Ship navigation data security storage method and system

Abstract

The present application relates to the field of digital information transmission, in particular to a ship navigation data security evidence method and system. The method comprises: collecting and preprocessing real-time navigation state data of the ship; calculating a navigation maneuverability index reflecting the current maneuvering intensity of the ship by using the preprocessed real-time navigation state data of the ship; determining the length of the sliding window of the compression algorithm based on the navigation maneuverability index through a preset reverse attenuation model, wherein the length of the sliding window is negatively correlated with the navigation maneuverability index; configuring the length of the sliding window as the lookup range of the compression encoder, and performing compression and encryption processing on the real-time navigation state data of the ship to obtain an evidence data packet and write it into a shipborne storage medium. The present application dynamically adjusts the compression strategy, effectively balances the storage space utilization rate and the consumption of computing resources while ensuring real-time data evidence, and improves the transmission and storage efficiency of ship navigation data.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of digital information transmission, in particular to a ship navigation data security storage method and system. BACKGROUND

[0002] In the modern intelligent navigation system, the ship navigation data recorder plays a key role similar to the black box of an airplane, which is responsible for recording real-time multi-source heterogeneous data such as the position, speed, heading, rudder angle, etc. of the ship. These data are not only the core basis for maritime accident investigation, but also the important basis for navigation efficiency analysis and remote monitoring. Since the ocean-going ships mainly rely on maritime satellite link for communication with the shore during navigation, the bandwidth of satellite communication is extremely limited and the cost is high. Therefore, efficient data compression is a necessary means to reduce operating costs.

[0003] At present, the industry generally uses the LZ77 algorithm to compress ship data losslessly. This algorithm uses a sliding window mechanism to find repeated strings in historical data to achieve compression. However, the existing application scheme usually uses a fixed-length sliding window, which cannot adapt to the complex and variable navigation conditions of the ship. During the smooth period of long straight sailing and speed maintenance of the ship, the fixed and small sliding window cannot cover the long-period repeated data, resulting in that the compression potential is not fully tapped and the bandwidth is wasted.

[0004] On the contrary, during the complex maneuvering period of the ship entering and leaving the port or emergency collision avoidance, the data changes dramatically and the historical correlation decays rapidly. At this time, if a larger fixed window is maintained, the algorithm will perform invalid search in a large number of irrelevant historical data, which not only cannot improve the compression rate, but also will occupy a large amount of computing resources, causing data writing delay. In the extreme accident conditions such as power failure or collision, this delay may cause the data to be lost permanently due to the delay in storage. SUMMARY

[0005] In order to solve the problem that the fixed sliding window in the existing ship data storage technology cannot balance the high compression rate in the smooth period and the real-time performance in the maneuvering period, resulting in waste of storage resources and data loss, the present application provides a ship navigation data security storage method and system.

[0006] In the first aspect, the present application provides a ship navigation data security storage method, which adopts the following technical scheme:

[0007] Collect real-time sailing state data of a ship, the real-time sailing state data comprising maneuverability parameters and positioning parameters of the ship, the positioning parameters comprising latitude and longitude information of the ship, and the maneuverability parameters comprising a ship heading, a ground speed, and an actual rudder angle of the ship;Preprocess the real-time sailing state data to obtain a time series data stream comprising a time stamp and the latitude and longitude information of the ship;Obtain a sailing maneuverability index reflecting a current maneuvering intensity of the ship by comprehensively considering changes in the ship heading, the ground speed, and the rudder angle deviation of the ship by using the time series data stream;Determine a length of a sliding window of an LZ77 compression algorithm based on the sailing maneuverability index by using a preset reverse attenuation model, the length of the sliding window satisfying a relationship:

[0008]

[0009] wherein, is the length of the sliding window at time t, is a rounding function, is a preset minimum length of the sliding window, is a preset maximum length of the sliding window, is an attenuation sensitivity coefficient, is a natural constant, is the sailing maneuverability index at time t;

[0010] Input the length of the sliding window as a configuration parameter into a compression encoder, perform compression processing on the real-time sailing state data to obtain a binary data stream, perform encryption processing and integrity checking on the binary data stream, obtain a notarization data packet, and write the notarization data packet into a shipborne storage medium.

