A data stream encryption method and device based on a fixed-point isomorphic chaotic system

Abstract

The application discloses a data stream encryption method and device based on a fixed-point heterogeneous chaotic system, and the method comprises the following steps: converting an image to be encrypted into a plaintext sequence represented in a binary format, and then acquiring a key negotiated by both communication parties; inputting the key into a pre-constructed fixed-point heterogeneous chaotic system to perform iterative operation, so as to obtain an initial chaotic sequence, wherein the fixed-point heterogeneous chaotic system comprises a PLCM mapping and an LTM mapping; performing threshold judgment on the initial chaotic sequence, so as to obtain a chaotic sequence represented in a binary format; performing exclusive OR processing on the plaintext sequence and the chaotic sequence, so as to obtain a ciphertext sequence corresponding to the image to be encrypted. The application can improve the sequence randomness weakening problem of the existing fixed-point chaotic system caused by the existing dynamic degradation effect under the condition of fixed-point precision, so that the encryption effect is better.

Description

Technical Field

[0001] This invention relates to the field of data encryption technology, specifically to a data stream encryption method and apparatus based on a fixed-point heterogeneous chaotic system. Background Technology

[0002] With the rapid development of multimedia and digital communication technologies, people have more and more information and communication between each other is becoming easier and easier. In order to protect data information from malicious theft, it is essential to encrypt data information.

[0003] Chaotic systems are nonlinear dynamical systems with inherent randomness, characterized by sensitivity to initial values, ergodicity, pseudo-randomness, and unpredictable trajectories. These characteristics give them unique advantages in cryptography, where they are often used as pseudo-random sequence generators. However, under the limited precision of computers, sequences obtained through chaotic systems still suffer from reduced randomness, insufficient resistance to interference, and insufficient resistance to interception. While existing floating-point chaotic systems can retain chaotic properties, they also increase computational load and hardware overhead. Furthermore, existing fixed-point chaotic systems, due to dynamic degradation effects, are prone to weakening sequence randomness. Summary of the Invention

[0004] This invention provides a data stream encryption method and apparatus based on a fixed-point heterogeneous chaotic system to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0005] Firstly, a data stream encryption method based on a fixed-point heterogeneous chaotic system is provided, including:

[0006] The image to be encrypted is converted into a plaintext sequence in binary format, and then the key obtained through negotiation between the communicating parties is acquired.

[0007] The key is input into a pre-constructed fixed-point heterogeneous chaotic system for iterative computation to obtain an initial chaotic sequence. The fixed-point heterogeneous chaotic system includes a PLACM mapping and an LTM mapping.

[0008] The initial chaotic sequence is subjected to threshold judgment to obtain a chaotic sequence represented in binary format;

[0009] The plaintext sequence and the chaotic sequence are XORed to obtain the ciphertext sequence corresponding to the image to be encrypted.

[0010] Furthermore, the key includes the number of iterations per round, an initial value, a first structural parameter associated with the PLCM mapping, and a second structural parameter associated with the LTM mapping.

[0011] Furthermore, the LTM mapping is obtained by coupling the Logistic mapping and the Tent mapping.

[0012] Furthermore, the key is input into a pre-constructed fixed-point heterogeneous chaotic system for iterative computation to obtain an initial chaotic sequence including:

[0013] Step 1: Determine the number of iteration rounds and denot it as N based on the length of the plaintext sequence and the number of iterations per round;

[0014] Step 2: Update the initial value using the PLCM mapping to obtain a first initial value and use it as the chaotic initial value required for the first round of iteration;

[0015] Step 3: In the i-th iteration, input the initial chaotic value required for the i-th iteration and the first structural parameter into the PLCM mapping to perform one operation to obtain the first initial chaotic value. Then, input the first initial chaotic value and the second structural parameter into the LTM mapping to perform internal iterative operation to obtain the i-th initial chaotic subsequence.

[0016] Step 4: Determine if i < N is true; if yes, assign i+1 to i, and use the first chaotic initial value as the chaotic initial value required for the i-th iteration, and return to step 3; if no, concatenate the N initial chaotic subsequences obtained by the iteration to obtain the initial chaotic sequence.

