Satellite constellation communication security transmission method based on post-quantum cryptography

Abstract

This invention discloses a secure transmission method for satellite constellation communication based on post-quantum cryptography, relating to the fields of satellite communication and information security technology. The method includes: analyzing the satellite constellation topology to determine the latency sensitivity level of the secure handshake; pre-screening a set of candidate PQC algorithms based on the sensitivity level; sensing the channel and extracting non-stationary features such as fading depth, duration, and Doppler rate of change; constructing a multi-dimensional joint optimization model with algorithm identifier, fragmentation granularity, redundancy, and modulation and coding scheme as joint decision variables, aiming to maximize the handshake probability within the expected duration; solving the model to generate an adaptive transmission strategy, and performing adaptive non-uniform fragmentation and fountain code encoding on PQC protocol data units; predicting link trends based on Doppler rate of change and dynamically scheduling symbol transmission. This invention achieves deep coupling optimization of network topology, cryptographic algorithms, and channel characteristics, improving the transmission reliability of PQC in dynamic satellite networks.

Description

Technical Field

[0001] This invention relates to the field of satellite communication and information security technology, and in particular to a secure transmission method for satellite constellation communication based on post-quantum cryptography. Background Technology

[0002] With the rapid development of Low Earth Orbit (LEO) satellite constellations, satellite communication networks are becoming a crucial infrastructure for seamless global coverage. However, the inherent openness of satellite links exposes them to severe security threats, while the rapid advancement of quantum computing poses a fundamental challenge to existing public-key cryptography systems. Therefore, integrating post-quantum cryptography (PQC), which is resistant to quantum attacks, into satellite communications has become an inevitable choice to ensure the long-term security of future space information networks.

[0003] However, the application of PQC in satellite constellation communication faces significant performance bottlenecks. Compared to traditional RSA or ECC algorithms, the public key, ciphertext, and signature sizes of PQC algorithms are generally more than an order of magnitude larger. For example, the NIST-standardized Dilithium digital signature can reach 2588 bytes, far exceeding the MTU of standard Ethernet (1500 bytes). This inevitably leads to IP fragmentation at the transport layer. Satellite communication channels themselves are characterized by high latency, high bit error rate, and dynamic time-varying links, especially in low-Earth orbit satellite scenarios where the available time window for satellite-to-ground links is extremely short (typically only a few minutes) and involves frequent switching. Studies have shown that in the event of sudden packet loss due to severe weather, the loss of a single fragment can lead to the retransmission of the entire PQC handshake data packet, with a handshake failure rate exceeding 50%. This not only severely impacts user experience but may even cause interruptions to satellite communication services.

[0004] Current technologies mainly focus on hardware acceleration of the PQC algorithm itself or hybrid encryption modes at the protocol layer. They have not solved the problem of reliable transmission of large PQC data packets in satellite channels with dynamic time-varying and extremely short available time windows. They have failed to jointly optimize the dynamic topology constraints of satellite networks, the non-stationary time-varying characteristics of channels, and the size characteristics of the PQC algorithm. As a result, the success rate of secure handshake cannot be guaranteed in scenarios with frequent link switching and tight available time windows. Summary of the Invention

[0005] The purpose of this invention is to provide a secure transmission method for satellite constellation communication based on post-quantum cryptography. By deeply coupling the dynamic topology constraints of the satellite, the algorithm characteristics of PQC, and the non-stationary characteristics of the channel, and generating an adaptive transmission strategy based on probabilistic constraints, the transmission reliability of PQC data packets in dynamic time-varying satellite channels is significantly improved.

[0006] To achieve the above objectives, this invention provides a secure transmission method for satellite constellation communication based on post-quantum cryptography, comprising the following steps: The system acquires the time-varying topology of the low-Earth orbit satellite constellation and the geographical location of the target ground station, determines the relative motion trajectory between the satellite and the target ground station, and calculates the expected duration of the satellite-to-ground link and the link switching time within the current time window based on the relative motion trajectory. The latency sensitivity level of the secure handshake is determined based on the expected duration; Based on the latency sensitivity level, a set of candidate algorithms is pre-selected from the post-quantum cryptography algorithm spectrum; the set of candidate algorithms has a protocol data unit size range that matches the latency sensitivity level. The channel state of the satellite-to-ground link is obtained, and characteristic parameters reflecting the non-stationary characteristics of the channel are extracted; the characteristic parameters include fading depth, fading duration, and Doppler rate of change. Based on the candidate algorithm set, a multi-dimensional joint optimization model is constructed according to the protocol data unit size range, feature parameters, and expected duration. Based on the multidimensional joint optimization model, an adaptive transmission strategy is generated that is adapted to the current latency sensitivity level and channel state; the adaptive transmission strategy includes: optimal algorithm identification strategy, optimal fragmentation granularity strategy, optimal redundancy strategy, and optimal modulation and coding strategy; The corresponding post-quantum cryptography protocol data unit is generated according to the optimal algorithm identification strategy. Based on the optimal granularity strategy and the optimal redundancy strategy, the post-quantum cryptography protocol data unit is adaptively non-uniformly sharded and encoded based on fountain codes to generate a data symbol stream with sequential dependencies. Based on the Doppler rate of change, the trend of satellite-to-ground link quality change is predicted, and the transmission priority and transmission time interval of the data symbol stream are dynamically adjusted based on the trend of change. The adjusted data symbol stream is then transmitted through the satellite communication link.