[0011] The present application can evaluate the motion state of the ship in real time by collecting real-time sailing state data of the ship and calculating a sailing maneuverability index, and provide accurate quantitative basis for subsequent operations;Meanwhile, by adaptively determining the length of the sliding window, the length of the sliding window can be expanded to improve the compression efficiency when the ship sails smoothly, and the length of the sliding window can be reduced to reduce the calculation load when the maneuvering is intense, so that the optimal balance between compression efficiency and real-time performance is realized under the premise of ensuring data security.

[0012] Further, the sailing maneuverability index satisfies a relationship:

[0013]

[0014] wherein, is the sailing maneuverability index at time t, represents a change in the ship heading, represents a change in the ground speed of the ship, represents a rudder angle deviation of the ship, , , are weight coefficients of the heading change, the speed change and the rudder angle deviation respectively, is the shortest angular distance of the heading at time t, is the sampling time step, and are the ground speeds at time t and time t-1 respectively, is the actual rudder angle at time t, is the reference rudder angle.

[0015] The application eliminates logical ambiguity caused by data mutation by unifying the dimensions of various physical quantities into square terms and introducing the shortest angular distance of the heading, and ensures the objectivity and physical authenticity of the evaluation index.

[0016] Further, the shortest angular distance of the heading satisfies the relationship:

[0017]

[0018] wherein, and are the headings at time t and time t-1 respectively, and the value range is 0 degree to 360 degrees.

[0019] Further, the preprocessing comprises: aligning and denoising the real-time navigation state data.

[0020] Further, the compression processing comprises: configuring the length of the sliding window as the lookup range of the compression encoder; when encoding the real-time navigation state data, by limiting the offset of the logical search pointer of the history buffer of the compression encoder, only searching for a string matching the real-time navigation state data within the lookup range and encoding to generate the binary data stream.

[0021] By mapping the length of the sliding window to the lookup range of the compression encoder, when the ship maneuver is intense and causes rapid decay of data correlation, the lookup range can be forcibly reduced, the matching operation of invalid strings is effectively reduced, calculation congestion is prevented, and the response capability of millisecond level is still ensured on the low-power shipborne hardware.

[0022] Further, the weight coefficients of the heading change, the speed change and the rudder angle deviation are obtained through statistical analysis experiments based on the historical navigation data of the ship.

[0023] Further, the encryption processing and integrity checking comprise: performing a cryptography transformation on the binary data stream to obtain a ciphertext data block; calculating a digital digest based on the ciphertext data block; and encapsulating the ciphertext data block and the digital digest to obtain the evidence storage data packet.

[0024] The application adopts the strategy of combining ciphertext data blocks and digital digest to guarantee the confidentiality and integrity of real-time navigation state data; wherein, the commercial sensitive information such as ship position and route is effectively protected through cryptographic transformation; and the tampering or loss of data in the storage or transmission process can be rapidly screened through the calculation of digital digest.

[0025] Further, the attenuation sensitivity coefficient is obtained through a response calibration experiment based on a standard turning condition of the ship.

[0026] In a second aspect, the application provides a ship navigation data security storage system, which adopts the following technical scheme:

[0027] The ship navigation data security storage system comprises a processor and a memory, and the memory stores computer program instructions, which realize the above-mentioned ship navigation data security storage method when executed by the processor.

[0028] By adopting the above technical scheme, the above-mentioned ship navigation data security storage method is generated into a computer program and stored in the memory to be loaded and executed by the processor, so that a terminal device is made according to the memory and the processor, and the use is facilitated.