[0017] Further, determining the number of iteration rounds based on the length of the plaintext sequence and the number of iterations per round includes:

[0018] The length of the plaintext sequence is divided by the number of iterations in each round to obtain the quotient and the remainder.

[0019] When the remainder is zero, the quotient is used as the iteration round number; or, when the remainder is non-zero, the quotient is incremented by 1 as the iteration round number.

[0020] Furthermore, updating the initial value using the PLCM mapping to obtain the first initial value includes:

[0021] The initial value and the first structural parameter are input into the PLCM mapping for 20 iterations, and then the single value generated in the 20th iteration is used as the first initial value.

[0022] Furthermore, when performing each operation, the PLCM mapping converts the operation result into fixed-point 32-bit data and then rounds it down before outputting it.

[0023] Secondly, a data stream encryption device based on a fixed-point heterogeneous chaotic system is provided, comprising:

[0024] The acquisition module is used to convert the image to be encrypted into a plaintext sequence represented in binary format, and then acquire the key obtained through negotiation between the two communicating parties;

[0025] An iterative computation module is used to input the key into a pre-constructed fixed-point heterogeneous chaotic system for iterative computation to obtain an initial chaotic sequence. The fixed-point heterogeneous chaotic system includes a PLACM mapping and an LTM mapping.

[0026] The threshold judgment module is used to perform threshold judgment on the initial chaotic sequence to obtain a chaotic sequence represented in binary format;

[0027] The XOR processing module is used to perform XOR processing on the plaintext sequence and the chaotic sequence to obtain the ciphertext sequence corresponding to the image to be encrypted.

[0028] Thirdly, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the data stream encryption method based on a fixed-point heterogeneous chaotic system as described in the first aspect.

[0029] Fourthly, a computer-readable storage medium is provided, on which a computer program is stored, wherein when the computer program is executed by a processor, it implements the data stream encryption method based on a fixed-point heterogeneous chaotic system as described in the first aspect.

[0030] The present invention has at least the following beneficial effects: by proposing a fixed-point heterogeneous chaotic system composed of PLCM mapping and LTM mapping coupled with Tent mapping and Logistic mapping, and combining the key negotiated by the two communicating parties to perform encryption operation on the image to be encrypted, the invention utilizes a multi-chaotic random scrambling scheme to improve the problem of reduced sequence randomness caused by the dynamic degradation effect of the existing fixed-point chaotic system under the condition of fixed-point accuracy, thus making the encryption effect better. Attached Figure Description

[0031] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0032] Figure 1 This is a flowchart illustrating a data stream encryption method based on a fixed-point heterogeneous chaotic system according to an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the composition of a data stream encryption device based on a fixed-point heterogeneous chaotic system in an embodiment of the present invention;

[0034] Figure 3This is a schematic diagram of the hardware structure of the computer device in an embodiment of this disclosure. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] It should be noted that although functional modules are divided in the system diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the system or the order in the flowchart. The terms "first," "second," "third," "fourth," etc., used in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed and are inherent to these processes, methods, products, or apparatuses.

[0037] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating a data stream encryption method based on a fixed-point heterogeneous chaotic system provided by an embodiment of the present invention. The method includes the following:

[0038] Step S110: Convert the image to be encrypted into a plaintext sequence represented in binary format, and then obtain the key negotiated by both communicating parties;

[0039] Step S120: Input the key into a pre-constructed fixed-point heterogeneous chaotic system for iterative computation to obtain an initial chaotic sequence;

[0040] Step S130: Perform threshold judgment on the initial chaotic sequence to obtain a chaotic sequence represented in binary format;

[0041] Step S140: Perform an XOR operation between the plaintext sequence and the chaotic sequence to obtain the ciphertext sequence corresponding to the image to be encrypted.

[0042] In step S110 above, the image to be encrypted is actually an 8-bit grayscale image with a size of 512×512, and the value range of each pixel is [0,255]. After converting the image to be encrypted into a plaintext sequence, the length of the plaintext sequence should be 512×512×8.