[0007] Preferably, the specific details of determining the latency sensitivity level of the secure handshake based on the expected duration include: Set a first time threshold and a second time threshold; the first time threshold is greater than the second time threshold. When the expected duration is greater than or equal to the first time threshold, it is judged as a low sensitivity level; When the expected duration is between the second time threshold and the first time threshold, it is judged as medium sensitivity level; When the expected duration is less than or equal to the second time threshold, it is judged as a high sensitivity level.

[0008] Preferably, the specific content of pre-screening the candidate algorithm set from the post-quantum cryptography algorithm spectrum based on the time delay sensitivity level includes: When the sensitivity level is determined to be low, high-security algorithms with protocol data unit sizes greater than or equal to the first size threshold are pre-selected. When the sensitivity level is determined to be medium, a balanced algorithm with protocol data unit sizes between the first and second size thresholds is pre-selected. When a high sensitivity level is determined, lightweight algorithms with protocol data unit sizes less than or equal to the second size threshold are pre-selected.

[0009] Preferably, based on the candidate algorithm set, and according to the protocol data unit size range, feature parameters, and expected duration, the specific content of constructing a multi-dimensional joint optimization model includes: The algorithm identifier, fragmentation granularity, fountain code redundancy, and physical layer modulation and coding scheme in the candidate algorithm set are defined as joint decision variables, and the value range of each variable is determined. Based on the fading depth and fading duration in the feature parameters, a state transition probability matrix describing the time-varying characteristics of the channel is constructed; Using joint decision variables as independent variables, an expected total time consumption function is established, which is composed of the coupling of computation delay, transmission delay, and retransmission delay; the retransmission delay is determined by recursion based on the state transition probability matrix and the degree distribution function of the fountain code. Using joint decision variables as constraints and expected duration as time boundary, construct probabilistic constraints. Within the defined range of values ​​for each variable, a multidimensional joint optimization problem with the objective of maximizing the success probability is solved, resulting in a multidimensional joint optimization model.

[0010] Preferably, the corresponding post-quantum cryptography protocol data unit is generated according to the optimal algorithm identification strategy, and the post-quantum cryptography protocol data unit is adaptively non-uniformly fragmented and encoded based on fountain codes according to the optimal fragmentation granularity strategy and the optimal redundancy strategy, generating a data symbol stream with sequential dependencies. The specific content includes: Generate the corresponding post-quantum cryptography protocol data unit according to the optimal algorithm identification strategy; The internal structure of the data units in the quantum cryptography protocol is analyzed to identify and label key and non-key segments. Based on the optimal fragmentation granularity strategy and the fading depth of the current channel, non-uniform fragmentation is performed on critical fragments and non-critical fragments to generate original fragment sets with different sizes and data importance. Based on the optimal redundancy strategy, the original fragment set is fountain-coded to generate coded symbols; Add header information containing sequence numbers to the encoded symbols to establish sequential dependencies between them and form an ordered data symbol stream; Assign a transmission priority label to the corresponding encoded symbol based on the importance level of the original fragment, and output the data symbol stream with the priority label to the transmission queue.

[0011] Preferably, based on the Doppler rate of change, the trend of satellite-to-ground link quality change is predicted, and the transmission priority and transmission time interval of the data symbol stream are dynamically adjusted based on the trend. The specific content of the adjusted data symbol stream transmitted through the satellite communication link includes: The Doppler change rate of the satellite-to-ground link is acquired in real time, and a first threshold and a second threshold are set to determine the changing trend of the satellite-to-ground link quality; the changing trend includes: improvement trend, deterioration trend and stable trend; Obtain the time margin between the current time and the link switching time, and determine whether the current satellite-to-ground link has entered the emergency transmission window; Based on the changing trend and the emergency transmission window determination results, priority remapping is performed on key data symbols and non-key data symbols in the data symbol stream; Based on the changing trend and the result of the emergency sending window determination, the sending time interval of the data symbol stream is dynamically adjusted; Based on the remapped priority and the adjusted transmission time interval, symbols are extracted from the transmission queue for scheduling, and an active packet loss strategy is executed when the queue is congested. The scheduled data symbol stream is transmitted via the satellite communication link according to the optimal modulation and coding strategy, and the transmission parameters are recorded.

[0012] Preferably, the specific content of determining the changing trend of the satellite-to-ground link quality includes: real-time acquisition of the Doppler change rate of the satellite-to-ground link, setting a first threshold and a second threshold. Real-time measurement of instantaneous Doppler frequency shift values ​​of the satellite-to-ground link; The Doppler rate of change is obtained by performing time difference calculation on the instantaneous Doppler frequency shift value; Based on satellite orbit parameters and link budget, a first threshold and a second threshold are preset; the first threshold is greater than zero, and the second threshold is less than zero; Compare the Doppler rate of change with the first threshold and the second threshold; If the Doppler rate of change is greater than or equal to the first threshold, the link quality is determined to be improving. If the Doppler rate of change is less than or equal to the first threshold, the link quality is determined to be deteriorating. If the Doppler rate of change is between the second threshold and the first threshold, the link quality is considered to be stable. A sliding window filtering mechanism is used to verify the consistency of the judgment results for multiple consecutive sampling periods, and the final trend judgment result is output.

