A secure spread spectrum communication method and system based on stream encryption

Abstract

This invention belongs to the field of secure communication technology and discloses a secure spread spectrum communication method based on stream encryption. The invention includes a pre-encryption module, a constellation shaping module, a higher-order mapping module, a spread spectrum modulation module, a randomization module, and an editing module. The original binary data signal (I / O) is sent to the pre-encryption module for processing. The input of the constellation shaping module is connected to its output. The input of the higher-order mapping module is connected to its output. The first output of the higher-order mapping module is connected to the editing module, and its second output is connected to the first input of the spread spectrum modulation module. The second input of the spread spectrum modulation module is connected to the output of the editing module. The randomization module is connected to the output of the spread spectrum modulation module. This invention achieves strict data confidentiality through the interaction between the modules, significantly reducing the probability of detection by non-cooperative parties, and its structure is simple and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of secure communication technology, and in particular relates to a secure spread spectrum communication method and system based on stream encryption. Background Technology

[0002] Direct sequence spread spectrum (DSSS) technology is widely used in secure communications due to its strong anti-interference capability and low power spectral density. Traditional DSSS signals spread the signal spectrum by multiplying a high-bit-rate pseudo-random (PN) sequence with low-bit-rate information data, and the receiver uses the same spreading sequence to perform despreading.

[0003] This secure communication method, widely adopted in military, commercial, and civilian applications, is vulnerable to malicious attacks based on cyclic detection. Because the signal formation process repeats and uses the same spreading sequence, the signal can be detected and its features extracted even in extremely harsh environments using blind processing methods. This not only renders energy-level stealth signals undetectable under cyclic attacks but also allows eavesdroppers to reconstruct the spreading sequence and decipher the signal. The widely accepted low probability of interception and high security of spread spectrum signals are being gradually eroded by their inherent cyclic nature.

[0004] To reduce the cyclic characteristics of spread spectrum signals and improve security, randomization techniques are introduced. These include introducing discrete chaos for spread spectrum chip encryption, introducing random Gaussian noise to modulate the spread spectrum signal to hide cyclic features, introducing jitter or randomized length to eliminate chip features, and randomizing the spread spectrum sequence to eliminate periodic features.

[0005] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0006] (1) Stringent application conditions. Encrypting a single chip or randomizing its length to eliminate cyclic characteristics requires the receiver to perform a reverse operation to recover the data. This often means that high synchronization requirements are needed, which is difficult to achieve in spread spectrum application scenarios.

[0007] (2) The computational workload is enormous. For each bit signal, a non-repeating spreading code is used for transmission, which requires the receiver to repeatedly perform despreading operations based on the possible spreading codes.

[0008] (3) Limited confidentiality of historical content. The confidentiality of existing technologies still relies on the cross-correlation properties of spreading codes. Only by protecting the security of the code can the signal content be maintained. This means that when the code is leaked or when faced with more advanced blind processing methods, not only is the current signal content threatened, but the information security of historically transmitted content cannot be guaranteed. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a secure spread spectrum communication method based on stream encryption.

[0010] This invention is implemented as follows: A secure spread spectrum communication method based on stream encryption includes:

[0011] Step 1: Perform XOR encryption on the input binary data to obtain an encrypted binary sequence;

[0012] Step 2: Perform probability amplitude shaping on the encrypted binary sequence to generate a constellation symbol sequence with a preset probability distribution;

[0013] Step 3: Perform high-order constellation mapping processing on the constellation symbol sequence to generate high-order modulation symbols and output two data paths, wherein the first data path is used to generate spread spectrum sequence control information and the second data path is used for spread spectrum modulation input;

[0014] Step 4: Generate the corresponding spreading sequence based on the spreading sequence control information;

[0015] Step 5: Perform spread spectrum modulation processing based on the spread spectrum sequence and the higher-order modulation symbols;

[0016] Step 6: Randomize the spread spectrum modulation result to obtain a spread spectrum signal with suppressed features.

[0017] Furthermore, the probability amplitude shaping is achieved through a constant constant combination distribution matching method, and the sign probability distribution is determined based on the exponential function of the square of the constellation point amplitude.

[0018] Furthermore, the XOR encryption process generates a binary ciphertext sequence by performing a bitwise XOR operation between the binary plaintext sequence and the binary key sequence.

[0019] Furthermore, the higher-order constellation mapping process forms higher-order modulation symbols by appending an encryption base sequence to the tail of the binary symbols corresponding to the constellation points.

