Image hybrid coding and encryption method based on four-dimensional hyper-chaotic system

Abstract

The invention relates to the technical field of image encryption, in particular to an image hybrid coding and encryption method based on a four-dimensional hyper-chaotic system. Comprising the steps that firstly, initial conditions and parameter values of a four-dimensional system, Arnod mapping and 2D-LSM are obtained through matrix and nonlinear function operation and visualization according to a specific algorithm in combination with basic data or preset constants such as an image size and a pixel mean value, and a foundation is laid for subsequent encryption; and then, the initial parameters are accessed to an iteration engine, iteration is carried out according to a chaotic dynamics rule, the iteration step number and the key stream generation process are displayed in real time, and an encrypted key stream is generated. Then, reading a plaintext image P, replacing related parameters with a formula, and disrupting a pixel sequence by using an Arnod scrambling algorithm to obtain a preliminary transformation image; according to the method, the four-dimensional hyper-chaotic system and various efficient image processing means can be deeply fused, high security and high reliability of image encryption are realized, various possible attacks can be effectively resisted, and confidentiality and integrity of image data are practically protected.

Description

Technical Field

[0001] The present invention relates to the technical field of image encryption, and in particular to a method for hybrid encoding and encryption of images based on a four-dimensional hyperchaotic system. Background Art

[0002] As digital technology develops at an alarming rate, images are becoming increasingly important in information dissemination and storage. In practical applications, image data often needs to be transmitted in different network environments or stored in various storage devices. However, in this process, image data is facing unprecedented security challenges.

[0003] The openness and complexity of cyberspace provide opportunities for criminals to illegally steal image information for illegal purposes through network monitoring, malware attacks, data interception, etc. At the same time, some people with ulterior motives may maliciously tamper with images, destroying the authenticity and integrity of the images, thus causing serious consequences. For example, in the medical field, tampering with medical images may lead to misdiagnosis; in the financial field, tampering with transaction voucher images may cause financial losses; in the military field, tampering with intelligence images may affect strategic decisions.

[0004] Traditional encryption methods have exposed many limitations when facing these complex and diverse security threats. Most of them are based on fixed encryption modes and algorithms, lack sufficient flexibility and adaptability, and are difficult to cope with increasingly complex attack methods. Moreover, with the rapid development of computer technology and the continuous improvement of computing power, the difficulty of cracking some traditional encryption methods has been greatly reduced, and they can no longer meet the stringent requirements of image data for security and privacy.

[0005] As a system with unique dynamic characteristics, chaotic system has brought new hope to the field of image encryption. Chaotic system is highly sensitive to initial conditions. Even if the initial value changes only slightly, the final result will be very different as the system evolves. At the same time, the sequence generated by chaotic system has strong randomness and unpredictability. These characteristics make it show great application potential in the field of cryptography. If the advantages of chaotic system can be organically integrated with a variety of advanced coding and transformation technologies, it is expected to build a more powerful and reliable image encryption system, providing strong protection for image data security. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a hybrid coding and encryption method for images based on a four-dimensional hyperchaotic system. The method can deeply integrate the four-dimensional hyperchaotic system with a variety of efficient image processing means, aiming to overcome the shortcomings of the prior art and achieve high security and high reliability of image encryption. It can effectively resist various possible attacks and effectively protect the confidentiality and integrity of image data.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A four-dimensional hyperchaotic system image hybrid coding and encryption method comprises the following steps:

[0009] Step 101: According to a preset algorithm, using basic information related to the image or preset constants, through complex mathematical operations, the initial conditions and parameter values ​​of the four-dimensional system, Arnold mapping, and two-dimensional logical self-mapping (2D-LSM) are accurately calculated to provide accurate starting settings for the subsequent encryption process. The complex mathematical operations include matrix operations and nonlinear function calculations to ensure that the obtained initial conditions and parameter values ​​are unique and stable to adapt to different image characteristics and encryption requirements;

