Double encryption image protection method based on chaotic mapping and linear congruence method

Abstract

The invention discloses a double encryption image protection method based on chaotic mapping and a linear congruence method, and the method specifically comprises the following steps: S1, obtaining a to-be-encrypted image, and converting the image into a data sequence; s2, performing image sequence scrambling on the data sequence based on an AES encryption algorithm to obtain a first to-be-encrypted sequence; s3, constructing a chaotic system to generate a chaotic sequence, and performing mapping encryption on the chaotic sequence to obtain a key sequence; and S4, performing XOR operation on the first to-be-encrypted sequence and the key sequence, and outputting an encrypted sequence.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing, and particularly to a dual-encryption image protection method based on chaotic mapping and the linear congruence method. Background Art

[0002] With the rapid development of computer networks, the number of pictures transmitted over the network is increasing, which has drawn people's attention to the secure transmission of pictures. Nowadays, scholars at home and abroad attach great importance to encrypting pictures during image transmission. Traditional encryption methods may face risks of relatively low security and being vulnerable to external interference.

[0003] Existing technologies generally adopt image encryption methods based on chaotic sequences. Existing solutions include:

[0004] The invention patent "Novel Eighth-Order Hyperchaotic System and Its Method for Encryption and Decryption in Images" (Application No.: 202311109735.3). This invention uses a complex hyperchaotic equation as a pseudo-random sequence generator to separate the RGB channels of an image, perform row-column scrambling and diffusion operations, thereby achieving image encryption. The decryption process of this system is the reverse operation of the encryption step, using the same sequence to restore the image in reverse order, ensuring the security and effectiveness of encryption, while enhancing the ability to resist various attacks. However, due to the use of an eighth-order hyperchaotic equation, this system involves a relatively complex calculation process, which will result in high computational resource consumption, especially in application scenarios that require fast encryption and decryption. For the need of real-time image encryption and decryption, the high complexity of this system will lead to processing delays and is not suitable for applications that require instant response. Implementing such a high-order hyperchaotic encryption system requires more powerful hardware support to handle complex algorithms and large amounts of data operations, which will increase the cost of system deployment.

[0005] The invention patent "A High-Dimensional Hyperchaotic Image Encryption Method Combining Arnold Transformation and DNA Hybrid Coding Scrambling" (Application No.: 202311331535.2). This technical solution involves converting the original image into a pixel matrix, processing these matrices through Arnold transformation and an eight-dimensional sixth-order hyperchaotic system to generate multiple intermediate matrices. These matrices undergo DNA coding and operations to finally obtain the encrypted image. This method improves the complexity and security of image encryption by combining the spatial scrambling of Arnold transformation and the numerical scrambling of DNA coding. This solution using an eight-dimensional hyperchaotic system and Arnold transformation results in high computational complexity and memory consumption, which is not suitable for application scenarios that require fast processing. Integrating Arnold transformation, DNA coding, and the hyperchaotic system requires precise parameter adjustment and strict synchronization, which increases the complexity of implementation.

[0006] Patent for Invention "A Compressible Six-Dimensional Non-Degenerate Hyperchaotic Image Security System and Method" (Authorization Number: 202111180734.9). In this solution, image data is first compressed to generate a compression coefficient matrix. Then, a six-dimensional hyperchaotic system is used to generate a chaotic sequence to encrypt the compressed data and form ciphertext. At the decryption end, the same hyperchaotic sequence is used for reverse operation to restore the original compressed data, and finally the original image is restored through decompression. This system utilizes the high randomness of the hyperchaotic system and SOPC resources to parallelly accelerate the chaotic discretization process in the FPGA, improving the working efficiency and security of the image security system. The implementation of this invention depends on the highly integrated six-dimensional hyperchaotic system and SOPC, which is relatively complex and requires high technical skills. Since a large amount of FPGA and SOPC resources are used in the system design, it will result in higher hardware costs and dependence on specific hardware. Although image data compression and parallel processing technologies are used, the high-dimensional hyperchaotic system itself will cause high consumption of computing resources. The operation of the system highly depends on the preset hardware configuration and algorithm design, which limits its flexible adaptability in different application scenarios.