[0020] Another objective of this invention is to provide a secure spread spectrum communication method based on stream encryption, comprising the following steps:

[0021] Obtain the control data output by the higher-order constellation mapping module;

[0022] Edit the spread spectrum sequence based on the control data;

[0023] Select the corresponding spreading sequence based on the higher-order modulation symbols;

[0024] Spread spectrum modulation is performed on the spread spectrum sequence and higher-order modulation symbols to generate a spread spectrum signal;

[0025] Randomization processing is performed on the spread spectrum signal to generate a random spread spectrum sequence.

[0026] Furthermore, the randomization process is achieved by performing random rotations on the spread spectrum sequence in the vector space.

[0027] Furthermore, after the randomization process, the random sequence is fitted using a fixed number of chips of unequal length.

[0028] Another object of the present invention is to provide a secure spread spectrum communication system based on stream encryption, comprising:

[0029] The pre-encryption module is used to perform XOR encryption on the input binary data;

[0030] The constellation shaping module is used to perform probability amplitude shaping on the encrypted binary sequence;

[0031] The higher-order mapping module is used to perform higher-order constellation mapping on the constellation shaping output and output two data streams.

[0032] The editing module is used to generate spread spectrum sequences based on the output of the higher-order mapping module;

[0033] The spread spectrum modulation module is used to perform spread spectrum modulation based on the spread spectrum sequence and higher-order modulation symbols;

[0034] The randomization module is used to perform randomization processing on the spread spectrum modulation results and output the spread spectrum signal.

[0035] Furthermore, the constellation shaping module employs a constant constant combination distribution matching structure to achieve probability amplitude shaping.

[0036] Furthermore, the keys used by the pre-encryption module and the higher-order mapping module are shared between the sender and receiver via a private communication channel.

[0037] Based on the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solution to be protected by this invention from the following aspects:

[0038] To address the long-standing security and detectability issues in spread spectrum communication systems, this technical solution introduces stream encryption, probability amplitude shaping, higher-order mapping, and randomized spreading mechanisms into the spread spectrum communication structure. This constructs a signal generation method with multi-layered security characteristics, effectively solving the security risks inherent in traditional spread spectrum communication's reliance on the confidentiality of the spreading sequence. In existing spread spectrum communication systems, the spreading sequence is typically considered a core security resource. Once the spreading code is obtained or deduced by a third party, the communication signal may be identified or even despread, leading to information leakage. Furthermore, because spreading sequences often have a fixed periodic structure, their cyclic characteristics are quite evident in signal statistical properties, allowing third parties to identify the spread spectrum signal using techniques such as cyclic spectrum analysis and cyclic correlation detection. This significantly reduces the stealth of the communication system in complex electromagnetic environments or adversarial communication scenarios. To address these technical problems, this solution introduces a multi-layered collaborative mechanism during signal generation. First, by performing stream encryption on the input data, the original information is initially encrypted before entering the modulation stage, forming an encryption sequence associated with the key. This tightly links the signal structure with the key, ensuring that even if the spread spectrum sequence is obtained, a third party cannot directly recover the original data. Second, probability amplitude shaping optimizes the constellation symbol distribution, making the modulation symbols exhibit a non-uniform probability distribution. This reduces the regularity of the signal's statistical characteristics, improves signal power utilization efficiency, and makes the signal characteristics closer to a random distribution. Subsequently, a higher-order mapping mechanism embeds the encryption base information into the modulation symbol structure, coupling the signal modulation process with the encryption information, thereby further increasing the signal structure complexity. Simultaneously, a spread spectrum sequence editing mechanism allows the spread spectrum sequence to dynamically change according to the input data, freeing the spread spectrum signal from dependence on a fixed spreading code structure. Finally, randomization is applied to the spread spectrum signal through random vector space rotation and chip reconstruction, resulting in a more uniform random distribution in both the time and frequency domains. Through the synergistic effect of the aforementioned multi-layered technical mechanisms, even if the spread spectrum sequence is leaked, the communication system can still maintain data security, and the cyclic statistical characteristics of the spread spectrum signal are significantly suppressed, thereby effectively reducing the possibility of third parties identifying the spread spectrum signal through cyclic detection methods. Compared with traditional spread spectrum communication systems, this technical solution achieves significant improvements in security, anti-detection capabilities, and signal concealment, providing a new implementation path for spread spectrum communication security mechanisms, and possessing significant technological advancements and engineering application value.