[0043] In this embodiment of the invention, a fixed-point heterogeneous chaotic system is constructed first according to the user's encryption requirements. The fixed-point heterogeneous chaotic system is actually a chaotic pseudo-random sequence generator composed of PLCM mapping and LTM mapping. The LTM (The coupled Logistic-Tent) mapping is a one-dimensional chaotic mapping obtained by coupling the Tent mapping and the Logistic mapping. PLCM stands for Piecewise Linear Chaotic Map.

[0044] More specifically, in this embodiment of the invention, the expression for the PLCM mapping is defined as follows:

[0045]

[0046] In the formula, y n+1 y is the computational result generated by the PLCM mapping during the (n+1)th iteration. n The output of the PLCM mapping during the nth iteration is p, which is the first structural parameter associated with the PLCM mapping, and the value of the first structural parameter p should fall within the interval (0, 0.5).

[0047] More specifically, in this embodiment of the invention, the expression for the LTM mapping is defined as follows:

[0048]

[0049] In the formula, x n+1 x is the output of the LTM mapping during the (n+1)th iteration. n The output of the LTM mapping during the nth iteration is μ, which is the second structural parameter associated with the LTM mapping, and the value of the second structural parameter μ should fall within the interval (0,4].

[0050] It should be noted that, since the range of values ​​for the second structural parameter μ used in the LTM mapping is greater than the range of values ​​for the structural parameter used in a single Tent mapping, and also greater than the range of values ​​for the structural parameter used in a single Logistic mapping, the LTM mapping can improve the disadvantage that the sequences obtained by the Tent mapping or Logistic mapping at a certain structural parameter do not have uniform distribution characteristics.

[0051] In step S110 above, the key actually carries an initial value y0 jointly determined by the two communicating parties, the number of iterations per round M, the first structural parameter p, and the second structural parameter μ, wherein the number of iterations per round M can preferably be set to M = 1024.

[0052] In this embodiment of the invention, the specific implementation process of step S120 includes the following:

[0053] Step S121: Based on the number of iterations M carried in the key and the length of the plaintext sequence, determine the actual number of iterations required to be executed inside the fixed-point heterogeneous chaotic system and record it as N;

[0054] Step S122: In order to prevent the transient effects of chaos, the initial value y0 carried in the key is updated through the PLCM mapping to obtain the first initial value;

[0055] Step S123: Define the first initial value as the chaotic initial value that the fixed-point heterogeneous chaotic system needs to apply when performing the first round of iteration;

[0056] Step S124: When the fixed-point heterogeneous chaotic system performs the i-th iteration, the first structural parameter p carried in the key and the initial chaotic value required for the i-th iteration are substituted into the expression of the PLCM mapping for one operation to obtain the first initial chaotic value.

[0057] Step S125: Substitute the second structural parameter μ carried in the key and the first chaotic initial value obtained by solving in step S124 into the expression of the LTM mapping to perform internal iterative calculation, and the i-th initial chaotic subsequence can be obtained.

[0058] Step S126: Determine whether i is less than the number of iterations N; if yes, proceed to step S127; if no, proceed to step S128.

[0059] Step S127: Assign i+1 to i, and define the first chaotic initial value obtained by solving through step S124 as the chaotic initial value that the fixed-point heterogeneous chaotic system needs to apply when performing the i-th iteration, and then return to execute step S124.

[0060] Step S128: After N rounds of iteration, N initial chaotic subsequences can be obtained. The N initial chaotic subsequences are spliced ​​together in the order of acquisition time from first to last to obtain the initial chaotic sequence.

[0061] It should be noted that step S124 above is executed starting from i=1.

[0062] In step S121 above, the length of the plaintext sequence (i.e., 512×512×8) is divided by the number of iterations M to obtain the quotient Q and the remainder R; when the remainder R is identified as zero, the number of iterations N is directly determined to be Q; or, when the remainder R is identified as non-zero, the number of iterations N is determined to be Q+1.

[0063] In step S122 above, the first structural parameter p and the initial value y0 are first substituted into the expression of the PLCM mapping and 20 iterations are performed to obtain an array of length 21, {y0, y1, y2, ..., y0}. k ,...,y 20}, where y k The output of the PLCM mapping during the k-th (1≤k≤20) iteration is given; secondly, the first 20 outputs in this array are discarded, and only the last output y in the array is given. 20 The first initial value is used as the first value; it should be noted that the first structural parameter p should remain unchanged when the PLCM mapping is performed in each iteration.