[0007] Patent for Invention "A Novel Hyperchaotic Image Encryption Method" (Authorization Number: 201610908104.1). This invention involves three key steps: key initialization, scrambling transformation, and Hyperhenon hyperchaotic mapping diffusion. The initial key consists of a binary auxiliary key and an input key, and a hyperchaotic sequence is generated through the Hyperhenon mapping for diffusion operation. The image is first segmented into multiple column vector groups, bitized, and then scrambled using the Arnold mapping to generate intermediate ciphertext. Then, the hyperchaotic sequence is used for diffusion operation with the intermediate ciphertext to generate the final ciphertext. This method can effectively improve the security of image encryption and resist statistical feature attacks and differential attacks. This encryption method involves multi-step operations, including bitization processing, scrambling operation, and chaotic sequence generation, etc., and each step requires precise calculation and control, with complex implementation. Due to the use of high-dimensional chaotic mapping and multiple iterative operations, it will result in high computational overhead, affecting the encryption and decryption speed, especially when dealing with large-scale image data. The high computational requirements may require strong hardware support, increasing the implementation cost, especially when deployed on resource-constrained devices. Summary of the Invention

[0008] Aiming at the problem of low security of image encryption in the prior art, the present invention proposes a dual-encryption image protection method based on chaotic mapping and linear congruence method. By introducing a chaotic sequence, the randomness and unpredictability of the key are improved, thereby greatly enhancing the security and anti-interference ability of image encryption.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A dual - encryption image protection method based on chaotic mapping and the linear congruence method, specifically including the following steps:

[0011] S1: Obtain the image to be encrypted and convert the image into a data sequence;

[0012] S2: Perform image sequence scrambling on the data sequence based on the AES encryption algorithm to obtain the first sequence to be encrypted;

[0013] S3: Construct a chaotic system to generate a chaotic sequence, and perform mapping encryption on the chaotic sequence to obtain a key sequence;

[0014] S4: Perform an exclusive - OR operation on the first sequence to be encrypted and the key sequence, and output the encrypted sequence.

[0015] Preferably, the S1 includes:

[0016] S1 - 1: Decompose the image to be encrypted into d matrices, where the size of the matrix is w * h; where w represents the length of the image, h represents the width of the image, and d represents the number of channels of the image;

[0017] S1 - 2: Convert each matrix into a corresponding column vector by rows, and then connect the column vectors in sequence to form a data sequence.

[0018] Preferably, the S2 includes:

[0019] S2 - 1: Perform calculations on the data sequence based on the AES encryption algorithm to obtain the corresponding inverse element;

[0020] S2 - 2: Perform an affine transformation on the obtained inverse element to obtain transformation parameters;

[0021] S2 - 3: Use the transformation parameters as new output bytes to form entries in the S - box, that is, the first sequence to be encrypted.

[0022] Preferably, in the S2 - 1, map the zero element of the data sequence to the fixed value 0x63.

[0023] Preferably, in the S2 - 2, the formula for the affine transformation is:

[0024] w = A·θ + b (1)

[0025] In formula (1), w represents the transformation parameter; A is a fixed 8×8 linear transformation matrix; b is a constant vector; θ represents the inverse element.

[0026] Preferably, the S3 includes:

[0027] S3 - 1: Construct a chaotic system;

[0028] S3-2: Generate a chaotic sequence based on the constructed chaotic system;

[0029] S3-3: Map the chaotic sequence to a preset interval to obtain a mapped sequence;

[0030] S3-4: Quantize the mapped sequence by 16 bits to obtain the key sequence G.

[0031] Preferably, in the above S3-1, the chaotic system is:

[0032]

[0033] In formula (2), x, y, and z represent the state variables of the chaotic system.

[0034] Preferably, the above S3-2 includes:

[0035] S3-2-1: Pre-iterate the chaotic system N 1 times;

[0036] S3-2-2: Then iterate the chaotic system N 2 times to generate a new set of state values A = A x , A y , A z , where A x = x 1 , x 2 ,..., x k , A y = y 1 , y 2 ,..., y k , A z = z 1 , z 2 ,..., z k , 0 < k ≤ P; x k , y k , z k represent the state values of each variable in the k-th iteration of the chaotic system, and P represents the length of the sequence to be encrypted divided by 3;

[0037] S3-2-3: According to the positive and negative changes of the product between the variables of the state variable A, adjust the order of the state variables to generate the chaotic sequence C = C 1 , C 2 ,..., C k ; C k represents the chaotic result of the k-th iteration of the chaotic system.