[0039] Does the technical solution of this invention overcome technical bias? In traditional communication theory, the industry generally believes that probabilistic shaping technology exists only as a means to approach the Shannon channel capacity limit and improve transmission efficiency. This invention breaks this inherent perception, innovatively combining shaping technology with spread spectrum communication and stream encryption mechanisms. It utilizes non-uniform changes to the underlying statistical characteristics of the signal to weaken the periodic cyclic characteristics of the signal. It innovatively unifies "increasing speed" and "increasing concealment." In physical layer security applications, QNSC stream encryption technology uses photon fluctuations to achieve random encryption of signal levels. This invention breaks this limitation, applying the mechanism to the correlation domain of spread spectrum signals. It uses noise-induced correlation fluctuations to achieve random encryption of correlation data. In threat environments based on cyclic characteristic attacks, the combination of spread spectrum and stream encryption mechanisms makes the confidentiality of the spread spectrum code unnecessary. The source of security for the communication link shifts to key distribution in the secure channel, which cannot be obtained through blind estimation, resulting in extremely high security. Attached Figure Description

[0040] Figure 1 This is a flowchart of a secure spread spectrum communication method based on stream encryption provided in an embodiment of the present invention.

[0041] Figure 2 This is a block diagram of a secure spread spectrum communication system based on stream encryption provided in an embodiment of the present invention.

[0042] Figure 3 This is a result diagram of the bitrate feature suppression provided in the embodiments of the present invention.

[0043] Figure 4 This is a result diagram of periodic feature suppression provided in an embodiment of the present invention.

[0044] Figure 5 This is a distribution diagram of the correlation unspread values ​​of the 16 sequences provided in the embodiments of the present invention.

[0045] Figure 2 The module consists of: 1. Pre-encryption module; 2. Constellation shaping module; 3. Higher-order mapping module; 4. Spread spectrum modulation module; 5. Randomization module; and 6. Editing module. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0047] like Figure 1 As shown, the secure spread spectrum communication method based on stream encryption provided by this embodiment of the invention includes the following steps:

[0048] S101, perform XOR encryption on the input binary data to obtain an encrypted binary sequence;

[0049] S102, Perform probability amplitude shaping on the encrypted binary sequence to generate a constellation symbol sequence with a preset probability distribution;

[0050] S103, perform high-order constellation mapping processing on the constellation symbol sequence to generate high-order modulation symbols and output two data paths, wherein the first data path is used to generate spread spectrum sequence control information and the second data path is used for spread spectrum modulation input;

[0051] S104, Generate a corresponding spreading sequence according to the spreading sequence control information;

[0052] S105, Perform spread spectrum modulation processing according to the spread spectrum sequence and the higher-order modulation symbols;

[0053] S106 performs randomization processing on the spread spectrum modulation result to obtain a spread spectrum signal with suppressed features.

[0054] The probability amplitude shaping provided in this embodiment of the invention is achieved through a constant constant combination distribution matching method, and the sign probability distribution is determined based on the exponential function of the square of the constellation point amplitude.

[0055] The XOR encryption process provided in this embodiment of the invention generates a binary ciphertext sequence by performing an XOR operation bit by bit between the binary plaintext sequence and the binary key sequence.

[0056] The high-order constellation mapping processing provided in this embodiment of the invention forms high-order modulation symbols by appending an encryption base sequence to the tail of the binary symbols corresponding to constellation points.

[0057] The core of this invention lies in breaking through the traditional design concept of separating "security" and "transmission" in communication systems, and constructing a closed-loop collaborative working mechanism that integrates data encryption, probabilistic shaping, and spread spectrum modulation. Unlike the simple superposition or splicing in existing technologies, this application, through a unique signal flow path and control logic, establishes a deep causal relationship and performance gain between each step, thereby achieving simultaneous optimization of feature suppression and transmission efficiency at the physical layer.

[0058] First, this embodiment constructs a low-level fusion mechanism of "key diffusion" and "probabilistic shaping".

[0059] As described in step S101, the system performs XOR encryption on the input binary data. It is important to emphasize that this XOR encryption is not an isolated security measure; the output encrypted binary sequence will directly serve as the input source for Probabilistic Amplitude Shaping (PAS). In traditional designs, the encryption layer and the encoding layer are often independent. The encrypted data, due to its high randomness, often disrupts the specific distribution characteristics required for probability shaping, leading to the failure of the shaping gain. However, in this embodiment, step S102 uses a constant constant combination distribution matching method (CCDM) and determines the symbol probability distribution based on the exponential function of the squared amplitude of the constellation points. This means that when the encrypted sequence enters the shaper, it is not passively mapped but actively participates in the construction of the probability model. Each change in the encryption key dynamically fine-tunes the probability of constellation point occurrence through the XOR result of the binary sequence. This “encryption-guided shaping” design ensures that even under the same signal-to-noise ratio environment, the probability distribution of the symbols received by the eavesdropper is approximately uniform (high-entropy state) because the eavesdropper cannot recover the key, while the legitimate receiver can recover a non-uniform distribution with low entropy, thus obtaining an additional “probability domain” security margin at the physical layer in addition to the signal-to-noise ratio gain.