[0064] In this embodiment of the invention, the required fixed-point precision is preferentially set to 32 bits. In steps S122 and S124 above, when the PLCM mapping performs each iteration operation, the operation result needs to be fixed-point converted according to the fixed-point precision to obtain fixed-point 32-bit data. Then, the fixed-point 32-bit data is rounded down to obtain the final iteration output result. It should be noted that the initial value y0 carried in the key is also fixed-point 32-bit data.

[0065] The above operation process is illustrated by the following example: Assume that the PLCM mapping outputs y after the 10th iteration. 10 Set the output result as y 10 Substituting the first structural parameter p into the expression for the PLCM mapping, the result can be solved as y. 11 At this point, the result y of the calculation needs to be... 11 y is obtained by performing point-to-point processing. ′ =y 11 / 2 32 Then, the fixed-point 32-bit data y ′ Perform a floor operation to obtain the output result of the PLCM mapping after the 11th iteration, and assign it to y. 11 .

[0066] When the iteration number N is Q, the specific implementation process of step S125 is as follows: In any iteration, the second structural parameter μ and the first chaotic initial value obtained in step S124 when executing the current iteration are substituted into the expression of the LTM mapping for M-1 iterations to obtain an array of length M, and the array is output as the initial chaotic subsequence generated in the current iteration; it should be noted that the second structural parameter μ should remain unchanged when the LTM mapping is executed in each iteration.

[0067] The i-th iteration process is illustrated by the following example: Since the first chaotic initial value obtained by step S124 in the i-th iteration is y 20+i The second structural parameter μ and the first chaotic initial value y are used to... 20+i Substituting the values ​​into the LTM mapping expression and performing M-1 iterations yields an array of length M. This array represents the output of the k-th (1≤k≤M-1) iteration within the LTM mapping in the i-th iteration, and is output as the initial chaotic subsequence generated in the i-th iteration (denoted as the i-th initial chaotic subsequence).

[0068] When the iteration number N is Q+1, the specific implementation process of step S125 is as follows: For any iteration in the previous N-1 iterations, the second structural parameter μ and the first chaotic initial value obtained in step S124 during the current iteration are substituted into the expression of the LTM mapping for M-1 iterations to obtain an array of length M, and the array is output as the initial chaotic subsequence generated in the current iteration; in the last iteration, the second structural parameter μ and the first chaotic initial value obtained in step S124 during the last iteration are substituted into the expression of the LTM mapping for R-1 iterations to obtain an array of length R, and the array is output as the initial chaotic subsequence generated in the last iteration; it should be noted that the second structural parameter μ should remain unchanged when the LTM mapping is executed for each iteration.

[0069] The final iteration process described above is illustrated by the following example: Since the first chaotic initial value obtained in step S124 during the final iteration is y 20+N The second structural parameter μ and the first chaotic initial value y are used to... 20+N Substituting the values ​​into the LTM mapping expression and performing R-1 iterations yields an array of length R. This array represents the output of the k-th (1≤k≤R-1) iteration within the LTM mapping during the N-th iteration, and is output as the initial chaotic subsequence generated in the last iteration (denoted as the N-th initial chaotic subsequence).

[0070] In step S128 above, when the number of iterations N is Q, the Q initial chaotic subsequences of length M obtained after N iterations can be sorted in ascending order of the number of iterations to obtain an initial chaotic sequence of length Q×M. That is, the length of the initial chaotic sequence is actually the same as the length of the plaintext sequence.

[0071] In step S128 above, when the number of iterations N is Q+1, the Q initial chaotic subsequences of length M obtained after the previous N-1 iterations and the single initial chaotic subsequence of length R obtained after the last iteration can be sorted in ascending order of iteration number to obtain an initial chaotic sequence of length Q×M+R. That is, the length of the initial chaotic sequence is actually the same as the length of the plaintext sequence.