[0010] Step 102: Import the initial conditions and parameter values ​​calculated in step 101 into the iteration module, perform iterative operations based on the built-in chaotic dynamics rules, and display the number of iteration steps and the dynamic generation of the key stream in real time during the iteration process to generate an encryption key stream with high randomness and high strength. The generation mechanism of the key stream ensures that it has sufficient complexity, making it difficult for the outside to crack or predict it through conventional means. The algorithm design of the iteration module should ensure the difference of the key stream in different encryption cycles on the previous day;

[0011] Step 103: Use the formula to replace the relevant parameters, drive the Arnold scrambling module to scramble the pixel positions of the plaintext image P, and the scrambling method is based on a specific scrambling algorithm to ensure that the original arrangement order of the pixels is effectively destroyed, and obtain a preliminary transformed image; then, introduce the key stream generated in the previous step and the 2D-LSM diffusion module, use the key stream to control the diffusion direction and intensity, combine the characteristics of 2D-LSM to perform a diffusion operation on the scrambled image, further blur the image features, and output the intermediate image P2. In this process, the parameter setting of the diffusion module should be closely coordinated with the key stream to achieve the best image blurring effect;

[0012] Step 104, with the help of another key stream generated by the four-dimensional hyperchaotic system, the intermediate image P2 is scrambled and diffused at the decimal level. The scrambling algorithm is designed based on the characteristics of decimal numbers. The diffusion operation uses the randomness of the key stream to completely disrupt the image data structure and successfully output the ciphertext image C. The design of the entire final encryption step ensures that the ciphertext image C has extremely high security, and it is difficult for an outsider to restore the original image through reverse engineering.

[0013] Furthermore, in step 101, it is necessary to first comprehensively and accurately obtain various basic information of the image to be encrypted, wherein the basic information includes the size of the image (denoted as S) and the pixel mean of each channel (denoted as M); combine it with the preset constant parameter (denoted as C), and then calculate it through the following algorithm f to generate the initial conditions of the four-dimensional hyperchaotic system. This process can be expressed by the formula:

[0014] IC=f(S,M,C)

[0015] Among them, IC represents the generated initial conditions, S represents the size information of the image, M represents the pixel mean, C represents the preset constant parameter, and f represents the algorithm function used to calculate the initial conditions.

[0016] Among them, the calculation algorithm of initial conditions and parameter values ​​should be adaptive and able to automatically adjust the operation parameters according to the resolution of the input image, control color mode and other characteristics to optimize the accuracy of the initial values ​​and improve the encryption effect.

[0017] The algorithm design here corresponds to the above-mentioned requirement of generating initial conditions by using basic image information and preset constants through complex mathematical operations (including matrix operations and nonlinear function calculations). The influence of image size, pixel mean and constant parameters on the initial conditions is comprehensively considered through linear combination and coefficient adjustment to ensure that the obtained initial conditions are unique and stable and can adapt to different image characteristics and encryption requirements.

[0018] Furthermore, in step 102, after the initial conditions are successfully generated, they are connected to a carefully constructed iteration engine; the iteration engine performs iteration operations strictly according to the dynamics rules of the four-dimensional hyperchaotic system; in each iteration process, according to the real-time output value of the chaotic system, a series of specific quantization and conversion operations are performed to generate a key stream fragment for the subsequent encryption link; if a formula is used to specifically describe this process, it is:

[0019] KS i =g(X i )

[0020] Among them, KS i represents the key stream fragment generated by the i-th iteration, S i represents the output value of the chaotic system in the i-th iteration, g represents the quantization and conversion function; X i is the state vector of the four-dimensional hyperchaotic system at the th iteration.

[0021] Among them, the iteration module in the key stream generation step here should be controllable, and be able to adjust low-voltage parameters such as the number of iteration steps and iteration speed according to encryption requirements to generate key streams of different lengths and complexities to meet diverse encryption scenarios.