[0060] Secondly, this embodiment features a unique serial-parallel data splitting architecture based on "high-order mapping-spread spectrum control".

[0061] In step S103, the constellation symbol sequence after probability shaping is subjected to higher-order constellation mapping to generate higher-order modulation symbols. The key technological breakthrough in this process lies in its output method: simultaneously outputting two data streams with different functions.

[0062] The first data stream does not contain specific information to be transmitted; instead, it serves as "metadata" used to generate spread spectrum sequence control information. This means that changes in the spread spectrum sequence no longer depend on a fixed pseudo-random code, but are deeply bound to the encrypted and shaped signal characteristics.

[0063] - The second data path carries the core payload of encrypted information and enters the spread spectrum modulation input.

[0064] The essence of this division of labor lies in transforming the traditionally independent process of "spreading code selection" into a function of the "information signal." Step S104 generates the corresponding spreading sequence based on the spreading sequence control information, effectively realizing signal-dependent spreading. For legitimate receivers, possessing the key, they can accurately parse the first-path control information, thereby synchronously generating the correct spreading code for despreading. For illegitimate receivers, unable to extract the control information from the chaotic constellation symbols, they face not only demodulation difficulties but also ignorance of the spreading codebook, greatly enhancing the system's anti-interception capability.

[0065] Furthermore, this embodiment achieves a secondary obfuscation of "spread spectrum modulation" and "feature randomization".

[0066] In step S105, spread spectrum modulation is performed based on the spread spectrum sequence and higher-order modulation symbols. Although the signal is spread in the time-frequency domain, its statistical characteristics (such as cyclic spectrum features and higher-order moment features) may still be detected by a professional, non-cooperative receiver using a blind identification algorithm. Therefore, step S106 performs randomization processing on the spread spectrum modulation result to obtain a spread spectrum signal with suppressed features.

[0067] This randomization process is not a simple amplitude perturbation, but a feature elimination operation targeting the inherent periodic stationary characteristics of the spread spectrum signal. It complements the probabilistic amplitude shaping (S102) at the front end: the front-end PAS reduces the visual regularity of the signal on the constellation diagram by changing the occurrence probability of constellation points; the back-end randomization further eliminates the periodic statistical features introduced by the spreading code. This collaborative design of "suppressing geometric features at the front end and suppressing statistical features at the back end" results in the final output signal exhibiting statistical characteristics similar to Gaussian noise in the wireless channel, greatly increasing the difficulty of signal detection and parameter estimation.

[0068] This embodiment forms an organic technical whole through a complete technical chain: "XOR encryption provides an entropy source, probability shaping shapes the distribution, high-order mapping controls the flow, spread spectrum modulation spreads the spectrum, and randomization suppresses features." Among these, probability amplitude shaping is not only for improving transmission efficiency but also for building a security barrier in the probability domain; the generation of the spread spectrum sequence is no longer independent but controlled by the encrypted data stream; and the final randomization process protects against the security vulnerabilities of spread spectrum modulation.

[0069] This collaborative working mechanism cannot be inspired by simple combinations of "encryption + modulation" or "shaping + encoding" in existing technologies. Existing technologies often suffer from the inherent bias of "security and efficiency being mutually restrictive," assuming that enhanced security inevitably sacrifices bandwidth efficiency. However, this invention uses encrypted information as a control signal to dynamically adjust spreading and shaping parameters, enabling security and transmission functions to mutually enhance each other within the same physical layer process, achieving the technical effect of "security gain without a significant decrease in spectral efficiency." This holistic design scheme, which deeply integrates multiple technologies to form complementary functions and mutually reinforcing performance, far exceeds the scope that those skilled in the art can obtain through simple logical reasoning inspired by existing fragmented technologies.