[0013] Preferably, the specific steps for determining whether the current satellite-to-ground link has entered the emergency transmission window include obtaining the time slack between the current moment and the link switching moment: The current time is obtained through the onboard clock synchronization mechanism; Calculate the difference between the link switching time and the current time to obtain the time margin; the time margin is the remaining available transmission time from the current time until the link is interrupted. Set a urgency threshold and compare the time margin with the urgency threshold; If the time margin is less than or equal to the urgent threshold, the current satellite-to-ground link is determined to enter the emergency transmission window; If the time margin is greater than the urgent threshold, the current satellite-to-ground link is determined to enter the normal transmission window.

[0014] Preferably, the secure transmission method for satellite constellation communication based on post-quantum cryptography further includes: By triggering the reacquisition of the channel state of the satellite-to-ground link at the link switching moment, a multi-dimensional joint optimization model is constructed, and finally an adaptive transmission strategy adapted to the new link channel state is generated.

[0015] This invention also provides a secure satellite constellation communication transmission system based on post-quantum cryptography, used to implement the above-mentioned secure satellite constellation communication transmission method based on post-quantum cryptography, comprising: The data acquisition module is used to acquire the time-varying topology of the low-Earth orbit satellite constellation and the geographical location of the target ground station, determine the relative motion trajectory between the satellite and the target ground station, and calculate the expected duration of the satellite-to-ground link and the link switching time within the current time window based on the relative motion trajectory. The level determination module is used to determine the latency sensitivity level of the secure handshake based on the expected duration. An algorithm filtering module is used to pre-select a set of candidate algorithms from the post-quantum cryptography algorithm spectrum based on the latency sensitivity level; the set of candidate algorithms has a protocol data unit size range that matches the latency sensitivity level. The feature extraction module is used to obtain the channel state of the satellite-to-ground link and extract feature parameters that reflect the non-stationary characteristics of the channel; the feature parameters include fading depth, fading duration and Doppler rate of change; The model building module is used to construct a multi-dimensional joint optimization model based on the candidate algorithm set, according to the protocol data unit size range, feature parameters, and expected duration. The strategy generation module is used to generate an adaptive transmission strategy that adapts to the current latency sensitivity level and channel state based on a multi-dimensional joint optimization model. The adaptive transmission strategy includes: optimal algorithm identification strategy, optimal fragmentation granularity strategy, optimal redundancy strategy, and optimal modulation and coding strategy. The symbol stream generation module is used to generate corresponding post-quantum cryptography protocol data units according to the optimal algorithm identification strategy, and to perform adaptive non-uniform fragmentation and fountain code-based encoding on the post-quantum cryptography protocol data units according to the optimal fragmentation granularity strategy and the optimal redundancy strategy, so as to generate a data symbol stream with sequential dependency. The predictive transmission module is used to predict the changing trend of the satellite-to-ground link quality based on the Doppler change rate, and dynamically adjust the transmission priority and transmission time interval of the data symbol stream based on the changing trend, and transmit the adjusted data symbol stream through the satellite communication link.

[0016] In summary, the satellite constellation communication secure transmission method based on post-quantum cryptography provided by this invention offers the following advantages compared to traditional technologies: By using delay sensitivity grading and PQC algorithm pre-screening, the dynamic topology constraints of the satellite link are transformed into quantized time windows, avoiding handshake failures caused by selecting large-size algorithms within short time windows; through adaptive non-uniform fragmentation, critical fragments containing core handshake parameters are allocated smaller sizes and higher protection levels, achieving differentiated protection based on data importance awareness; the constructed multi-dimensional joint optimization model overcomes the limitations of traditional hierarchical design, characterizing the time-varying characteristics of the channel through the channel state transition matrix and establishing a recursive relationship for retransmission delay through the fountain code distribution function, achieving full-link parameter coupling optimization from data packet generation to reliable data packet arrival; by extracting parameters reflecting the non-stationary characteristics of the channel, such as the Doppler rate of change, the trend of link quality changes is predicted; and a complete and engineerable secure transmission solution for future large-scale low-Earth orbit satellite constellations to resist quantum computing attacks is provided, possessing significant strategic importance and industrial application value.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a flowchart of a secure transmission method for satellite constellation communication based on post-quantum cryptography, as described in this invention. Figure 2 This is a block diagram of a satellite constellation secure transmission system based on post-quantum cryptography, as described in this invention. Detailed Implementation

[0019] The technical method of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application.

[0020] The following description of at least one exemplary embodiment is merely illustrative and is not intended to limit the scope of this application or its application or use.

[0021] Techniques, systems, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the instruction manual.

[0022] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0024] This invention provides a secure transmission method for satellite constellation communication based on post-quantum cryptography, such as... Figure 1 As shown, it includes the following steps: S1. Obtain the time-varying topology of the low-Earth orbit satellite constellation and the geographical location of the target ground station, determine the relative motion trajectory between the satellite and the target ground station, and calculate the expected duration of the satellite-to-ground link and the link switching time within the current time window based on the relative motion trajectory.

[0025] S2. Determine the latency sensitivity level of the secure handshake based on the expected duration.

[0026] Furthermore, step S2 specifically includes the following steps: S201, Set a first time threshold and a second time threshold; the first time threshold is greater than the second time threshold.

[0027] S202. When the expected duration is greater than or equal to the first time threshold, it is judged as a low sensitivity level.