[0022] Furthermore, in step 103, the plaintext image is firstly read and analyzed comprehensively and carefully, and converted into a matrix form that is convenient for subsequent processing; such conversion can make the image data easier to perform various mathematical operations and transformations in subsequent encryption operations. After the conversion is completed, the image is then preprocessed, such as normalization. Normalization can make the image pixel values ​​uniformly distributed within a specific range, eliminate the encryption interference that may be caused by the difference in pixel value ranges of different images, and provide a more standardized data basis for subsequent encoding transformations;

[0023] Subsequently, a variety of advanced coding techniques, such as Arnold transform and two-dimensional logical self-mapping, are used to perform comprehensive coding transformation on the preprocessed image. Taking Arnold transform as an example, its transformation formula is:

[0024]

[0025] Among them, (x, y) represents the coordinates of the original image pixel, (x new ,y new ) represents the coordinates of the transformed pixel, a and b are the transformation parameters, and N is the size of the image.

[0026] Among them, the Arnold scrambling module and the 2D-LSM diffusion module in the image transformation step here should be synergistic and be able to adjust the scrambling and diffusion strategies in real time according to the feedback of the key stream, so that the image always maintains a high degree of confusion during the transformation process and prevents the image features from being exposed prematurely.

[0027] Furthermore, in step 104, the key stream generated in step 102 and the image obtained in step 103 after multiple rounds of transformation are deeply fused and encrypted; the specific encryption method is to perform XOR operations, substitution operations and other operations on the transformed image pixels according to the value of the key stream at each coordinate position, and these operations can completely disrupt the image information and realize effective encryption of the image; the encryption process is expressed by the formula:

[0028]

[0029] Among them, C (x,y) represents the pixel value of the encrypted image at the (x, y) coordinate, T (x,y) Represents the pixel value of the transformed image at the (x,y) coordinate, Indicates XOR operation, KS (x,y) Indicates the key stream value at the corresponding coordinate;

[0030] After completing the above complete and rigorous steps, the final ciphertext image is successfully obtained. At this point, the encryption process of the entire image is successfully completed.

[0031] Among them, the scrambling and diffusion modules in the final encryption step here should be compatible, not only to adapt to the encoding requirements of different types of images, but also to accurately restore image information during decoding to avoid information loss or distortion. At the same time, the design of the scrambling and diffusion modules should be convenient for subsequent upgrades and expansions to cope with the ever-changing encryption technology requirements.

[0032] By adopting the above technical solution: on the one hand, in the initial condition setting stage, the present invention fully exploits the unique advantages of the chaotic system and carefully designs a set of complex and accurate algorithms. The algorithm comprehensively considers the rich and diverse basic data of the image itself, such as the resolution of the image, which not only determines the clarity and detail richness of the image, but is also closely related to the amount of data processing in the encryption process; the distribution of pixels, including the range and frequency of pixel values, contains the characteristics of the image texture, color, etc., which have an important impact on the encryption effect. In addition, the preset key constants are integrated into it, and the multidimensional data relationship is finely processed through matrix operations, and the inherent characteristics of the chaotic system are deeply excavated with the help of nonlinear function operations. After this series of rigorous and precise calculations, the initial conditions and parameter values ​​of the four-dimensional system, Arnold mapping and 2D-LSM can be accurately obtained. These initial conditions and parameter values ​​are like the "genetic code" of the encryption process, which gives the entire process a high degree of uncertainty and uniqueness from the starting point of the encryption process. This initial setting method that is closely combined with the characteristics of the image itself greatly enhances the pertinence and security of encryption, ensuring that the encryption effect can flexibly adapt to the encryption requirements of different images.