[0072] In step S130 above, each value contained in the initial chaotic sequence is judged one by one; if the current value is greater than 0.5, the current value is directly updated to 1; if the current value is less than or equal to 0.5, the current value is directly updated to 0, thereby converting the initial chaotic sequence into a chaotic sequence represented in binary format.

[0073] In step S140 above, each value contained in the chaotic sequence is XORed with a single value contained in the plaintext sequence to obtain the ciphertext sequence after the complete encryption operation is performed on the image to be encrypted; that is, the first value contained in the ciphertext sequence is actually the result of the XOR operation between the first value contained in the chaotic sequence and the first value contained in the plaintext sequence, the second value contained in the ciphertext sequence is actually the result of the XOR operation between the second value contained in the chaotic sequence and the second value contained in the plaintext sequence, and so on.

[0074] It should be noted that, in another exemplary embodiment, when the iteration number N is Q, the plaintext sequence can be preferentially divided into Q plaintext subsequences on an average basis. After executing the above step S125, the i-th initial chaotic subsequence is subjected to threshold judgment to obtain the i-th chaotic subsequence represented in binary format. Then, the i-th chaotic subsequence is XORed with the i-th plaintext subsequence among the Q plaintext subsequences to obtain the i-th ciphertext subsequence. At this time, the above step S126 is continued. When it is determined that i is equal to the iteration number N, the N ciphertext subsequences obtained after N iterations are directly concatenated in the order of acquisition time from first to last to obtain the ciphertext sequence after performing a complete encryption operation on the image to be encrypted.

[0075] It should be noted that, in another exemplary embodiment, when the iteration number N is Q+1, the plaintext sequence can be divided into Q+1 plaintext subsequences with the iteration number M as the step size (where 1 represents that the length of the last plaintext subsequence is less than M). After executing the above step S125, the i-th initial chaotic subsequence is subjected to threshold judgment to obtain the i-th chaotic subsequence represented in binary format. Then, the i-th chaotic subsequence is XORed with the i-th plaintext subsequence in the Q+1 plaintext subsequences to obtain the i-th ciphertext subsequence. At this time, the above step S126 is continued. When it is determined that i is equal to the iteration number N, the N ciphertext subsequences obtained after N iterations are directly concatenated in the order of acquisition time from first to last to obtain the ciphertext sequence after the complete encryption operation on the image to be encrypted.

[0076] It should be noted that the fixed-point heterogeneous chaotic system provided in the embodiments of the present invention can also be applied to encrypt data streams such as text data, voice data, and video data. The encryption method for any type of data stream is similar to the encryption method for image data provided in the embodiments of the present invention, and will not be described in detail here.

[0077] In this embodiment of the invention, a fixed-point heterogeneous chaotic system composed of PLCM mapping and LTM mapping coupled with Tent mapping and Logistic mapping is proposed. The encryption operation is performed on the image to be encrypted by combining the key negotiated by the two communicating parties. The multi-chaotic random scrambling scheme can improve the problem of reduced sequence randomness caused by the dynamic degradation effect of the existing fixed-point chaotic system under the condition of fixed-point accuracy, so as to make the encryption effect better.

[0078] Please refer to Figure 2 , Figure 2This is a schematic diagram of a data stream encryption device based on a fixed-point heterogeneous chaotic system provided in an embodiment of the present invention. The device includes the following components:

[0079] The acquisition module 210 is used to convert the image to be encrypted into a plaintext sequence and acquire the key obtained through fair negotiation between the two communicating parties; wherein the plaintext sequence is represented in binary format.

[0080] The iterative operation module 220 is used to input the key into a fixed-point heterogeneous chaotic system composed of LTM mapping and PLACM mapping to perform iterative operations, thereby obtaining an initial chaotic sequence.

[0081] Threshold judgment module 230 is used to perform threshold judgment on the initial chaotic sequence to obtain a chaotic sequence, wherein the chaotic sequence is represented in binary format;

[0082] The XOR processing module 240 is used to perform XOR processing on the chaotic sequence and the plaintext sequence to obtain the ciphertext sequence corresponding to the image to be encrypted.