[0038] Preferably, in the above S3-3, the input value of the chaotic sequence is mapped to the preset interval [0, 1] by the linear congruence method to obtain the mapped sequence:

[0039] q = a·ε + T mod m (3)

[0040] In formula (3), q represents the mapping sequence value; a represents the multiplier; T represents the increment; mod m represents the modulus; ε represents the input value of the chaotic sequence.

[0041] Preferably, in S4, the calculation of the encryption sequence is as follows:

[0042] First, perform exclusive OR operations on the high 8 bits and the low 8 bits of the first encryption sequence I and the key sequence G respectively to obtain the first calculation result and the second calculation result:

[0043] I n = i 1 , i 2 ,..., i f / 2 , G n = g 1 , g 2 ,..., g f / 2 (4)

[0044] In formula (4), I n represents the first calculation result; i f / 2 represents the binary bit of the first encryption sequence I n ; G n represents the second calculation result; g f / 2 represents the binary bit of the key sequence G;

[0045] Then, based on the exclusive OR operation, encrypt the first calculation result to obtain the encryption result, and splice multiple encryption results to obtain the encryption sequence:

[0046]

[0047] In formula (5), E n represents the encryption result, G kH represents the high f / 2 sub-sequence of the chaotic key sequence G; G kL represents the low f / 2 sub-sequence of the chaotic key sequence G; represents the exclusive OR operation.

[0048] In summary, due to the adoption of the above technical solutions, compared with the prior art, the present invention has at least the following beneficial effects:

[0049] The present invention combines a chaotic system and the linear congruence method to achieve higher security and anti-interference ability through double encryption.

[0050] The chaotic system has a high degree of randomness and unpredictability, providing additional security for key generation;

[0051] Based on the design of a three-dimensional improved Lorenz chaotic system, the calculated Lyapunov exponents indicate that it has significant chaotic characteristics, thus enhancing the randomness and complexity of the encryption algorithm;

[0052] Adopt a simple and easy-to-implement algorithm (such as XOR operation), avoiding complex calculations and anti-saturation processing, while ensuring that the encryption and decryption processes are consistent;

[0053] While providing efficient encryption, it significantly reduces hardware requirements and is suitable for a wide range of application scenarios;

[0054] The sensitivity of the chaotic sequence to the initial conditions provides an additional security level for image encryption, and it can effectively resist various attack methods such as differential attacks and statistical feature attacks, improving security;

[0055] It has a strong resistance to random interference and noise, and is particularly suitable for scenarios with high reliability requirements such as military communications and security monitoring;

[0056] The chaotic system in the design has good scalability, can adapt to different encryption requirements, and supports multi-dimensional and multi-scenario applications;

[0057] This method is completely software-based and does not require additional hardware costs, enhancing the economy in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of a dual-encryption image protection method based on chaotic mapping and linear congruence method according to an exemplary embodiment of the present invention.

[0059] Figure 2 It is a schematic diagram of the process of decomposing a three-channel image to be encrypted into data sequences according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] The present invention will be further described in detail below in conjunction with embodiments and specific implementation manners. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0061] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0062] In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "installation", "connection", and "linkage" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two components. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0063] As Figure 1 shown, the present invention provides a dual - encryption image protection method based on chaotic mapping and the linear congruence method, which specifically includes the following steps:

[0064] S1: Obtain the image to be encrypted and convert the image into a data sequence.

[0065] As Figure 2 shown, it specifically includes:

[0066] S1 - 1: Decompose the image to be encrypted (for example, a three - channel RGB image) into d matrices, where the size of the matrix is w * h; where w represents the length of the image, h represents the width of the image, and d represents the number of channels of the image.

[0067] S1 - 2: Convert each matrix into a corresponding column vector by row, and then connect the column vectors in sequence (for example, connect them head - to - tail) to form a complete data sequence.

[0068] S2: Perform image sequence scrambling on the data sequence based on the AES encryption algorithm to obtain the first sequence to be encrypted.

[0069] S2 - 1: Perform calculations on the data sequence in the finite field GF(2 8 ) of the AES encryption algorithm to obtain the corresponding inverse element.