[0033] On the other hand, in the key generation process, iterative operations are carried out strictly based on cutting-edge chaotic dynamics rules. The initial conditions and parameter values ​​obtained by precise calculations in the early stage are connected to a powerful and efficient iteration engine. At the same time, with the help of advanced visualization methods, the gradual increase in the number of iteration steps and the bit-by-bit generation details of the key stream data from scratch and from simple to complex are displayed in real time and dynamically. In this way, the generated key stream has both high security and high randomness, just like casting an indestructible protective shield for the encryption process, making it difficult for external attackers to crack or predict the key stream by conventional means, providing reliable protection for subsequent encryption operations.

[0034] In the subsequent image transformation and final encryption steps, the present invention uses a variety of advanced image processing technologies to perform a full range of transformation processing on the plaintext image. First, the Arnold scrambling module is started to completely scramble the pixel positions of the plaintext image according to a specific mapping equation. The Arnold scrambling algorithm breaks the original positional association between pixels through a unique mathematical transformation, which fundamentally changes the spatial structure of the image, significantly increases the chaos of the image, and lays a good foundation for subsequent encryption operations. Next, the previously generated key stream is introduced, and the randomness and uniqueness of the key stream are used to accurately control the 2D-LSM diffusion module. The 2D-LSM diffusion module performs diffusion operations on the scrambled image based on its own characteristics and the control instructions of the key stream. In this process, the key stream is like an intelligent "commander", accurately controlling the direction and intensity of the diffusion, so that the correlation between image pixels is further reduced, the image features are fully blurred, and the security of encryption is greatly improved, and the intermediate image P2 is finally output.

[0035] Finally, in the final encryption phase, with the help of another key stream generated by the four-dimensional hyperchaotic system, the intermediate image P2 is scrambled and diffused at the decimal level. The scrambling algorithm is cleverly designed based on the characteristics of decimal numbers. By rearranging and combining the image data at the decimal level, the digital structure of the image is disrupted, further increasing the complexity of encryption. The diffusion operation makes full use of the randomness of the key stream to perform a full-scale and deep diffusion process on the image data, completely disrupting and confusing the information of the image data.

[0036] After this series of complex and rigorous operations, the originally ordered image data is converted into a ciphertext C that is extremely difficult to reverse restore. This final encryption method ensures that the ciphertext image C has extremely high security. Even in the face of the most advanced cracking technology and powerful computing power, it is difficult for external attackers to restore the original image through reverse engineering, thus providing indestructible protection for the image data.

[0037] In addition, the present invention also adopts a double hash function method, and comprehensively uses SHA-512 and MD5 algorithms to process 512-bit external keys and vectors related to images. In this way, the initial values ​​and parameters required for chaotic systems (such as 4D hyperchaotic systems, 2D Arnold mapping, and 2D-LSM) are generated. This key step further ensures the randomness and sensitivity of the chaotic system. Even if the image or key changes very slightly, it can cause significant changes in the parameters of the chaotic system, thereby enhancing the security of the encryption system in all directions.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The present invention can deeply integrate the four-dimensional hyperchaotic system with a variety of efficient image processing methods, aiming to overcome the shortcomings of the existing technology, achieve high security and high reliability of image encryption, effectively resist various possible attacks, and effectively protect the confidentiality and integrity of image data.

[0040] 2. The present invention can be widely used in digital images in many fields such as medical, military, finance, and security to provide solid security protection. In the medical field, electronic medical record images and medical imaging materials of patients contain extremely sensitive personal health information; intelligence images and strategic deployment maps in the military field are even more related to national security; transaction voucher images and customer information images in the financial industry are directly related to economic interests; and monitoring images in the security field are an important basis for maintaining social stability. The encryption method provided by the present invention can build a high-intensity and high-security protection barrier for these important image data to cope with the escalating information security threats. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is the overall flow chart of the present invention;

[0042] Figure 2 is a block diagram of the encryption process in the present invention;

[0043] Figure 3 This is a display effect diagram of an image encryption example in the present invention;

[0044] Figure 4 This is another display effect diagram of the image encryption example in the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0046] like Figure 1 As shown, a hybrid coding and encryption method for images based on a four-dimensional hyperchaotic system comprises the following steps:

[0047] Step 101: Generate Initial Conditions

[0048] In the specific implementation process, it is necessary to first comprehensively and accurately obtain the basic information of the image to be encrypted, which includes key data such as the size of the image and the pixel mean of each channel. The image size information directly reflects the size of the image, while the pixel mean reflects important attributes such as the overall brightness characteristics of the image. After obtaining this basic information, it is combined with the pre-set constant parameters, and then calculated through a specific and carefully designed algorithm to generate the initial conditions of the four-dimensional hyperchaotic system.