[0083] The content of the above method embodiments is applicable to the device embodiments. The functions implemented by the device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are the same as those of the above method embodiments, so they will not be repeated here.

[0084] Furthermore, embodiments of the present invention also provide a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the data stream encryption method based on a fixed-point heterogeneous chaotic system described in the above embodiments. The computer-readable storage medium includes, but is not limited to, any type of disk (including floppy disks, hard disks, optical disks, CD-ROMs, and magneto-optical disks), ROM (Read-Only Memory), RAM (Random Access Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory, magnetic cards, or optical cards. In other words, the storage device includes any medium on which a device (e.g., a computer, mobile phone, etc.) stores or transmits information in a readable form, and can be a read-only memory, a disk, or an optical disk, etc.

[0085] also, Figure 3This is a schematic diagram of the hardware structure of a computer device provided in an embodiment of the present invention. The computer device includes components such as a processor 320, a memory 330, an input unit 340, and a display unit 350. Those skilled in the art will understand that... Figure 3 The illustrated device structure is not intended to limit all devices and may include more or fewer components than shown, or combine certain components. The memory 330 can be used to store the computer program 310 and various functional modules. The processor 320 runs the computer program 310 stored in the memory 330, thereby performing various functional applications and data processing of the device. The memory can be internal memory or external memory, or include both internal and external memory. Internal memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory, or random access memory. External memory may include hard disks, floppy disks, ZIP disks, USB flash drives, magnetic tapes, etc. The memory 330 disclosed in the embodiments of this invention includes, but is not limited to, these types of memory. The memory 330 disclosed in the embodiments of this invention is only an example and not a limitation.

[0086] Input unit 340 is used to receive signal input and user-input keywords. Input unit 340 may include a touch panel and other input devices. The touch panel can collect user touch operations on or near it (such as operations performed by the user using a finger, stylus, or any suitable object or accessory on or near the touch panel) and drive the corresponding connection device according to a pre-set program; other input devices may include, but are not limited to, one or more of physical keyboards, function keys (such as play control buttons, power buttons, etc.), trackballs, mice, joysticks, etc. Display unit 350 can be used to display user-input information or information provided to the user, as well as various menus of the terminal device. Display unit 350 may be in the form of a liquid crystal display, organic light-emitting diode, etc. Processor 320 is the control center of the terminal device, connecting various parts of the entire device through various interfaces and lines, performing various functions and processing data by running or executing software programs and / or modules stored in memory 320, and calling data stored in memory.

[0087] As one embodiment, the computer device includes a processor 320, a memory 330, and a computer program 310, wherein the computer program 310 is stored in the memory 330 and configured to be executed by the processor 320, and the computer program 310 is configured to perform the data stream encryption method based on a fixed-point heterogeneous chaotic system in the above embodiment.

[0088] Although the description of this application has been quite detailed and particularly focused on several of the described embodiments, it is not intended to limit itself to any of these details or embodiments or any particular embodiment. Rather, it should be considered as effectively covering the intended scope of this application by referring to the appended claims and taking into account the prior art, which provides for a broad possible interpretation of these claims. Furthermore, the foregoing description of this application with respect to embodiments foreseeable by the inventors is intended to provide a useful description, and non-substantial modifications to this application that have not yet been foreseen may still represent equivalent modifications.