[0028] S203. When the expected duration is between the second time threshold and the first time threshold, it is determined to be of medium sensitivity level.

[0029] S204. When the expected duration is less than or equal to the second time threshold, it is judged as a high sensitivity level.

[0030] This invention transforms dynamic network topology into time constraints for security protocols, providing a time benchmark for subsequent parameter optimization.

[0031] In an exemplary embodiment of the present invention, the time-varying topology of the low-Earth orbit (LEO) satellite constellation and the geographical location of the target ground station are obtained, and the relative motion trajectory between the LEO satellite constellation and the target ground station is calculated. Based on the relative motion trajectory, the available time window for the satellite-to-ground link between the LEO satellite constellation and the target ground station within the current overpass cycle is 85 seconds. A first time threshold is set to 120 seconds, and a second time threshold is set to 60 seconds. Since the second time threshold of 60 seconds is less than the available time window of 85 seconds and less than the first time threshold of 120 seconds, the latency sensitivity level of this security handshake is determined to be medium sensitivity. This level information will be sent to the LEO satellite constellation as a time constraint for subsequent parameter optimization.

[0032] S3. Based on the latency sensitivity level, a candidate algorithm set is pre-selected from the post-quantum cryptography algorithm spectrum. The candidate algorithm set has a protocol data unit size range that matches the latency sensitivity level.

[0033] Furthermore, step S3 specifically includes the following steps: S301. When the sensitivity level is determined to be low, a high-security algorithm with a protocol data unit size greater than or equal to the first size threshold is pre-selected.

[0034] S302. When the sensitivity level is determined to be medium, a balanced algorithm with protocol data unit size between the first size threshold and the second size threshold is pre-selected.

[0035] S303. When the sensitivity level is determined to be high, lightweight algorithms with protocol data unit sizes less than or equal to the second size threshold are pre-selected.

[0036] This invention achieves an initial match between the algorithm size and the available time window, thus reducing the search space for subsequent optimizations.

[0037] In an exemplary embodiment of the present invention, a pre-screening process is performed from the PQC algorithm family based on the determined medium sensitivity level. The system in this embodiment pre-stores a PQC algorithm database containing performance parameters for various algorithms. For the medium sensitivity level, the screening rule is: select balanced algorithms whose protocol data unit size is between a first size threshold of 1000 bytes and a second size threshold of 2000 bytes. The screening results generate a candidate algorithm set A. candidate ={Falcon-512(858B),Dilithium-3(2588B)}. Among them, although the Dilithium-3 algorithm exceeds the size limit, it may still be possible to complete the transmission through optimization under certain channel conditions, so it is retained in the candidate set for further consideration by the model.

[0038] S4. Obtain the channel state of the satellite-to-ground link and extract characteristic parameters reflecting the non-stationary characteristics of the channel. These characteristic parameters include fading depth, fading duration, and Doppler rate of change. These parameters describe the instantaneous state and trend of channel quality, providing a basis for predictive scheduling.

[0039] In an exemplary embodiment of the present invention, at a certain moment, it is sensed that the channel is in a deep fading state, specifically the fading depth. d The fading duration is 15 dB. τ The Doppler rate of change is 0.5s. f The value is -20 Hz / s. A negative Doppler rate of change indicates that the satellite is moving away from the target ground station, and the link quality is deteriorating.

[0040] S5. Based on the candidate algorithm set, construct a multi-dimensional joint optimization model according to the protocol data unit size range, feature parameters and expected duration.

[0041] Furthermore, step S5 is replaced by the following steps: S501. Define the algorithm identifier, fragmentation granularity, fountain code redundancy, and physical layer modulation and coding scheme in the candidate algorithm set as joint decision variables, and determine the value range of each variable.

[0042] S502. Based on the fading depth and fading duration in the characteristic parameters, construct a state transition probability matrix that describes the time-varying characteristics of the channel.

[0043] S503. Using the joint decision variables as independent variables, establish the expected total time consumption function, which is composed of the coupling of computation delay, transmission delay, and retransmission delay. The retransmission delay is determined through a recursive relationship based on the state transition probability matrix and the degree distribution function of the fountain code.

[0044] S504. Construct probabilistic constraints with joint decision variables as the constraint objects and expected duration as the time boundary.

[0045] S505. Within the defined range of values ​​for each variable, solve the multidimensional joint optimization problem with the objective of maximizing the success probability to obtain the multidimensional joint optimization model.

[0046] The multidimensional joint optimization model constructed in this invention performs cross-layer joint optimization of the cryptographic algorithm selection of the application layer, the fragmentation and coding of the link layer, and the modulation and coding scheme of the physical layer.

[0047] In an exemplary embodiment of the present invention, the multidimensional joint optimization model solution unit receives the latency sensitivity level (medium sensitivity), the candidate algorithm set, and the fading depth. d The fading duration is 15 dB. τ The Doppler rate of change is 0.5s.f A multi-dimensional joint optimization model is constructed for the channel characteristic parameters of -20Hz / s.

[0048] The objective function of the multidimensional joint optimization model is to maximize the probability of completing a secure handshake within 85 seconds. Decision variables include: algorithm identifier. a ∈A candidate Piece granularity g (How many pieces of data are divided into), fountain code redundancy r (Proportion of redundant symbols sent), modulation and coding scheme mcs (Determines the transmission rate and robustness of each symbol).