[0049] If we use a formula to express this process, we have:

[0050] IC=f(S,M,C)

[0051] Among them, IC represents the generated initial conditions, S represents the size information of the image, M represents the pixel mean, C represents the preset constant parameter, and f represents the algorithm function used to calculate the initial conditions.

[0052] The core purpose of this step is to provide an initial value that is both stable and closely related to the image's own characteristics for subsequent chaotic system iterations. In this way, the encryption process can fully combine the specific characteristics of the image, greatly enhance the pertinence and security of encryption, and ensure that the encryption effect can better adapt to the encryption needs of different images.

[0053] Step 102: Generate key stream

[0054] After the initial conditions are successfully generated, they are connected to a carefully constructed iteration engine. The iteration engine strictly follows the dynamic rules of the four-dimensional hyperchaotic system for iteration. In each iteration, the key stream fragments used for subsequent encryption links are generated according to the real-time output value of the chaotic system through a series of specific quantization and conversion operations. If the formula is used to describe this process in detail, it is:

[0055] KS i =g(X i )

[0056] Among them, KS i represents the key stream fragment generated in the iteration, S i represents the output value of the chaotic system in the i-th iteration, and g represents the quantization and conversion function.

[0057] During the entire key stream generation process, in order to ensure that the generated key stream has a high degree of randomness and security, strict control will be carried out through real-time monitoring of the number of iteration steps and various statistical characteristics of the key stream (such as randomness, uniformity, etc.). Only when the generated key stream meets the pre-set randomness and security standards can it enter the subsequent encryption process, thereby ensuring that the key stream can effectively play a strong protective role in the encryption process.

[0058] Step 103: Image preprocessing and encoding conversion

[0059] This step first reads and parses the plaintext image comprehensively and carefully, and converts it into a matrix form that is convenient for subsequent processing. Such a conversion makes it easier to perform various mathematical operations and transformations on the image data in subsequent encryption operations. After the conversion is completed, the image is preprocessed, such as normalization. Normalization can make the image pixel values ​​uniformly distributed within a specific range, eliminate the encryption interference that may be caused by differences in pixel value ranges between different images, and provide a more standardized data basis for subsequent encoding transformations.

[0060] Subsequently, a variety of advanced coding techniques, such as Arnold transform, two-dimensional logical self-mapping, etc., are used to perform comprehensive coding transformation on the preprocessed image. Taking Arnold transform as an example, its transformation formula is:

[0061]

[0062] Among them, (x, y) represents the coordinates of the original image pixel, (x new ,y new ) represents the coordinates of the transformed pixel, a and b are the transformation parameters, and N is the size of the image.

[0063] This formula can effectively disrupt the original arrangement order of image pixels and change the positional relationship between pixels, thereby increasing the degree of confusion of the image.

[0064] In addition to the Arnold transform, other encoding techniques such as two-dimensional logical self-mapping are also applied to perform multiple rounds of multi-angle encoding transformations on the image. After this series of complex and sophisticated encoding transformation operations, the pixel arrangement and feature structure of the image are completely disrupted, and the image after preliminary transformation is obtained, which lays a good foundation for subsequent encryption operations.

[0065] Step 104: Final encryption operation

[0066] The key stream carefully generated in step 102 is deeply fused and encrypted with the image obtained in step 103 after multiple rounds of transformation. The specific encryption method is to perform XOR operations, permutation operations, etc. on the transformed image pixels according to the value of the key stream at each coordinate position. These operations can completely disrupt the image information and achieve effective encryption of the image.