[0029] The application has the following technical effects:

[0030] The ship navigation data security storage system provided by the application breaks the limitation of traditional fixed window compression by introducing a navigation maneuverability index, expands the length of the sliding window during the smooth navigation period which occupies most of the time, such as straight sailing and anchoring, to ensure the compression efficiency, not only greatly saves the satellite communication cost, but also effectively prolongs the data retention period of the shipborne storage medium.

[0031] During the period of high incidence of accidents such as collision, grounding and emergency avoidance, the data flow bursts instantaneously and the correlation is extremely low, the application rapidly shrinks the sliding window within milliseconds through the preset reverse attenuation model, avoids searching a large amount of invalid historical data, ensures that all key navigation data can be written in time at the last critical moment before the ship power failure or damage, and reserves the data for accident investigation.

[0032] Unlike simple log recording, the application deeply integrates dynamic compression and cryptography technology, constructs a complete evidence chain through the synchronous packaging of ciphertext data blocks and digital digest, and meets the requirements of modern intelligent shipping for data integrity and legal compliance. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1is a flowchart of a ship navigation data security evidence method provided by an embodiment of the present application;

[0034] Figure 2 is a comparative analysis diagram of a ship navigation state and a navigation maneuverability index provided by an embodiment of the present application;

[0035] Figure 3 is a sliding window change diagram provided by an embodiment of the present application;

[0036] Figure 4 is a data security evidence comparative diagram provided by an embodiment of the present application. DETAILED DESCRIPTION

[0037] An embodiment of the present application provides a ship navigation data security evidence method, referring to Figure 1 , comprising steps S1-S4:

[0038] S1: collecting real-time navigation state data of a ship and performing preprocessing to obtain a time series data stream containing a time stamp and latitude and longitude information of the ship.

[0039] 1. Multi-source data collection and definition

[0040] According to the IEC 61162 standard protocol, real-time navigation state data of the ship is collected through a shipboard data interface unit, including a time stamp, maneuverability parameters, and positioning parameters, wherein the positioning parameters are latitude and longitude positions of the ship, and the maneuverability parameters include a ship heading , a ground speed , and an actual rudder angle ; is a navigation direction of the ship at time , ranging from 0° to 360°, is a ground speed of the ship at time , is a deflection angle of a rudder vane at time , negative for port rudder and positive for starboard rudder.

[0041] 2. Preprocessing

[0042] (1) Set a minimum time interval threshold, which is 0.01 seconds in this embodiment, and if the difference between the current time stamp and the previous time stamp is less than the minimum time interval threshold, merge with the previous time stamp.

[0043] (2) Since the data sending frequencies of different sensors are inconsistent, the data needs to be aligned, and a fixed sampling time step is set, denoted as , which is 1 second in this embodiment, and For the benchmark, the collected real-time navigation state data is mapped to a unified timeline, ensuring that each timestamp has corresponding ship heading, ground speed, actual rudder angle, latitude and longitude information, and the difference between adjacent two timestamps is equal to ;

[0044] (3) The aligned real-time navigation state data is smoothed by using a moving average filtering algorithm to filter out noise caused by sea wave impact and other interference factors, obtaining a time series data stream.

[0045] It should be noted that since the degree of ship maneuvering depends mainly on the change of motion state, and has nothing to do with the latitude and longitude position of the ship, therefore, the maneuvering parameter directly participates in the calculation of the subsequent navigation maneuverability index, and the positioning parameter does not participate in the calculation of the navigation maneuverability index, it is only compressed as part of the real-time navigation state data of the ship during compression, to ensure the integrity of the geographical position information of the ship.

[0046] In this way, by preprocessing the real-time navigation state data, the abnormal points and noise interference in the data are eliminated, obtaining a time series data stream with uniform time interval and smooth numerical value, providing accurate and reliable data for subsequent calculation.

[0047] S2: Using the time series data stream, by comprehensively considering the ship's heading change, speed change, and rudder angle deviation, the navigation maneuverability index reflecting the current maneuvering intensity of the ship is obtained.