[0070] For each input byte (referring to the data sequence output by S1), first find its inverse element in the finite field GF(2 8 ) to construct the S - box. The inverse element means that for a given element x, there exists an element x -1 , such that their product is 1, that is: x·x -1 = 1.

[0071] In this embodiment, the S - box (Substitution Box) is an important component in the AES algorithm. It increases the complexity of the cipher by applying a non - linear substitution operation to each data block (byte), making the encryption more difficult to be cracked through simple linear analysis.

[0072] The AES encryption process consists of multiple steps, one of which is scrambling using the S-box. In the AES algorithm, the role of the S-box is to perform byte substitution operations during the encryption process, replacing each input byte (a number between 0 - 255) with a new byte to form a new data block.

[0073] 1. Structure of the S-box

[0074] AES uses a fixed S-box for byte substitution operations. This S-box is a non-linear substitution table that maps each byte (8 bits, 0 - 255). The design of the S-box is based on a mathematically irreversible function. Specifically, it uses the inverse element operation in GF(2^8) (finite field) and an affine transformation.

[0075] The construction process of the S-box includes the following steps:

[0076] Inverse element: First, the input value of the AES S-box is regarded as an element in GF(2^8), and the inverse element of this element is calculated (in the finite field).

[0077] Affine transformation: Then, the inverse element undergoes an affine transformation (linear transformation plus a constant) to obtain the final S-box output.

[0078] 2. Construction process of the S-box

[0079] Suppose we want to encrypt a byte x (the value range is 0 to 255). First:

[0080] Regard x as an element in the finite field GF(2^8).

[0081] Perform an inverse operation on x to obtain its inverse element in GF(2^8).

[0082] Perform an affine transformation on the obtained inverse element to obtain the S-box output through a predefined matrix and constant.

[0083] The design of the S-box makes the relationship between its output and input highly non-linear, which provides security for AES.

[0084] 3. S-box scrambling in AES

[0085] During the AES encryption process, S-box scrambling appears in the SubBytes step. This step operates on each byte as follows:

[0086] SubBytes: For each byte x, look up the corresponding value S(x) in the S-box and replace the original byte with the value at the corresponding position in the S-box. The purpose of this step is to break the linear structure of the input bytes and make the ciphertext more random.

[0087] For example, if the input block contains the byte 0x32, after looking up through the S-box, it may be replaced by 0x87. This byte substitution is irreversible, thus increasing the strength of the cipher.

[0088] 4. Application of the S-box in the AES encryption process

[0089] In the encryption process of AES, the S-box scrambling is achieved through multiple rounds of the SubBytes step. In each round, the input data (data block) is decomposed into multiple bytes, and each byte is replaced through the S-box. The specific process is as follows:

[0090] Initial Round Key Addition (AddRoundKey): Perform an exclusive OR operation on the input data and the round key.

[0091] SubBytes: Apply S-box substitution (scrambling) to each byte.

[0092] ShiftRows: Perform a cyclic shift on the data rows.

[0093] MixColumns (only in all rounds except the last round): Perform a matrix transformation on the data columns to increase the diffusion of the data.

[0094] AddRoundKey: Perform an exclusive OR operation with the round key again.

[0095] These steps are repeated for multiple rounds until the final encrypted ciphertext is obtained.

[0096] In this embodiment, the core design of the S-box is to enhance the nonlinearity of the encryption. In the AES algorithm, the role of the S-box scrambling is as follows:

[0097] Improve cipher complexity: By replacing the input bytes with other bytes, the S-box disrupts the structure of the data, making the relationship between the output and the input very complex. Without the appropriate key, it is impossible to predict the output value.

[0098] Enhance anti-attack ability: The nonlinear characteristics of the S-box are crucial for resisting linear attacks, differential attacks, and other mathematical attacks.

[0099] Increase encryption strength: The S-box provides an irreversible transformation, making it difficult to reverse-derive the original data or key even if some bytes in the encryption process are analyzed.

[0100] The S-box design of AES highly emphasizes security and employs many mathematical techniques to ensure strong anti-attack capabilities. The S-box design enhances security in the following ways:

[0101] Unpredictability: The S-box is carefully designed to ensure that the output of each byte substitution operation is unpredictable, reducing direct inference of the original data.