[0067] If the encryption process is expressed in a formula, it is:

[0068]

[0069] Among them, C (x,y)represents the pixel value of the encrypted image at the (x, y) coordinate, T (x,y) Represents the pixel value of the transformed image at the (x,y) coordinate, Indicates XOR operation, KS (x,y) Represents the key stream value at the corresponding coordinate.

[0070] After completing the above complete and rigorous steps, the final ciphertext image is successfully obtained. At this point, the encryption process of the entire image is successfully completed.

[0071] The present invention will be described in further detail below in conjunction with the embodiments.

[0072] Example

[0073] Figure 2 The flowchart of each module of the image encryption method is shown. The image encryption process of this embodiment will be described in detail below in conjunction with these figures.

[0074] First, a color image with a specific resolution is selected as the image to be encrypted for this encryption operation. Then, professional image analysis technology is used to accurately extract the size information of the image, including the length and width of the image; at the same time, the pixel mean of each channel (such as red, green, and blue channels) is deeply analyzed to fully grasp the basic characteristics of the image. After obtaining this basic information, it is combined with the pre-set constant parameters according to the preset rules, and the calculation is strictly carried out according to the algorithm in step 101. After complex and precise calculations, the initial conditions of the four-dimensional hyperchaotic system are generated.

[0075] Secondly, the generated initial conditions are accurately input into a carefully constructed iteration engine. The iteration engine strictly follows the dynamics of the four-dimensional hyperchaotic system and performs iterations in an orderly manner. During the entire iteration process, the generation of the key stream is closely monitored through a real-time monitoring system. After 1,000 carefully controlled iterations, a key stream that meets the requirements of high randomness and strict security is successfully generated.

[0076] Next, the plaintext image is deeply read and parsed, and converted into a matrix form that is easy to process. In order to further optimize the image data, the image is first normalized so that the image pixel values ​​are standardized and distributed within a specific range. On this basis, encoding techniques such as Arnold transformation and two-dimensional logical self-mapping are cleverly applied in sequence to perform a full range of encoding transformations on the image. After this series of complex transformation operations, the image after preliminary transformation is obtained, at which time the pixel arrangement and feature structure of the image have changed significantly.

[0077] Finally, the generated key stream is deeply fused and encrypted with the transformed image. Strictly following the encryption method in step 104, each pixel of the image is carefully operated one by one. Through this series of rigorous and delicate encryption steps, the ciphertext image is finally successfully obtained.

[0078] It can be clearly seen from the above detailed description that the method provided by the present invention can efficiently and reliably realize high-security encryption of images. From the generation of initial conditions, to the generation of key streams, to image preprocessing, encoding conversion and the final encryption operation, each step is closely linked and closely linked to ensure the security of image data.

[0079] Figure 3 The following is a display effect diagram of an image encryption example, wherein (a) is an original landscape image, which contains rich elements such as a vast blue sky, verdant mountains and dense forests, and has various color levels. (b) is a histogram of the original image, in which the red curve represents the distribution of red channel pixel values, which has a relatively small number of pixels in the low intensity value range (0-50) and a certain peak value in the high intensity value range (150-250), reflecting the distribution of red elements such as red flowers or sunset in the image; the green curve represents the distribution of green channel pixel values, which is more concentrated in the medium and low intensity value range (50-150), which is consistent with the pixel value characteristics of a large number of green vegetation in the image; the blue curve represents the distribution of blue channel pixel values, which has a higher number of pixels in the high intensity value range (200-300), corresponding to the blue sky part in the image. (c) is an image encrypted using the method of the present invention, which has a noise-like appearance, completely loses the identifiable information and visual features of the original image, and effectively hides the image content. (d) is the histogram of the encrypted image. Compared with the histogram of the original image, the pixel values ​​of each color channel in the encrypted image histogram are more evenly distributed. The red, green, and blue curves fluctuate smoothly in the entire [0-300] pixel intensity value range, without obvious peaks or concentrated areas, indicating that the encryption process successfully destroys the pixel value distribution law of the original image and enhances security. (e) is the decrypted image. By comparison, it can be found that the decrypted image is almost completely consistent with the original image visually, verifying the good reversibility of the encryption algorithm of the present invention, ensuring that the image data can be accurately restored and used by legitimate users after encrypted transmission or storage.