[0049] The core of the multidimensional joint optimization model is to calculate the expected total time consumption function T. total It consists of three coupled parts: Calculate the delay T comp The value is determined by the computational complexity of the selected PQC algorithm and can be obtained through offline measurement.

[0050] Transmission delay T trans Symbol transmission time is determined by the total data size, fragmentation granularity, and modulation and coding scheme.

[0051] Retransmission delay T retx Based on fading depth and duration, a channel state transition probability matrix for two states (good state / bad state) is constructed. Combining the degree distribution function of the fountain code, a recursive relationship between decoding failure probability and redundancy and channel state is established. The retransmission delay is the expected additional waiting time represented by this recursive relationship.

[0052] Solve the multidimensional joint optimization model. For the Falcon-512 algorithm, whose data size of 858B is relatively small, the optimal parameters are obtained by solving the multidimensional joint optimization model under a given channel condition: optimal fragmentation granularity. g The optimal redundancy is 4. r The optimal modulation and coding scheme is 0.3. mcs It is determined to be Quadrature Phase Shift Keying (QPSK), with the corresponding probability P(T) total ≤85) is 0.995. For the Dilithium-3 algorithm, its data size of 2588B is relatively large. Although it has higher security, under the current trend of channel degradation, it requires a larger redundancy r of 0.8 to combat packet loss, resulting in excessively long transmission time. The calculated probability P(T) is... total ≤85) is 0.82. Therefore, the multidimensional joint optimization model ultimately selects the Falcon-512 algorithm and outputs an adaptive transmission strategy, i.e., the optimal algorithm identifier. aFor Falcon-512, the optimal fragmentation granularity is... g The optimal redundancy is 4. r The optimal modulation and coding scheme is 0.3. mcs It has been confirmed as QPSK.

[0053] S6. Based on the multi-dimensional joint optimization model, generate an adaptive transmission strategy that adapts to the current delay sensitivity level and channel state. The adaptive transmission strategy includes: optimal algorithm identification strategy, optimal fragmentation granularity strategy, optimal redundancy strategy, and optimal modulation and coding strategy.

[0054] S7. Generate the corresponding post-quantum cryptography protocol data unit according to the optimal algorithm identification strategy, and perform adaptive non-uniform fragmentation and fountain code-based encoding on the post-quantum cryptography protocol data unit according to the optimal fragmentation granularity strategy and the optimal redundancy strategy to generate a data symbol stream with sequential dependency relationship.

[0055] Furthermore, step S7 specifically includes the following steps: S701. Generate the corresponding post-quantum cryptography protocol data unit according to the optimal algorithm identification strategy.

[0056] S702. Decipher the internal structure of the quantum cryptography protocol data unit, identify and label key and non-key segments.

[0057] S703. Based on the optimal fragmentation granularity strategy and the fading depth of the current channel, perform non-uniform fragmentation on critical and non-critical fragments to generate an original fragment set with different sizes and data importance.

[0058] S704. Based on the optimal redundancy strategy, perform fountain code encoding on the original fragment set to generate encoded symbols.

[0059] S705. Add header information containing sequence numbers to the encoded symbols to establish sequential dependencies between encoded symbols and form an ordered data symbol stream.

[0060] S706. Assign a transmission priority label to the corresponding encoded symbol according to the importance level of the original fragment, and output the data symbol stream with the priority label to the transmission queue.

[0061] In an exemplary embodiment of the present invention, the satellite identifies Falcon-512 using the optimal algorithm and generates a corresponding post-quantum cryptography protocol data unit (including certificate, signature, etc.), with a total size of 858 bytes. This is based on the optimal fragmentation granularity. g =4 and redundancy r =0.3, adaptive non-uniform fragmentation and fountain code encoding are performed on the data units.

[0062] S8. Based on the Doppler rate of change, predict the trend of changes in the quality of the satellite-to-ground link, and dynamically adjust the transmission priority and transmission time interval of the data symbol stream based on the trend of changes, and transmit the adjusted data symbol stream through the satellite communication link.

[0063] Furthermore, step S8 is replaced by the following steps: S801. Real-time acquisition of the Doppler change rate of the satellite-to-ground link, and setting a first threshold and a second threshold to determine the changing trend of the satellite-to-ground link quality. The changing trend includes: improving trend, deteriorating trend, and stable trend.

[0064] Specifically, step S801 includes the following: Real-time measurement of instantaneous Doppler frequency shift value of satellite-to-ground link.

[0065] The Doppler rate of change is obtained by performing time difference calculation on the instantaneous Doppler frequency shift value.

[0066] Based on satellite orbit parameters and link budget, a first threshold and a second threshold are preset. The first threshold is greater than zero, and the second threshold is less than zero.

[0067] The Doppler rate of change is compared with the first threshold and the second threshold.

[0068] If the Doppler change rate is greater than or equal to the first threshold, the link quality is considered to be improving.

[0069] If the Doppler rate of change is less than or equal to the first threshold, the link quality is determined to be deteriorating.

[0070] If the Doppler rate of change is between the second threshold and the first threshold, the link quality is considered to be stable.

[0071] A sliding window filtering mechanism is used to verify the consistency of the judgment results for multiple consecutive sampling periods, and the final trend judgment result is output.

[0072] S802. Obtain the time slack between the current time and the link switching time, and determine whether the current satellite-to-ground link has entered the emergency transmission window.