[0102] Resistance to differential attacks: Differential attack is a way to crack the key by analyzing the differences between the input and output during the encryption process. The S-box of AES avoids patterns that are easily exploited by differential attacks during design, thereby enhancing its resistance to differential attacks.

[0103] Resistance to linear attacks: Linear attacks rely on finding linear relationships between the input and output. The S-box of AES makes such attacks very difficult through its highly non-linear substitution behavior.

[0104] In this embodiment, calculating the inverse element of the input byte requires using the multiplication rules of the finite field GF(2 8 ) and is achieved by solving a specific polynomial (which is prior art and will not be elaborated here).

[0105] In this embodiment, in the finite field GF(2 8 ), the zero element 0x00 has no inverse element. Therefore, during the construction of the S-box, the zero element is specially processed and usually mapped to a fixed value 0x63 to avoid errors.

[0106] S2-2: Perform an affine transformation on the obtained inverse element to obtain transformation parameters.

[0107] In this embodiment, a fixed linear affine transformation is used to further scramble the structure of the inverse element. The formula for the affine transformation is:

[0108] w = A·θ + b (1)

[0109] In formula (1), w represents the transformation parameter; A is a fixed 8×8 linear transformation matrix; b is a constant vector, and θ represents the inverse element. The purpose of the affine transformation is to enhance the unpredictability and resistance to linear attacks of the S-box, making the output of the S-box not easily derivable through simple linear relationships.

[0110] S2-3: Use the transformation parameter as the new output byte to form an entry in the S-box.

[0111] In this embodiment, after the above steps (S2-1, S2-2, S2-3), an output byte corresponding to each input byte (from 0 to 255) is generated. The entire S-box is a lookup table of size 256, containing the mapping from input bytes to output bytes. In this way, the scrambling operation of the image sequence is realized, which is also the primary encryption of the image sequence, and the first encrypted sequence I is obtained.

[0112] S3: Construct a chaotic system to generate a chaotic sequence, and perform mapping encryption on the chaotic sequence to obtain a key sequence.

[0113] S3-1: Construct a chaotic system.

[0114] Chaos phenomenon is a deterministic and quasi-random process manifested in nonlinear dynamic systems. This process is neither periodic nor convergent, and has a sensitive dependence on the initial value. Its behavior is characterized by uncertainty, non-repeatability, and unpredictability.

[0115] Based on the three-dimensional improved Lorenz chaotic system, the present invention constructs a new three-dimensional chaotic system:

[0116]

[0117] In formula (2), x, y, and z represent the state variables of the chaotic system. The Lyapunov exponents can be calculated to determine whether the system has chaotic characteristics. Since the Lyapunov exponent is an important indicator for quantifying the sensitivity of the system to the initial conditions, a positive Lyapunov exponent indicates that the system has exponential sensitivity to small changes in the initial conditions, and this behavior is a typical characteristic of a chaotic system.

[0118] For the constructed chaotic system, through numerical analysis, the calculated Lyapunov exponents are 3.2221, 0, -21.2458, which means that the constructed chaotic system has chaotic characteristics. The present invention generates a chaotic sequence based on this new chaotic system.

[0119] S3-2: Generate a chaotic sequence based on the constructed chaotic system.

[0120] Due to the high randomness and complexity of the chaotic system, the chaotic sequence is transformed into the required form through a specific quantization algorithm, enhancing the security of the encryption algorithm. The specific operations are as follows:

[0121] S3-2-1: Pre-iterate the chaotic system N 1 times to eliminate the transient influence of the chaotic system entering the chaotic state.

[0122] S3-2-2: Then iterate the chaotic system N 2Next, generate a new set of state values \(A = A\) x , \(A\) y , \(A\) z , where \(A\) x = \(x\) 1 , \(x\) 2 ,..., \(x\) k , \(A\) y = \(y\) 1 , \(y\) 2 ,..., \(y\) k , \(A\) z = \(z\) 1 , \(z\) 2 ,..., \(z\) k , \(0 \lt k \leq P\); \(x\) k , \(y\) k , \(z\) k represent the state values of each variable in the \(k\)-th iteration of the chaotic system, and \(P\) represents the length of the sequence to be encrypted divided by 3.