[0048] Specifically, based on the ship dynamics characteristics, the ship's heading change, speed change, and rudder angle deviation are comprehensively considered, and the weight coefficients are obtained by statistical analysis experiments to weight and fuse the three physical quantities, obtaining the navigation maneuverability index reflecting the current maneuvering intensity of the ship.

[0049] Navigation maneuverability index The relationship is as follows:

[0050]

[0051] Where, is the navigation maneuverability index at time t, the larger the value, the more intense the ship's action; is the sampling time step; represents the change of the ship's heading, represents the change of the ship's speed, represents the deviation of the ship's rudder angle, , , are the weight coefficients of the heading change, speed change, and rudder angle deviation, respectively; is the shortest angular distance of the ship's heading at time t; and the ground speed at time t and time t-1, respectively; is the actual rudder angle at time t, is the reference rudder angle, and the longitudinal centerplane direction of the ship is taken as the reference rudder angle in the embodiment, .

[0052] It should be noted that, in order to solve the problem of sudden change of the ship's sailing direction in 0°-360°, the shortest angular distance of the ship's heading is introduced , and the relationship is:

[0053]

[0054] , wherein, and are the ship's heading at time t and time t-1, respectively, and the value range is 0°-360°.

[0055] It should be noted that the weight coefficients , , are obtained through statistical analysis experiments based on the historical navigation data of the ship, and the specific steps are as follows:

[0056] 1. In the embodiment, a 76,000-ton Panama bulk carrier is selected as the experimental object, which has the typical ship motion characteristics of large inertia and slow response.

[0057] 2. In order to obtain samples covering the extreme motion characteristics of the ship, the following three standard ship maneuverability experiments are performed on the experimental object under standard sea conditions, each experiment lasting 3600 seconds:

[0058] (1) Z-shaped maneuvering experiment, specifically performing 10° / 10° and 20° / 20° maneuvering, aiming to stimulate the dynamic response of the ship frequently changing the ship's heading, and used to calibrate the weight coefficient of the change of the ship's heading;

[0059] (2) Emergency astern experiment, directly issuing a full-speed astern command in full-speed ahead state, aiming to stimulate the sharp change of the ship's speed, and used to calibrate the weight coefficient of the change of the ship's speed;

[0060] (3) Full-speed turning experiment, according to the ship maneuverability standard of the International Maritime Organization, left full rudder turning operation is performed, since 35° is defined as the full rudder angle of the mechanical limit of the ship's rudder in the international construction standard of merchant ships, therefore, the embodiment also selects left full rudder 35°, aiming to stimulate the turning motion of the ship under the limit rudder angle, and used to calibrate the weight coefficient of the deviation of the rudder angle; It should be noted that the right full rudder turning operation is the same, and the left full rudder turning data is selected as the experimental data in the embodiment.

[0061] 3、In the process of performing the above three standard ship maneuverability experiments, the time stamp, the ship heading corresponding to each time stamp , the ground speed , the actual rudder angle are synchronously collected through the shipboard data interface unit; the reference rudder angle is defined as the longitudinal section direction of the ship, i.e. 0°, and the left rudder is defined as a positive value and the right rudder is defined as a negative value; the following three data sequences are obtained:

[0062] (1) Ship heading change sequence ;

[0063] (2) Speed change sequence ;

[0064] (3) Rudder angle deviation sequence .

[0065] 4、Determine the statistical boundary: due to phenomena such as GPS signal drift, poor contact of the rudder angle feedback potentiometer, etc., the collected data may produce instantaneous electromagnetic interference pulses, therefore, this embodiment does not directly select the maximum value of the data sequence, but uses the 95% quantile value as the statistical upper limit of each data collected under the ship maneuvering, to avoid the influence of occasional noise on the experimental results.

[0066] It should be noted that the 95% quantile value is as follows: for the data in the above three data sequences, the data is sorted in descending order, the data at the 95% position is found, the experimental duration is 3600 seconds, the sampling time step is 1 second, Therefore, the 3420th data is the 95% quantile value; the , , 3420th data in the descending order is found, respectively denoted as , , .