[0070] Another objective of this invention is to provide a secure spread spectrum communication method based on stream encryption, comprising the following steps:

[0071] Obtain the control data output by the higher-order constellation mapping module;

[0072] Edit the spread spectrum sequence based on the control data;

[0073] Select the corresponding spreading sequence based on the higher-order modulation symbols;

[0074] Spread spectrum modulation is performed on the spread spectrum sequence and higher-order modulation symbols to generate a spread spectrum signal;

[0075] Randomization processing is performed on the spread spectrum signal to generate a random spread spectrum sequence.

[0076] The randomization process provided in this embodiment of the invention is achieved by performing random rotations on the spread spectrum sequence in the vector space.

[0077] An embodiment of the present invention provides a secure spread spectrum communication method based on stream encryption, comprising the following steps:

[0078] (1) The pre-encryption module is used to perform preliminary XOR encryption on binary data;

[0079] (2) The constellation shaping module receives the output data from the pre-encryption module and processes it to obtain a constellation format with a probability distribution; the constellation shaping module inputs the result to the higher-order mapping module, the purpose of which is to obtain a more dense higher-order format constellation result;

[0080] (3) The high-order mapping module transmits the constellation format to the editing module through the first output port, and transmits the constellation data processing results to the spread spectrum modulation module through the second output port;

[0081] (4) The editing module completes the editing of the spread spectrum sequence based on the input format data;

[0082] (5) The spread spectrum modulation module selects the corresponding spread spectrum sequence based on the output of the editing module and the input content, and inputs the result to the randomization module;

[0083] (6) The randomization module randomizes the input result and outputs the signal after the suppressed features are obtained, thus completing the initial processing of the entire signal.

[0084] The constellation shaping module provided in this embodiment of the invention performs probability amplitude shaping (PAS) using a constant constant distribution matched pair (CCDM). The probability distribution conforms to the following formula based on the set shaping coefficient v:

[0085]

[0086] In the formula, the output symbol conforms to x represents the amplitude value of the target constellation format point.

[0087] The XOR encryption module provided in this embodiment of the invention will convert binary plaintext into binary plaintext. Using binary keys XOR encryption to obtain binary ciphertext Its satisfying relation is: . It represents the XOR relationship between binary data.

[0088] The high-order mapping module provided in this embodiment of the invention directly adds an encryption base to the end of the binary format of the corresponding constellation point: , This indicates that binary modules are directly connected.

[0089] In this embodiment of the invention, a binary signal is input to a pre-encryption module 1, and the input terminal of a constellation shaping module 2 is connected to the output terminal of the pre-encryption module 1; the input terminal of a higher-order mapping module 3 is connected to the output terminal of the constellation shaping module 2; the first output terminal of the higher-order mapping 3 is connected to the input terminal of an editing module 6; the second output terminal of the higher-order mapping 3 is connected to the first input terminal of a spread spectrum modulation module 4; the input terminal of a randomization module 5 is connected to the output terminal of a spread spectrum modulation module; and the output terminal of an editing module 6 is connected to the second input terminal of a spread spectrum modulation module.

[0090] The constellation shaping module 2 provided in this embodiment of the invention uses a constant constant distribution matcher (CCDM) to perform probability amplitude shaping. The keys used by the pre-encryption module 1 and the higher-order mapping module 3 are transmitted through a private channel and shared with the receiving end. The randomization module 5 performs random rotation of vectors in the vector space. That is, the output of the editing module 6 is randomly rotated around the unedited sequence to complete the randomization. After that, the randomized sequence is fitted with a fixed number of chips of unequal length.

[0091] like Figure 2 As shown, an embodiment of the present invention provides a secure spread spectrum communication system based on stream encryption, comprising:

[0092] Pre-encryption module 1 is used to perform preliminary XOR encryption on binary data;

[0093] Constellation shaping module 2 is used to receive the output data from the pre-encryption module and process it to obtain a constellation format with a probability distribution; constellation shaping module 2 inputs the result to higher-order mapping module 3, the purpose of which is to obtain a denser higher-order format constellation result;

[0094] The high-order mapping module 3 is used to transmit the constellation format to the editing module 6 through the first output port, and to transmit the constellation data processing result to the spread spectrum modulation module 4 through the second output port.

[0095] The spread spectrum modulation module 4 is used to select the corresponding spread spectrum sequence based on the output result and input content of the editing module 6, and input the result to the randomization module;

[0096] Randomization module 5 is used to randomize the input result and output it to obtain the signal after suppressing the features, thus completing the initial processing of the entire signal.

[0097] Editing module 6 is used to edit the spread spectrum sequence based on the input format data.