[0123] S3-2-3: According to the positive and negative changes of the product between the variables of the state variable \(A\) (such as \(x\) k \(\cdot y\) k , \(x\) k \(\cdot z\) k , \(z\) k \(\cdot y\) k ), adjust the order of the state variables to generate a chaotic sequence \(C = C\) 1 , \(C\) 2 ,..., \(C\) k , \(C\) k represents the chaotic result of the \(k\)-th iteration of the chaotic system. The mapping relationship between the sorting rule of the chaotic sequence \(C\) and the state variable \(A\) is shown in Table 1.

[0124] Table 1 Mapping relationship between the sorting rule of the chaotic sequence \(C\) and the state variable \(A\)

[0125]

[0126] S3-3: Map the chaotic sequence to a preset interval to obtain a mapped sequence.

[0127] Since the value range of the chaotic sequence generated by S3-2 is relatively large and it cannot be effectively controlled within the range of \([0,1]\), this will have an adverse impact on the next chaotic encryption (in the XOR operation, the input value range is preferably between \([0,1]\), which can avoid the scaling problem of detecting the input value). Therefore, the input value of the chaotic sequence is mapped to the preset interval \([0,1]\) by the linear congruence method, which can further improve the nonlinearity of the chaotic sequence.

[0128] In this embodiment, the objective function of the linear congruence method is as follows:

[0129] q = a·ε + T mod m (3)

[0130] In formula (3), the values of a, T, and mod m directly affect the quality, periodicity, and algorithm efficiency of the generated mapping sequence. Mod m represents the modulus, usually a large prime number to ensure a long period, and a common value is 232; the value of the multiplier a can ensure that the generated sequence has good periodicity and uniformity, and a common value is 1664525; the increment T also affects the generation quality of the sequence, and usually a non-zero value is selected and relatively prime to the modulus m to avoid generating duplicate sequences, and a common value is 1; ε represents the input value of the chaotic sequence; q represents the mapping sequence value.

[0131] S3-4: Quantize the mapping sequence by 16 bits to obtain the key sequence G.

[0132] S4: To demonstrate the simplicity and non-linear advantages of chaotic keys, give full play to the advantages of ciphertext interleaving and diffusion technology in image encryption, and improve its ability to resist illegal attacks, the present invention uses the exclusive OR operation method for image encryption. Its characteristics are suitable for image signal encryption, non-linear ciphertext, easy to implement, and can improve the ciphertext diffusion speed.

[0133] Perform exclusive OR operations on the high 8 bits and low 8 bits of the first encryption sequence I and the key sequence G respectively to obtain the first calculation result and the second calculation result:

[0134] I n = i 1 , i 2 ,..., i f / 2 , G n = g 1 , g 2 ,..., g f / 2 (4)

[0135] In formula (4), I n represents the first calculation result; i f / 2 represents the binary bit of the first encryption sequence I n ; G n represents the second calculation result; g f / 2 represents the binary bit of the key sequence G; f = 16.

[0136] For example, if I n is 8 bits, it is represented as i 1 , i 2 ,..., i 8 , i 1 , i 2 ,..., i 8 The values of are 0 or 1. Since the operation of equation (5) is bitwise exclusive OR operation, this is for convenient description.

[0137] Then, based on the XOR operation, the first calculation result is used for image encryption to obtain an encryption result, and then multiple encryption results are concatenated (for example, connected end to end) to obtain an encryption sequence:

[0138]

[0139] In formula (5), E n represents the encryption result, G kH represents the high f / 2-bit subsequence of the chaotic key sequence G; G kL represents the low f / 2-bit subsequence of the chaotic key sequence G; represents the XOR operation.

[0140] In the field of robot critical data privacy protection, the chaotic image encryption method of the present invention can ensure that sensitive data generated by a robot during task execution, such as operation instructions and sensor information, etc., is highly encrypted during storage or transmission. Even if the data is intercepted, it cannot be decrypted, effectively preventing data leakage and illegal access, and ensuring the security of enterprise and personal privacy.

[0141] In military communication, the secure transmission of image data is crucial. The chaotic image encryption method of the present invention can be applied to an unmanned aerial vehicle (UAV) image reconnaissance transmission system. The image information collected by the UAV is encrypted through the encryption method of the present invention before transmission. Even if the data is intercepted during transmission, it cannot be decrypted due to the high-level encryption protection, thus ensuring the security of sensitive information.