[0073] Specifically, step S802 includes the following: The current time is obtained through the onboard clock synchronization mechanism.

[0074] Calculate the difference between the link switching time and the current time to obtain the time margin. The time margin is the remaining available transmission time from the current time until the link is interrupted.

[0075] Set a urgency threshold and compare the time margin with the urgency threshold.

[0076] If the time margin is less than or equal to the urgent threshold, the current satellite-to-ground link is determined to have entered the emergency transmission window.

[0077] If the time margin is greater than the urgent threshold, the current satellite-to-ground link is determined to enter the normal transmission window.

[0078] S803. Based on the trend of change and the result of the emergency transmission window, priority remapping is performed on the key data symbols and non-key data symbols in the data symbol stream.

[0079] S804. Based on the changing trend and the result of the emergency sending window determination, dynamically adjust the sending time interval of the data symbol stream.

[0080] S805. Based on the remapped priority and the adjusted transmission time interval, extract symbols from the transmission queue for scheduling, and execute an active packet loss strategy when the queue is congested.

[0081] S806. The scheduled data symbol stream is transmitted through the satellite communication link according to the optimal modulation and coding strategy, and the transmission parameters are recorded.

[0082] In an exemplary embodiment of the present invention, the secure transmission method for satellite constellation communication based on post-quantum cryptography further includes: By triggering the reacquisition of the channel state of the satellite-to-ground link at the link switching moment, a multi-dimensional joint optimization model is constructed, and finally an adaptive transmission strategy adapted to the new link channel state is generated.

[0083] This invention transforms the dynamic topology constraints of satellite links into quantized time windows through latency sensitivity grading and PQC algorithm pre-screening, avoiding handshake failures caused by selecting large-size algorithms within short time windows. By replacing traditional IP fragmentation with fountain code encoding, the receiver only needs to receive a sufficient number of symbols to recover complete data, significantly improving resilience against burst packet loss. Adaptive non-uniform fragmentation allocates smaller sizes and higher protection levels to critical fragments containing core handshake parameters, achieving differentiated protection based on data importance. The multi-dimensional joint optimization model constructed in this invention overcomes the limitations of traditional layered designs, using application-layer algorithm selection, link-layer fragmentation granularity and redundancy, and physical-layer modulation and coding schemes as joint decision variables, with the objective function being to maximize the probability of completing the handshake within the expected duration. The multi-dimensional joint optimization model characterizes the time-varying characteristics of the channel through the channel state transition matrix and establishes a recursive relationship for retransmission delay through the fountain code distribution function, achieving end-to-end parameter coupling optimization from "data packet generation" to "reliable data packet arrival." Furthermore, this invention achieves prediction of link quality change trends by extracting parameters such as the Doppler change rate that reflect the non-stationary characteristics of the channel—when the Doppler change rate is positive, it is determined that the channel is about to improve, and when it is negative, it is determined that the channel is about to deteriorate; combined with the time margin determination at the link switching time, the transmission priority and transmission interval of data symbols are dynamically adjusted.

[0084] This invention also provides a secure satellite constellation communication transmission system based on post-quantum cryptography, used to implement the aforementioned secure satellite constellation communication transmission method based on post-quantum cryptography, such as... Figure 2 As shown, it includes: The data acquisition module is used to acquire the time-varying topology of the low-Earth orbit satellite constellation and the geographical location of the target ground station, determine the relative motion trajectory between the satellite and the target ground station, and calculate the expected duration of the satellite-to-ground link and the link switching time within the current time window based on the relative motion trajectory.

[0085] The level determination module is used to determine the latency sensitivity level of the secure handshake based on the expected duration.

[0086] The algorithm selection module is used to pre-select a set of candidate algorithms from the post-quantum cryptography algorithm spectrum based on latency sensitivity levels. The candidate algorithm set has a protocol data unit size range that matches the latency sensitivity level.

[0087] The feature extraction module is used to acquire the channel state of the satellite-to-ground link and extract feature parameters that reflect the non-stationary characteristics of the channel. These feature parameters include fading depth, fading duration, and Doppler rate of change.

[0088] The model building module is used to construct a multi-dimensional joint optimization model based on the candidate algorithm set, according to the protocol data unit size range, feature parameters, and expected duration.

[0089] The strategy generation module is used to generate adaptive transmission strategies that are adapted to the current latency sensitivity level and channel state based on a multi-dimensional joint optimization model. These adaptive transmission strategies include: optimal algorithm identification strategy, optimal fragmentation granularity strategy, optimal redundancy strategy, and optimal modulation and coding strategy.

[0090] The symbol stream generation module is used to generate corresponding post-quantum cryptography protocol data units according to the optimal algorithm identification strategy, and to perform adaptive non-uniform fragmentation and fountain code-based encoding on the post-quantum cryptography protocol data units according to the optimal fragmentation granularity strategy and the optimal redundancy strategy, thereby generating a data symbol stream with sequential dependencies.