[0080] Figure 4Another effect diagram showing an example of image encryption, (a) is an original image of an animal, such as a zebra on the grassland, which has distinct black and white stripes and the colors of the surrounding environment. (b) is the histogram of the original image, in which the red channel pixel values ​​are distributed in a specific interval, reflecting the red elements in the animal's fur or the surrounding environment. The distribution of the green channel and blue channel pixel values ​​also each presents characteristics related to the image content. (c) is the image encrypted using the method of the present invention, which also appears noisy and the original image information cannot be identified. (d) is the histogram of the encrypted image, which has a uniform distribution characteristic. (e) is the decrypted image, which is highly similar to the visual effect of the original image, further proving the effectiveness and reliability of the encryption method of the present invention on different types of images.

[0081] After encryption, the original image becomes an encrypted image. It can be clearly seen that the encrypted image presents a noise-like appearance and completely loses the identifiable information and visual features of the original image. This shows that the encryption algorithm successfully obfuscates and hides the content of the original image, making it impossible for unauthorized users to obtain any meaningful information from the encrypted image, thereby ensuring the confidentiality of the image data.

[0082] The histogram corresponding to the encrypted image shows that the encrypted image histogram presents a relatively uniform distribution. Compared with the original image histogram, the pixel values ​​of each color channel in the encrypted image histogram are more evenly distributed, without obvious peaks or concentrated areas. This uniform distribution characteristic shows that the encryption process effectively destroys the pixel value distribution law of the original image, further enhancing the security of the encrypted image, making it difficult for attackers to crack the encrypted image through statistical analysis and other means.

[0083] Finally, the restored image after the decryption operation is shown. It can be seen that the decrypted image is almost completely consistent with the original image visually, which proves that the proposed encryption algorithm has good reversibility and can accurately restore the encrypted image to the original image, ensuring that the image data can be correctly decrypted and used by legitimate users after encrypted transmission or storage without causing information loss or distortion.

[0084] In summary, Figure 3 , Figure 4 By displaying the original image, encrypted image and their related histograms, as well as comparing the decrypted images, the excellent performance of the proposed encryption method in image encryption, confidentiality and reversibility is fully verified, providing strong support and proof for the reliability and security of the encryption technology in practical applications.

[0085] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A hybrid coding and encryption method for images based on a four-dimensional hyperchaotic system, characterized in that: The steps include: Step 101: According to a preset algorithm, using basic image information or preset constants, through complex mathematical operations, accurately calculate the initial conditions and parameter values ​​of the four-dimensional system, Arnold mapping, and two-dimensional logical self-mapping 2D-LSM, so as to provide accurate starting settings for subsequent encryption processes. The complex mathematical operations include matrix operations and nonlinear function calculations to ensure that the obtained initial conditions and parameter values ​​are unique and stable to adapt to different image characteristics and encryption requirements. Step 102: Import the initial conditions and parameter values ​​calculated in step 101 into the iteration module, perform iterative operations based on the built-in chaotic dynamics rules, and display the number of iteration steps and the dynamic generation of the key stream in real time during the iteration process to generate an encryption key stream with high randomness and high strength. The generation mechanism of the key stream ensures that it has sufficient complexity, making it difficult for the outside to crack or predict it through conventional means. The algorithm design of the iteration module should ensure the difference of the key stream in different encryption cycles on the previous day; Step 103: Use the formula to replace the relevant parameters, drive the Arnold scrambling module to scramble the pixel positions of the plaintext image P, and the scrambling method is based on the scrambling algorithm to ensure that the original arrangement order of the pixels is effectively destroyed to obtain a preliminary transformed image; then, introduce the key stream generated in step 102 and the 2D-LSM diffusion module, use the key stream to control the diffusion direction and intensity, combine the characteristics of 2D-LSM to perform a diffusion operation on the scrambled image, further blur the image features, and output the intermediate image P2. In this process, the parameter setting of the diffusion module should be closely coordinated with the key stream to achieve the best image blurring effect; Step 104: With the help of another key stream generated by the four-dimensional hyperchaotic system, the intermediate image P2 is scrambled and diffused at the decimal level. The scrambling algorithm is designed based on the characteristics of decimal numbers. The diffusion operation uses the randomness of the key stream to completely disrupt the image data structure and successfully output the ciphertext image C. The design of the entire final encryption step ensures that the ciphertext image C is secure and it is difficult for an outsider to restore the original image through reverse engineering.