[0067] 5、In order to ensure that the ship heading, the ground speed and the actual rudder angle have the same contribution to the navigation maneuverability index when reaching their respective statistical upper limits, the derivative normalization method is used to calculate the initial weight, as follows:

[0068] (1) Ship heading change initial weight: ;

[0069] (2) Speed change initial weight: ;

[0070] (3) Rudder angle deviation initial weight: .

[0071] In this embodiment, the , 、 Correspondingly, 、 、 Because The value is too small to be convenient for engineering parameter configuration, and thus magnitude adjustment is required, the weight of the rudder angle deviation is enlarged by 40 times in the embodiment, in order to keep the proportion unchanged, the other two weights are also enlarged by 40 times, and the final weight coefficient 、 、 .

[0072] It can be seen that the weight coefficient obtained through statistical analysis experiment based on the historical navigation data of the ship scientifically solves the problem of non-uniform dimension of multi-source data; by assigning a high weight to the ground speed which has small numerical value but great influence on the ship and assigning a low weight to the actual rudder angle which has large numerical value but small influence on the ship, deviation of the calculation result caused by magnitude difference of the numerical value is avoided, and the objectivity of the obtained navigation maneuverability index is ensured.

[0073] Figure 2 is a comparative analysis diagram of the ship navigation state and the navigation maneuverability index provided by the embodiment of the application, the upper diagram is a diagram of the change of the maneuverability parameter of the real-time navigation state data of the ship with time, and the lower diagram is a diagram of the change of the navigation maneuverability index with time; it can be seen that in the first 0-200 seconds, the ship sails steadily, and the value of the navigation maneuverability index is close to 0; in the 200-300 seconds, the ship maneuvers violently, and the value of the navigation maneuverability index increases rapidly.

[0074] In this way, the navigation maneuverability index obtained in the step can evaluate the motion state of the ship in real time and objectively by comprehensively considering the ship's heading, ground speed and actual rudder angle; in the case of steady sailing, the navigation maneuverability index maintains at a low level, while in the case of violent maneuvering such as turning, speed changing or emergency collision, the navigation maneuverability index increases rapidly, which is the core basis of realizing intelligent adjustment.

[0075] S3: based on the navigation maneuverability index, the length of the sliding window of the compression algorithm is determined by using a preset reverse attenuation model, wherein the length of the sliding window is negatively correlated with the navigation maneuverability index.

[0076] Specifically, the length of the sliding window of the compression algorithm is dynamically adjusted by using the navigation maneuverability index; the adjustment strategy follows the reverse 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.

[0077] The relationship formula of the length of the sliding window at time t is as follows:

[0078]

[0079] 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.

[0080] 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.

[0081] It should be noted that, since embedded systems are typically used on ships, this embodiment... and The setting standards are as follows:

[0082] (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.

[0083] (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.

[0084] 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:

[0085] 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, The time is regarded as a motor;

[0086] 2, the reference navigation maneuverability index is obtained, a 76000-ton Panama bulk carrier is selected as an experimental object, under standard sea conditions, the ship keeps Stable steering is carried out, and the maneuverability parameters of the real-time navigation state data of the ship are collected:

[0087] (1) The ship speed changes very little, so ;

[0088] (2) The rudder angle deviation is a constant value, the reference rudder angle is defined as the longitudinal center plane direction of the ship, that is, 0°, so ;

[0089] (3) The ship's heading changes at a stable angle, and the actual rudder angle of the 76000-ton Panama bulk carrier is The average steering rate is , so ;

[0090] The maneuverability parameters of the real-time navigation state data of the ship are substituted into the relationship formula of the navigation maneuverability index, and the navigation maneuverability index of the ship under the standard steering condition is obtained, denoted as , .