[0091] The predictive transmission module is used to predict the changing trend of the satellite-to-ground link quality based on the Doppler change rate, and dynamically adjust the transmission priority and transmission time interval of the data symbol stream based on the changing trend, and transmit the adjusted data symbol stream through the satellite communication link.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A secure transmission method for satellite constellation communication based on post-quantum cryptography, characterized in that, Includes the following steps: The system acquires the time-varying topology of the low-Earth orbit satellite constellation and the geographical location of the target ground station, determines the relative motion trajectory between the satellite and the target ground station, and calculates the expected duration of the satellite-to-ground link and the link switching time within the current time window based on the relative motion trajectory. The latency sensitivity level of the secure handshake is determined based on the expected duration; Based on the latency sensitivity level, a set of candidate algorithms is pre-selected from the post-quantum cryptography algorithm spectrum; the set of candidate algorithms has a protocol data unit size range that matches the latency sensitivity level. The channel state of the satellite-to-ground link is obtained, and characteristic parameters reflecting the non-stationary characteristics of the channel are extracted; the characteristic parameters include fading depth, fading duration, and Doppler rate of change. Based on the candidate algorithm set, a multi-dimensional joint optimization model is constructed according to the protocol data unit size range, feature parameters, and expected duration. Based on the multidimensional joint optimization model, an adaptive transmission strategy is generated that is adapted to the current latency sensitivity level and channel state; the adaptive transmission strategy includes: optimal algorithm identification strategy, optimal fragmentation granularity strategy, optimal redundancy strategy, and optimal modulation and coding strategy; The corresponding post-quantum cryptography protocol data unit is generated according to the optimal algorithm identification strategy. Based on the optimal granularity strategy and the optimal redundancy strategy, the post-quantum cryptography protocol data unit is adaptively non-uniformly sharded and encoded based on fountain codes to generate a data symbol stream with sequential dependencies. Based on the Doppler rate of change, the trend of satellite-to-ground link quality change is predicted, and the transmission priority and transmission time interval of the data symbol stream are dynamically adjusted based on the trend of change. The adjusted data symbol stream is then transmitted through the satellite communication link.

2. The secure transmission method for satellite constellation communication based on post-quantum cryptography according to claim 1, characterized in that, The specific details for determining the latency sensitivity level of a secure handshake based on its expected duration include: Set a first time threshold and a second time threshold; the first time threshold is greater than the second time threshold. When the expected duration is greater than or equal to the first time threshold, it is judged as a low sensitivity level; When the expected duration is between the second time threshold and the first time threshold, it is judged as medium sensitivity level; When the expected duration is less than or equal to the second time threshold, it is judged as a high sensitivity level.

3. The secure transmission method for satellite constellation communication based on post-quantum cryptography according to claim 2, characterized in that, Based on latency sensitivity levels, the specific content of the candidate algorithm set pre-screened from the post-quantum cryptography algorithm spectrum includes: When the sensitivity level is determined to be low, high-security algorithms with protocol data unit sizes greater than or equal to the first size threshold are pre-selected. When the sensitivity level is determined to be medium, a balanced algorithm with protocol data unit sizes between the first and second size thresholds is pre-selected. When a high sensitivity level is determined, lightweight algorithms with protocol data unit sizes less than or equal to the second size threshold are pre-selected.

4. The secure transmission method for satellite constellation communication based on post-quantum cryptography according to claim 1, characterized in that, Based on the candidate algorithm set, the specific content of constructing a multi-dimensional joint optimization model according to the protocol data unit size range, feature parameters, and expected duration includes: The algorithm identifier, fragmentation granularity, fountain code redundancy, and physical layer modulation and coding scheme in the candidate algorithm set are defined as joint decision variables, and the value range of each variable is determined. Based on the fading depth and fading duration in the feature parameters, a state transition probability matrix describing the time-varying characteristics of the channel is constructed; Using joint decision variables as independent variables, an expected total time consumption function is established, which is composed of the coupling of computation delay, transmission delay, and retransmission delay; the retransmission delay is determined by recursion based on the state transition probability matrix and the degree distribution function of the fountain code. Using joint decision variables as constraints and expected duration as time boundary, construct probabilistic constraints. Within the defined range of values ​​for each variable, a multidimensional joint optimization problem with the objective of maximizing the success probability is solved, resulting in a multidimensional joint optimization model.

5. A secure transmission method for satellite constellation communication based on post-quantum cryptography according to claim 1, characterized in that, Based on the optimal algorithm identification strategy, corresponding post-quantum cryptography protocol data units are generated. Then, based on the optimal granularity and redundancy strategies, adaptive non-uniform sharding and fountain code-based encoding are performed on the post-quantum cryptography protocol data units to generate a data symbol stream with sequential dependencies. The specific content includes: Generate the corresponding post-quantum cryptography protocol data unit according to the optimal algorithm identification strategy; The internal structure of the data units in the quantum cryptography protocol is analyzed to identify and label key and non-key segments. Based on the optimal fragmentation granularity strategy and the fading depth of the current channel, non-uniform fragmentation is performed on critical fragments and non-critical fragments to generate original fragment sets with different sizes and data importance. Based on the optimal redundancy strategy, the original fragment set is fountain-coded to generate coded symbols; Add header information containing sequence numbers to the encoded symbols to establish sequential dependencies between them and form an ordered data symbol stream; Assign a transmission priority label to the corresponding encoded symbol based on the importance level of the original fragment, and output the data symbol stream with the priority label to the transmission queue.