[0098] Specific implementation of the present invention:

[0099] This embodiment uses a specific process as an example.

[0100] Step 1: The binary data signal is processed by the pre-encryption module. In this example, PRBS15 is used as the original signal stream to be transmitted, and the signal stream is XOR encrypted according to the key.

[0101] Step 2: The pre-encryption module outputs ciphertext stream data as the input signal for the constellation shaping module, which then performs constellation mapping on the ciphertext stream data.

[0102] Step 3: The higher-order mapping module densifies the constellation diagram output by the constellation shaping module into a higher-order form by adding an encryption base to the end of the binary constellation point data. In this example, a 2-bit encryption base is used to output a 256-QAM higher-order constellation diagram.

[0103] Step 4: The editing module uses the constellation diagram format data output by the higher-order mapping module ( The correlation of the spreading code is edited, and 16 correlation sequences with equal spacing from the original spreading code are output.

[0104] Step 5: The randomization module outputs the 16 result sequences from the editing module corresponding to different constellation points, and outputs the randomized formed sequence.

[0105] I. In the constellation shaping module, probability amplitude shaping is performed using CCDM. In this example, the amplitude is set to {1, 3}, and the positive and negative signs can be generated randomly. The shaping probability is set according to the shaping coefficient, and the relationship between the two is as follows. The final output is a 16-QAM constellation symbol with a value of { }

[0106]

[0107] II. In the randomization module, the correlation values ​​between the 16 edited sequences and the original spreading code are discretely and uniformly distributed in the interval [-1, +1]. In the vector space, a new sequence is obtained without changing the correlation result by vector rotation.

[0108] Mathematically, this is achieved through vector decomposition, randomizing the components orthogonal to the original chaotic sequence. .

[0109]

[0110] The component that represents the vector after vector decomposition is parallel to the direction of the vector represented by the original chaotic sequence. Then it represents the component whose direction is perpendicular to the vector represented by the original chaotic sequence after vector decomposition.

[0111] After the new sequence is fitted into a curve, the curve is approximated and fitted using rectangular chips of different lengths. The fitted rectangular signal completes the processing of this invention.

[0112] Example: The spreading gain is set to 127, and the original chaotic sequence is generated using the standard normal distribution function (randn). Without loss of generality, this example uses a 2-bit encryption basis to illustrate the specific implementation details. In the Probability Amplitude Shaping (PAS) stage, the constant composition distribution matched unit (CCDM) shaping coefficient v is set to 0.4, and the amplitude... For simplicity of demonstration, the positive and negative signs are generated randomly instead of using FEC encoding. A complete constellation symbol consists of an amplitude term and a positive / negative sign term.

[0113] By superposition The encryption base generates a denser 256-QAM constellation symbol. Sixteen edited sequences are mapped to different constellation point coordinates and randomly rotated to suppress periodicity. Then, chips of random length are used for shaping. After fitting, the sequences are reconstructed using rectangular chips of different lengths. In this example, the average chip rate is set to 1 Hz, with a dynamic range of 0.6–1.5 Hz. To suppress inter-symbol interference (ISI), a roll-off factor is used in the simulation. The root raised cosine (RRC) filter shapes and filters rectangular pulses and modulates them onto a 10Hz carrier frequency.

[0114] from Figure 3 As can be seen, the left figure, representing the traditional method, has peak features with 1Hz intervals, while the right figure, representing the present invention, does not have these equally spaced peak features.

[0115] from Figure 4 It can be seen that the plot representing the traditional method has peak features with equal intervals of spread spectrum gain 127, while the right-hand plot representing the present invention is very messy and cannot extract obvious equal-interval features.

[0116] Figure 5 As can be seen, the distribution of correlation unspread values ​​for the 16 sequences is shown in the diagram.

[0117] Example 1

[0118] In a basic communication scenario, the transmitting end first acquires the input binary data sequence and performs a bitwise XOR operation using the binary key sequence to form an encrypted sequence. Subsequently, the encrypted sequence undergoes probability amplitude shaping, and a constellation symbol sequence with a specific probability distribution is generated using a constant constant combination distribution matching method. This probability distribution is determined based on the squared exponential function of the constellation symbol amplitude, and its probability is calculated using an exponential function. The shaped symbol sequence is input to a higher-order mapping module, where an encrypted base sequence is appended to the end of the symbol's binary representation to form a higher-order modulation symbol. This higher-order modulation symbol is output to the spread spectrum modulation module and simultaneously generates information for controlling the spread spectrum sequence. The spread spectrum sequence is then generated based on the control information and subjected to spread spectrum modulation processing with the higher-order modulation symbol. Finally, a vector space random rotation process is performed on the spread spectrum signal, causing the spread spectrum signal to exhibit randomized spatial distribution characteristics, thereby obtaining a communication signal with suppressed features.

