] 3. Data storage The evidence storage data packet is physically written through the following two independent channels: (1) The evidence data packet is written directly to the shipboard storage medium via the SATA interface, in accordance with the IEC 61996 standard. The shipboard storage medium is encapsulated in a protective bag that conforms to the VDR standard. In this embodiment, the direct I / O mode is selected to bypass the operating system cache and ensure that the data is written to the disk in the event of an emergency. (2) Push the evidence data packet into the satellite communication buffer queue and dynamically adjust the transmission frequency according to the current compression efficiency. When the ship is sailing smoothly, the evidence data packet is small and is uploaded in batches; when the ship is maneuvering violently, the evidence data packet is larger and key frames are uploaded first to ensure remote shore backup of key data under limited bandwidth.

[0061] Figure 4 The data storage comparison diagram provided by the embodiments of the present invention shows that the present invention is close to the prior art B in terms of average compression ratio and far exceeds the prior art A; and is close to the prior art A in terms of peak calculation time and far lower than the prior art B, demonstrating that the present invention successfully balances compression efficiency and real-time performance.

[0062] In this way, by configuring the length of the dynamically adjusted sliding window as the search range of the compression encoder and applying it to the actual compression process, combined with encryption technology, not only is real-time writing and storage of data under high-load conditions ensured, but also the confidentiality and integrity of the data are guaranteed, achieving efficient and secure storage of ship navigation data.

Claims

1. A method for securely storing ship navigation data, characterized in that, include: Real-time navigation status data of the vessel is collected. The real-time navigation status data includes the vessel's maneuverability parameters and positioning parameters. The positioning parameters include the vessel's latitude and longitude information. The maneuverability parameters include the vessel's heading, ground speed, and actual rudder angle. The real-time navigation status data is preprocessed to obtain a time-series data stream containing timestamps and the vessel's latitude and longitude information. Using the aforementioned time-series data stream, and by comprehensively considering changes in the ship's heading, speed, and rudder angle deviation, a navigation maneuverability index reflecting the current intensity of the ship's maneuvers is obtained. Based on this navigation maneuverability index, the length of the sliding window for the LZ77 compression algorithm is determined using a preset reverse attenuation model. The length of the sliding window satisfies the following relationship: in, Let be the length of the sliding window at time t. For the floor function, This is the preset minimum length of the sliding window. This is the preset maximum length of the sliding window. This is the attenuation sensitivity coefficient. It is a natural constant. The navigation maneuverability index at time t; The length of the sliding window is input into the compression encoder as a configuration parameter to compress the real-time navigation status data to obtain a binary data stream. The binary data stream is then encrypted and its integrity is verified to obtain a certificate data packet, which is then written to the shipboard storage medium.

2. The method for securely storing ship navigation data according to claim 1, characterized in that, The navigation maneuverability index satisfies the following relationship: in, Let be the navigation maneuverability index at time t. Indicates the change in the ship's heading. Indicates changes in a ship's speed. This indicates that the ship's rudder angle has deviated. , , These are the weighting coefficients for the changes in bow direction, speed, and rudder angle deviation, respectively. Let be the shortest angular distance from the bow at time t. For the sampling time step, and These are the ground speeds at times t and t-1, respectively. The actual rudder angle at time t. This is the reference rudder angle.

3. The method for securely storing ship navigation data according to claim 2, characterized in that, The shortest angular distance from the bow satisfies the following relationship: in, and These are the ship's headings at times t and t-1, respectively, with values ​​ranging from 0 degrees to 360 degrees.

4. The method for securely storing ship navigation data according to claim 1, characterized in that, The preprocessing includes aligning and denoising the real-time navigation status data.

5. The method for securely storing ship navigation data according to claim 1, characterized in that, The compression process includes: configuring the length of the sliding window as the search range of the compression encoder, the compression encoder including a history buffer; when encoding the real-time navigation status data, by limiting the offset of the logical search pointer of the history buffer, searching only within the search range for strings that match the real-time navigation status data and encoding them to generate the binary data stream.

6. The method for securely storing ship navigation data according to claim 2, characterized in that, The weighting coefficients for changes in heading, speed, and rudder angle deviation are obtained through statistical analysis experiments based on the ship's historical navigation data.

7. The method for securely storing ship navigation data according to claim 1, characterized in that, The encryption process and integrity verification include: performing cryptographic transformation on the binary data stream to obtain ciphertext data blocks; calculating digital digests based on the ciphertext data blocks; and encapsulating the ciphertext data blocks and the digital digests to obtain the evidence storage data packet.

8. The method for securely storing ship navigation data according to claim 1, characterized in that, The attenuation sensitivity coefficient is obtained through response calibration experiments based on the ship's standard steering conditions.

9. A ship navigation data secure storage system, characterized in that, include: A processor and a memory, the memory storing computer program instructions that, when executed by the processor, implement the method for securely storing ship navigation data according to any one of claims 1-8.

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