[0091] 3, the decay sensitivity coefficient is calibrated, based on the sensitivity design principle of the control system, the exponential decay model has the best tangent slope at 50%, so the length of the sliding window under the standard steering condition is , which realizes that half of the search capability is retained to maintain the compression efficiency, and half of the calculation resource reserve is released to cope with possible emergencies; together with , the length of the sliding window is substituted into the relationship formula, and , that is, the decay sensitivity coefficient calibrated by the experiment in this embodiment.

[0092] Figure 3 The sliding window change graph provided by the embodiment of the present application can be seen, and the curve is U-shaped, the length of the sliding window is continuously self-adaptively adjusted, and in combination with the navigation maneuverability index change image with time in Figure 2 , it can be seen that the length of the sliding window is negatively correlated with the navigation maneuverability index.

[0093] Thus, the nonlinear mapping between the sailing state and the algorithm parameter is established by using the exponential decay model, and the length of the sliding window is intelligently and dynamically adjusted. When the ship sails steadily, the length of the sliding window is expanded to maximize the compression ratio, and when the ship maneuvers violently, the length of the sliding window is reduced to ensure real-time performance, effectively solving the problem of uneven resource utilization.

[0094] S4: The length of the sliding window is configured as the search range of the compression encoder, and the real-time sailing state data of the ship is compressed and encrypted to obtain the evidence data packet and write it into the on-board storage medium.

[0095] Specifically, the length of the sliding window is converted into a control instruction for compression processing, and the final solidification of the sailing data of the ship is completed through the password conversion and storage strategy conforming to the international standard.

[0096] 1. Compression processing

[0097] (1) In this embodiment, the LZ77 encoder is selected as the compression encoder, which follows the RFC 1951 standard, and the is input in real time as a parameter of the search range of the LZ77 encoder;

[0098] (2) The LZ77 encoder maintains a history buffer, the physical size of which is fixed at , but the logical search pointer only searches within the history buffer with a length of ;

[0099] (3) Within the set search range, the LZ77 encoder encodes the real-time sailing state data to generate a binary data stream;

[0100] Based on the principle of data locality, when the ship maneuvers violently, the sailing maneuverability index of the ship increases, and limiting the search range can effectively reduce the CPU cache miss rate without significantly reducing the compression efficiency.

[0101] It should be noted that this embodiment adopts the strategy of separating calculation and evidence, and in the packaging process, although the positioning parameter is not involved in the calculation of the length of the sliding window as an independent variable, since it is a core evidence element of the ship's sailing trajectory, it is also compressed as part of the real-time sailing state data of the ship. This not only allows for accurate response when the ship's state changes, but also ensures the traceability of the ship's geographic coordinates in maritime accidents.

[0102] 2. Encryption processing

[0103] (1) According to the NIST FIPS 197 standard, the embodiment selects the cipher block chaining mode of the AES-256 algorithm, uses the preset unique key of the ship to encrypt the binary data stream, and generates a ciphertext data block;

[0104] (2) According to the NIST FIPS 180-4 standard, the embodiment selects the SHA-256 algorithm to calculate the ciphertext data block, and generates a 256-bit digital digest. Any bit-level tampering of the real-time sailing state data of the ship will cause the digest verification to fail;

[0105] (3) The ciphertext data block and the digital digest are encapsulated together to obtain a data storage package.

[0106] 3, Data storage

[0107] The data storage package is physically written through the following two independent channels:

[0108] (1) The data storage package is directly written into the on-board storage medium through the SATA interface, which complies with the IEC 61996 standard. The on-board storage medium is encapsulated in a protective capsule that meets the VDR standard. The embodiment selects the direct I / O mode to bypass the operating system cache, ensuring that the data is written to the disk in an instant in the event of an emergency;

[0109] (2) The data storage package is pushed into the satellite communication cache queue, and the sending frequency is dynamically adjusted according to the current compression efficiency. When the ship is sailing smoothly, the data storage package is small, and batch uploading is performed. When the ship is maneuvering violently, the data storage package increases, and the key frame is uploaded preferentially to ensure that the key data is backed up remotely on the shore in a limited bandwidth.