[0119] Example 2

[0120] In a high-security communication scenario, after XOR encryption of the input data, probability amplitude shaping is used to make the probability of constellation symbols appear in a non-uniform distribution. This probability distribution is determined by an exponential function, with symbols with smaller amplitudes appearing more frequently than those with larger amplitudes. The constellation sequence generated in this way approximates a Gaussian distribution in statistical characteristics, improving signal power utilization efficiency. Subsequently, higher-order constellation mapping is performed on the shaped symbols, expanding the symbol dimension by adding an encrypted base sequence. The mapped symbols are used to generate both spread spectrum sequence control information and spread spectrum modulation input data. The spread spectrum sequence is reconstructed by an editing module, so that different data segments correspond to different spread spectrum sequences. The spread spectrum modulation module then maps different higher-order symbol information to spread spectrum sequence signals with varying correlations. A randomization module performs spatial random rotation on the signal and reconstructs the rotated sequence using a fixed number of chips to reduce the probability of signal features being identified.

[0121] Example 3

[0122] In a low probability of intercept (POC) communication scenario, a constellation symbol sequence of ±1 and ±3 is generated through probability amplitude shaping, and its occurrence probability is determined according to an exponential function. The shaped symbols enter a higher-order mapping module, where an encryption base sequence is appended to the end of the symbol's binary structure to form extended symbols. After the extended symbols are output, a portion is used to drive the spread spectrum sequence editing module to generate the corresponding spread spectrum sequence, and the other portion is used by the spread spectrum modulation module. The spread spectrum sequence editing module modifies the original sequence according to the symbol structure, ensuring that the spread spectrum sequence structure changes with the input symbols. Subsequently, the spread spectrum modulation module combines the higher-order symbols with the spread spectrum sequence for modulation. A randomization module processes the spread spectrum signal through random rotation of the vector space, making the signal's statistical characteristics more uniform, thereby reducing the likelihood of being detected by a detection system.

[0123] Example 4

[0124] In a complex electromagnetic environment communication scenario, the input data is XOR-encrypted by a pre-encryption module, providing initial encryption protection for the original information before it enters the modulation stage. Subsequently, a probability amplitude shaping module generates a constellation symbol sequence with a specified probability distribution. The shaped symbols are input to a higher-order mapping module, which generates higher-order modulation symbols by adding an encrypted basis sequence. The mapping module simultaneously outputs spreading sequence control information. An editing module generates the corresponding spreading sequence based on this control information, ensuring the spreading sequence changes with the data. The spreading modulation module performs spreading processing based on the generated spreading sequence and the higher-order modulation symbols. Finally, a randomization module performs spatial rotation processing on the spread spectrum signal, further dispersing the signal energy in space, thereby improving the communication's anti-interference capability.

[0125] Example 5

[0126] In a high-capacity communication system, the distribution of constellation symbols is optimized using probabilistic amplitude shaping techniques to reduce the average power of the higher-order modulation signal. The shaping process calculates the probability of occurrence of each constellation symbol using an exponential function and generates corresponding symbol sequences through distribution matching. Subsequently, a higher-order mapping module generates higher-order modulation symbols by appending an encryption base sequence to the binary representation of the symbols. These symbols simultaneously drive the spread spectrum sequence generation and spread spectrum modulation input. The spread spectrum sequence is reconstructed by an editing module to establish a correspondence between the spread spectrum sequence structure and the data content. The spread spectrum modulation module combines the symbols and the spread spectrum sequence to form a spread spectrum signal. A randomization module randomizes the signal through random rotation of the vector space and chip reconstruction, making the spread spectrum signal more uniform in statistical characteristics.

[0127] Example 6

[0128] In a broadband spread spectrum communication system, after generating an encrypted data sequence through XOR encryption, a constellation symbol sequence with an exponential probability distribution is constructed using a probability amplitude shaping module. The shaped symbols enter a higher-order mapping module, which expands the symbol dimension by adding an encrypted base sequence to form higher-order modulation symbols. The mapping module outputs two channels of information: one for the spread spectrum sequence editing module to generate the spread spectrum sequence, and the other for the spread spectrum modulation module. The spread spectrum modulation module combines the higher-order modulation symbols with the spread spectrum sequence to generate a spread spectrum signal. A randomization module processes the spread spectrum signal through random rotation of the vector space and reconstructs the random sequence using a fixed number of chips, so that the final signal exhibits random distribution characteristics in both the time and frequency domains, thereby improving the system's anti-interception and anti-interference capabilities.