6. A secure transmission method for satellite constellation communication based on post-quantum cryptography according to claim 5, characterized in that, Based on the Doppler rate of change, the trend of satellite-to-ground link quality variation is predicted, and the transmission priority and transmission interval of the data symbol stream are dynamically adjusted based on the trend. The specific content of the adjusted data symbol stream transmitted through the satellite communication link includes: The Doppler change rate of the satellite-to-ground link is acquired in real time, and a first threshold and a second threshold are set to determine the changing trend of the satellite-to-ground link quality; the changing trend includes: improvement trend, deterioration trend and stable trend; Obtain the time margin between the current time and the link switching time, and determine whether the current satellite-to-ground link has entered the emergency transmission window; Based on the changing trend and the emergency transmission window determination results, priority remapping is performed on key data symbols and non-key data symbols in the data symbol stream; Based on the changing trend and the result of the emergency sending window determination, the sending time interval of the data symbol stream is dynamically adjusted; Based on the remapped priority and the adjusted transmission time interval, symbols are extracted from the transmission queue for scheduling, and an active packet loss strategy is executed when the queue is congested. The scheduled data symbol stream is transmitted via the satellite communication link according to the optimal modulation and coding strategy, and the transmission parameters are recorded.

7. A secure transmission method for satellite constellation communication based on post-quantum cryptography according to claim 6, characterized in that, The specific content of determining the changing trend of satellite-to-ground link quality includes: real-time acquisition of Doppler variation rate of satellite-to-ground link, setting first and second thresholds, and determining the changing trend of satellite-to-ground link quality. Real-time measurement of instantaneous Doppler frequency shift values ​​of the satellite-to-ground link; The Doppler rate of change is obtained by performing time difference calculation on the instantaneous Doppler frequency shift value; Based on satellite orbit parameters and link budget, a first threshold and a second threshold are preset; the first threshold is greater than zero, and the second threshold is less than zero; Compare the Doppler rate of change with the first threshold and the second threshold; If the Doppler rate of change is greater than or equal to the first threshold, the link quality is determined to be improving. If the Doppler rate of change is less than or equal to the first threshold, the link quality is determined to be deteriorating. If the Doppler rate of change is between the second threshold and the first threshold, the link quality is considered to be stable. A sliding window filtering mechanism is used to verify the consistency of the judgment results for multiple consecutive sampling periods, and the final trend judgment result is output.

8. A secure transmission method for satellite constellation communication based on post-quantum cryptography according to claim 7, characterized in that, The specific steps for determining whether the current satellite-to-ground link has entered the emergency transmission window include obtaining the time slack between the current time and the link switching time. The current time is obtained through the onboard clock synchronization mechanism; Calculate the difference between the link switching time and the current time to obtain the time margin; the time margin is the remaining available transmission time from the current time until the link is interrupted. Set a urgency threshold and compare the time margin with the urgency threshold; If the time margin is less than or equal to the urgent threshold, the current satellite-to-ground link is determined to enter the emergency transmission window; If the time margin is greater than the urgent threshold, the current satellite-to-ground link is determined to enter the normal transmission window.

9. A secure transmission method for satellite constellation communication based on post-quantum cryptography according to claim 8, characterized in that, The secure transmission method for satellite constellation communication based on post-quantum cryptography also includes: By triggering the reacquisition of the channel state of the satellite-to-ground link at the link switching moment, a multi-dimensional joint optimization model is constructed, and finally an adaptive transmission strategy adapted to the new link channel state is generated.

10. A secure satellite constellation communication transmission system based on post-quantum cryptography, characterized in that, A method for implementing secure satellite constellation communication based on post-quantum cryptography as described in any one of claims 1-9 includes: The data acquisition module is used to acquire the time-varying topology of the low-Earth orbit satellite constellation and the geographical location of the target ground station, determine the relative motion trajectory between the satellite and the target ground station, and calculate the expected duration of the satellite-to-ground link and the link switching time within the current time window based on the relative motion trajectory. The level determination module is used to determine the latency sensitivity level of the secure handshake based on the expected duration. An algorithm filtering module is used to pre-select a set of candidate algorithms from the post-quantum cryptography algorithm spectrum based on the latency sensitivity level; the set of candidate algorithms has a protocol data unit size range that matches the latency sensitivity level. The feature extraction module is used to obtain the channel state of the satellite-to-ground link and extract feature parameters that reflect the non-stationary characteristics of the channel; the feature parameters include fading depth, fading duration and Doppler rate of change; The model building module is used to construct a multi-dimensional joint optimization model based on the candidate algorithm set, according to the protocol data unit size range, feature parameters, and expected duration. The strategy generation module is used to generate an adaptive transmission strategy that adapts to the current latency sensitivity level and channel state based on a multi-dimensional joint optimization model. The adaptive transmission strategy includes: optimal algorithm identification strategy, optimal fragmentation granularity strategy, optimal redundancy strategy, and optimal modulation and coding strategy. The symbol stream generation module is used to generate corresponding post-quantum cryptography protocol data units according to the optimal algorithm identification strategy, and to perform adaptive non-uniform fragmentation and fountain code-based encoding on the post-quantum cryptography protocol data units according to the optimal fragmentation granularity strategy and the optimal redundancy strategy, so as to generate a data symbol stream with sequential dependency. The predictive transmission module is used to predict the changing trend of the satellite-to-ground link quality based on the Doppler change rate, and dynamically adjust the transmission priority and transmission time interval of the data symbol stream based on the changing trend, and transmit the adjusted data symbol stream through the satellite communication link.

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