[0110] Figure 4 The data storage comparison chart provided by the embodiment of the present application can be seen. The average compression rate of the present application is close to the prior art B and much higher than the prior art A. The peak calculation time is close to the prior art A and much lower than the prior art B, which reflects that the present application successfully balances the compression efficiency and real-time performance.

[0111] In this way, by configuring the length of the dynamically adjusted sliding window as the lookup range of the compression encoder and applying it to the actual compression process, combined with encryption technology, not only the real-time writing and storage of data under high load conditions are ensured, but also the confidentiality and integrity of the data are guaranteed, and efficient and safe data storage of ship sailing data is achieved.

Claims

1. A method for securely recording ship navigation data, characterized in that, The method comprises: collecting real-time sailing state data of a ship, the real-time sailing state data comprising maneuverability parameters and positioning parameters of the ship, the positioning parameters comprising latitude and longitude information of the ship, and the maneuverability parameters comprising a ship heading, a ground speed, and an actual rudder angle of the ship; preprocessing the real-time sailing state data to obtain a time series data stream comprising time stamps and latitude and longitude information of the ship; ; is a sailing maneuverability index at time , represents a change in the heading of the ship, represents a change in the sailing speed of the ship, represents a rudder angle deviation of the ship, , , are weight coefficients of the heading change, the sailing speed change, and the rudder angle deviation, respectively, is a shortest angle distance of the heading at time , is a sampling time step, and are ground speeds at time and time , respectively, is an actual rudder angle at time , is a reference rudder angle; using the time series data stream, a sailing maneuverability index reflecting a current maneuvering intensity of the ship is obtained by comprehensively considering changes in the ship heading, the ground speed, and the rudder angle, and the sailing maneuverability index satisfies a relationship: ; and are the heading of the ship at time and time , respectively, taking values in the range 0 to 360 degrees; a shortest angular distance of the ship heading satisfies a relationship: ; wherein is a length of the sliding window at time t, is a rounding function, is a minimum length of the preset sliding window, is a maximum length of the preset sliding window, is a decay sensitivity coefficient, is a natural constant; based on the sailing maneuverability index, a length of a sliding window of an LZ77 compression algorithm is determined using a preset reverse attenuation model, and the length of the sliding window satisfies a relationship:

2. The ship navigation data safety archiving method according to claim 1, characterized in that, the length of the sliding window is input into a compression encoder as a configuration parameter, the real-time sailing state data is compressed to obtain a binary data stream, the binary data stream is encrypted and integrity-verified, an evidence data packet is obtained, and the evidence data packet is written into a shipborne storage medium.

3. The method of claim 1, wherein, The preprocessing comprises aligning and denoising the real-time sailing state data.

4. The method of claim 1, wherein, The compression processing comprises configuring the length of the sliding window as a lookup range of the compression encoder, the compression encoder comprising a history buffer area;when encoding the real-time sailing state data, by limiting an offset of a logical search pointer of the history buffer area, only strings matching the real-time sailing state data within the lookup range are searched and encoded to generate the binary data stream.

5. The method of claim 1, wherein, The weight coefficients of the changes in the ship heading, the ground speed, and the rudder angle are obtained based on historical sailing data of the ship through statistical analysis experiments.

6. The method of claim 1, wherein, The encryption processing and the integrity verification comprise performing a cryptography transformation on the binary data stream to obtain a ciphertext data block, calculating a digital digest based on the ciphertext data block, and encapsulating the ciphertext data block and the digital digest to obtain the evidence data packet.

7. A ship navigation data security system, characterized in that, The attenuation sensitivity coefficient is obtained based on a standard turning condition of the ship through a response calibration experiment. The method comprises: a processor and a memory, the memory storing computer program instructions, when the computer program instructions are executed by the processor, a ship sailing data secure evidence method according to any one of claims 1-6 is realized.

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