Claims

1. A data stream encryption method based on a fixed-point heterogeneous chaotic system, characterized in that, include: The image to be encrypted is converted into a plaintext sequence in binary format, and then the key obtained through negotiation between the communicating parties is acquired. The key is input into a pre-constructed fixed-point heterogeneous chaotic system for iterative computation to obtain an initial chaotic sequence. The fixed-point heterogeneous chaotic system includes a PLACM mapping and an LTM mapping. The LTM mapping is obtained by coupling a Logistic mapping and a Tent mapping. The initial chaotic sequence is subjected to threshold judgment to obtain a chaotic sequence represented in binary format; The plaintext sequence and the chaotic sequence are XORed to obtain the ciphertext sequence corresponding to the image to be encrypted. The key includes the number of iterations per round, an initial value, a first structural parameter associated with the PLCM mapping, and a second structural parameter associated with the LTM mapping. The key is input into a pre-constructed fixed-point heterogeneous chaotic system for iterative computation to obtain an initial chaotic sequence, including: Step 1: Determine the number of iteration rounds and denot it as N based on the length of the plaintext sequence and the number of iterations per round; Step 2: Update the initial value using the PLCM mapping to obtain a first initial value and use it as the chaotic initial value required for the first round of iteration; Step 3: In the i-th iteration, input the initial chaotic value required for the i-th iteration and the first structural parameter into the PLCM mapping to perform one operation to obtain the first initial chaotic value. Then, input the first initial chaotic value and the second structural parameter into the LTM mapping to perform internal iterative operation to obtain the i-th initial chaotic subsequence. Step 4: Determine if i < N is true; if yes, assign i+1 to i, and use the first chaotic initial value as the chaotic initial value required for the i-th iteration, and return to step 3; if no, concatenate the N initial chaotic subsequences obtained by the iteration to obtain the initial chaotic sequence.

2. The data stream encryption method based on a fixed-point heterogeneous chaotic system according to claim 1, characterized in that, Determining the number of iteration rounds based on the length of the plaintext sequence and the number of iterations per round includes: The length of the plaintext sequence is divided by the number of iterations in each round to obtain the quotient and the remainder. When the remainder is zero, the quotient is used as the iteration round number; or, when the remainder is non-zero, the quotient is incremented by 1 as the iteration round number.

3. The data stream encryption method based on a fixed-point heterogeneous chaotic system according to claim 1, characterized in that, Updating the initial value using the PLCM mapping to obtain the first initial value includes: The initial value and the first structural parameter are input into the PLCM mapping for 20 iterations, and then the single value generated in the 20th iteration is used as the first initial value.

4. The data stream encryption method based on a fixed-point heterogeneous chaotic system according to claim 1 or 3, characterized in that, When performing each operation, the PLCM mapping converts the result into fixed-point 32-bit data and then rounds it down before outputting it.

5. A data stream encryption device based on a fixed-point heterogeneous chaotic system, characterized in that, include: The acquisition module is used to convert the image to be encrypted into a plaintext sequence represented in binary format, and then acquire the key obtained through negotiation between the two communicating parties; An iterative computation module is used to input the key into a pre-constructed fixed-point heterogeneous chaotic system for iterative computation to obtain an initial chaotic sequence. The fixed-point heterogeneous chaotic system includes a PLACM mapping and an LTM mapping. The LTM mapping is obtained by coupling a Logistic mapping and a Tent mapping. The threshold judgment module is used to perform threshold judgment on the initial chaotic sequence to obtain a chaotic sequence represented in binary format; An XOR processing module is used to perform an XOR operation on the plaintext sequence and the chaotic sequence to obtain the ciphertext sequence corresponding to the image to be encrypted. The key includes the number of iterations per round, an initial value, a first structural parameter associated with the PLCM mapping, and a second structural parameter associated with the LTM mapping. The key is input into a pre-constructed fixed-point heterogeneous chaotic system for iterative computation to obtain an initial chaotic sequence, including: Step 1: Determine the number of iteration rounds and denot it as N based on the length of the plaintext sequence and the number of iterations per round; Step 2: Update the initial value using the PLCM mapping to obtain a first initial value and use it as the chaotic initial value required for the first round of iteration; Step 3: In the i-th iteration, input the initial chaotic value required for the i-th iteration and the first structural parameter into the PLCM mapping to perform one operation to obtain the first initial chaotic value. Then, input the first initial chaotic value and the second structural parameter into the LTM mapping to perform internal iterative operation to obtain the i-th initial chaotic subsequence. Step 4: Determine if i < N is true; if yes, assign i+1 to i, and use the first chaotic initial value as the chaotic initial value required for the i-th iteration, and return to step 3; if no, concatenate the N initial chaotic subsequences obtained by the iteration to obtain the initial chaotic sequence.

6. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, The processor executes the computer program to implement the data stream encryption method based on a fixed-point heterogeneous chaotic system as described in any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the data stream encryption method based on a fixed-point heterogeneous chaotic system as described in any one of claims 1 to 4.

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