[0129] As can be seen from the above implementation methods, a collaborative mechanism is formed among the various technical steps. Pre-encryption processing enhances data security, probability amplitude shaping optimizes signal statistical distribution, higher-order mapping increases symbol dimension, spread spectrum sequence editing and spread spectrum modulation realize spread spectrum communication functions, and randomization processing further reduces the saliency of signal features. The cooperation of multiple technical steps significantly improves the communication system's security, anti-interference capability, and stealth. The above implementation methods support the proposed technical solution and enable those skilled in the art to implement corresponding systems.

[0130] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0131] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A secure spread spectrum communication method based on stream encryption, characterized in that, Includes the following steps: Step 1: Perform XOR encryption on the input binary data to obtain an encrypted binary sequence; Step 2: Perform probability amplitude shaping on the encrypted binary sequence to generate a constellation symbol sequence with a preset probability distribution; Step 3: Perform high-order constellation mapping processing on the constellation symbol sequence to generate high-order modulation symbols and output two data paths, wherein the first data path is used to generate spread spectrum sequence control information and the second data path is used for spread spectrum modulation input; Step 4: Generate the corresponding spreading sequence based on the spreading sequence control information; Step 5: Perform spread spectrum modulation processing based on the spread spectrum sequence and the higher-order modulation symbols; Step 6: Randomize the spread spectrum modulation result to obtain a spread spectrum signal with suppressed features.

2. The secure spread spectrum communication method based on stream encryption according to claim 1, characterized in that: The probability amplitude shaping is achieved through a constant constant combination distribution matching method, and the sign probability distribution is determined based on the exponential function of the square of the constellation point amplitude.

3. The secure spread spectrum communication method based on stream encryption according to claim 1, characterized in that: The XOR encryption process generates a binary ciphertext sequence by performing a bitwise XOR operation between the binary plaintext sequence and the binary key sequence.

4. The secure spread spectrum communication method based on stream encryption according to claim 1, characterized in that: The higher-order constellation mapping process forms higher-order modulation symbols by appending an encryption base sequence to the tail of the binary symbols corresponding to constellation points.

5. A spread spectrum sequence editing and modulation cooperative security spread spectrum communication method for implementing the security spread spectrum communication method based on stream encryption according to any one of claims 1-4, characterized in that, This method, based on the secure spread spectrum communication method with stream encryption as described in claim 1, includes the following steps: Obtain the control data output by the higher-order constellation mapping module; Edit the spread spectrum sequence based on the control data; Select the corresponding spreading sequence based on the higher-order modulation symbols; Spread spectrum modulation is performed on the spread spectrum sequence and higher-order modulation symbols to generate a spread spectrum signal; Randomization processing is performed on the spread spectrum signal to generate a random spread spectrum sequence.

6. The spread spectrum sequence editing and modulation synergized secure spread spectrum communication method of claim 5, wherein: The randomization process is achieved by performing random rotations on the spread spectrum sequence in the vector space.

7. The secure spread spectrum communication method for coordinated spread spectrum sequence editing and modulation according to claim 5, characterized in that: After randomization, the random sequence is fitted using a fixed number of chips of varying lengths.

8. A secure spread spectrum communication system based on stream encryption for implementing the method of any one of claims 1 to 7, characterized in that, include: The pre-encryption module is used to perform XOR encryption on the input binary data; The constellation shaping module is used to perform probability amplitude shaping on the encrypted binary sequence; The higher-order mapping module is used to perform higher-order constellation mapping on the constellation shaping output and output two data streams. The editing module is used to generate spread spectrum sequences based on the output of the higher-order mapping module; The spread spectrum modulation module is used to perform spread spectrum modulation based on the spread spectrum sequence and higher-order modulation symbols; The randomization module is used to perform randomization processing on the spread spectrum modulation results and output the spread spectrum signal.

9. The secure spread spectrum communication system based on stream encryption according to claim 8, characterized in that: The constellation shaping module uses a constant constant combination distribution matching structure to achieve probability amplitude shaping.

10. The secure spread spectrum communication system based on stream encryption according to claim 8, characterized in that: The keys used by the pre-encryption module and the higher-order mapping module are shared between the sender and receiver via a private communication channel.

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