2. According to claim 1, a method for hybrid coding and encryption of images based on a four-dimensional hyperchaotic system is characterized in that: In step 101, it is necessary to first obtain the basic information of the image to be encrypted comprehensively and accurately, wherein the basic information includes the size S of the image and the pixel mean M of each channel; combine it with the preset constant parameter C, and then calculate it through the following algorithm f to generate the initial conditions of the four-dimensional hyperchaotic system. This process can be expressed by the formula: IC=f(S,M,C) Among them, IC represents the generated initial conditions, S represents the size information of the image, M represents the pixel mean, C represents the preset constant parameter, and f represents the algorithm function used to calculate the initial conditions.

3. The method for hybrid coding and encryption of images based on a four-dimensional hyperchaotic system according to claim 1 is characterized in that: In step 102, after the initial conditions are successfully generated, they are connected to the constructed iteration engine; the iteration engine strictly performs iteration operations according to the dynamics rules of the four-dimensional hyperchaotic system; in each iteration process, the key stream fragments for subsequent encryption links are generated according to the real-time output value of the chaotic system through quantization and conversion operations; the formula used to specifically describe this process is: KS i =g(X i ) Among them, KS i represents the key stream fragment generated by the i-th iteration, S i represents the output value of the chaotic system in the i-th iteration, g represents the quantization and conversion function; X i is the state vector of the four-dimensional hyperchaotic system at the th iteration.

4. The method for hybrid coding and encryption of images based on a four-dimensional hyperchaotic system according to claim 1 is characterized in that: In step 103, the plaintext image is first read and parsed, and converted into a matrix form that is convenient for subsequent processing; after the conversion is completed, the image is preprocessed, such as normalized; Subsequently, coding techniques such as Arnold transform and two-dimensional logical self-mapping are used to perform comprehensive coding transformation on the preprocessed image. Taking Arnold transform as an example, the transformation formula is: Among them, (x, y) represents the coordinates of the original image pixel, (x new ,y new ) represents the coordinates of the transformed pixel, a and b are the transformation parameters, and N is the size of the image.

5. The method for hybrid coding and encryption of images based on a four-dimensional hyperchaotic system according to claim 1 is characterized in that: In step 104, the key stream generated in step 102 and the image obtained in step 103 after multiple rounds of transformation are deeply fused and encrypted; the specific encryption method is to perform XOR operation and permutation operation on the transformed image pixels according to the value of the key stream at each coordinate position, and these operations can completely disrupt the image information and realize effective encryption of the image; the encryption process is expressed by the formula: Among them, C (x,y) represents the pixel value of the encrypted image at the (x, y) coordinate, T (x,y) Represents the pixel value of the transformed image at the (x,y) coordinate, Indicates XOR operation, KS (x,y) Indicates the key stream value at the corresponding coordinate; After the above steps, the final ciphertext image is successfully obtained. At this point, the encryption process of the entire image is successfully completed.

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