[0142] In the field of security monitoring, surveillance images often contain personal privacy or sensitive area information. By using the technology of the present invention, surveillance images are subjected to high-security-level encryption processing before storage or transmission. Even if the surveillance data is illegally accessed, the encryption technology can effectively prevent data leakage.

[0143] For image data involving personal privacy, such as medical images, the encryption technology of the present invention can be used to protect patient information from unauthorized access. Even if the encrypted image data is stolen during cloud storage or transmission, it cannot be illegally parsed, ensuring the security of personal information.

[0144] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present invention, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. A double encryption image protection method based on chaotic mapping and linear congruential method, characterized in that: The specific steps include: S1: Obtain the image to be encrypted and convert the image into a data sequence; S2: Perform image sequence scrambling on the data sequence based on the AES encryption algorithm to obtain a first sequence to be encrypted; S3: construct a chaotic system to generate a chaotic sequence, and map and encrypt the chaotic sequence to obtain a key sequence; S4: Perform an XOR operation on the first sequence to be encrypted and the key sequence, and output an encrypted sequence.

2. The method for protecting a double-encrypted image based on chaotic mapping and linear congruential method as claimed in claim 1, characterized in that: The S1 includes: S1-1: Decompose the image to be encrypted into d matrices, the size of the matrix is ​​w*h; where w represents the length of the image, h represents the width of the image, and d represents the number of channels of the image; S1-2: Convert each matrix into corresponding column vectors by row, and then connect the column vectors in sequence to form a data sequence.

3. The method for protecting a double-encrypted image based on chaotic mapping and linear congruential method as claimed in claim 1, characterized in that: The S2 includes: S2-1: Calculate the data sequence based on the AES encryption algorithm to obtain the corresponding inverse element; S2-2: Perform affine transformation on the obtained inverse element to obtain transformation parameters; S2-3: Use the transformation parameters as new output bytes to form an entry in the S-box, that is, the first sequence to be encrypted.

4. The method for protecting a double-encrypted image based on chaotic mapping and linear congruential method as claimed in claim 3, characterized in that: In S2-1, the zero element of the data sequence is mapped to a fixed value 0x63.

5. The method for protecting double-encrypted images based on chaotic mapping and linear congruential method as claimed in claim 3, characterized in that: In S2-2, the formula of affine transformation is: w=A·θ+b (1) In formula (1), w represents the transformation parameter; A is a fixed 8×8 linear transformation matrix; b is a constant vector; and θ represents the inverse element.

6. The method for protecting a double-encrypted image based on chaotic mapping and linear congruential method as claimed in claim 1, characterized in that: The S3 includes: S3-1: Constructing a chaotic system; S3-2: Generate chaotic sequences based on the constructed chaotic system; S3-3: Mapping the chaotic sequence to a preset interval to obtain a mapping sequence; S3-4: quantize the mapping sequence to 16 bits to obtain the key sequence G.

7. A double encryption image protection method based on chaotic mapping and linear congruential method as claimed in claim 6, characterized in that: In S3-1, the chaotic system is: In formula (2), x, y, and z represent the state variables of the chaotic system.

8. The method for protecting a double-encrypted image based on chaotic mapping and linear congruential method as claimed in claim 6, characterized in that: The S3-2 includes: S3-2-1: pre-iterate the chaotic system N1 times; S3-2-2: Then iterate the chaotic system N2 times to generate a new set of state values ​​A = {A x ,A y ,A z }, where A x ={x1,x2,...,x k }, A y ={y1,y2,...,y k }, A z ={z1,z2,...,z k },0 <k≤P;x k ,y k 、z k represents the state value of each variable of the chaotic system at the kth iteration, and P represents the length of the sequence to be encrypted divided by 3; S3-2-3: According to the positive and negative changes of the products of the variables in state variable A, adjust the order of state variables to generate a chaotic sequence C = {C1, C2, ..., C k }; C k Represents the chaotic result of the kth iteration of the chaotic system.

9. The method for protecting double-encrypted images based on chaotic mapping and linear congruential method as claimed in claim 6, characterized in that: In S3-3, the input value of the chaotic sequence is mapped to a preset interval [0,1] by a linear congruential method to obtain a mapping sequence: q=(a·ε+T)mod m (3) In formula (3), q represents the mapping sequence value; a represents the multiplier; T represents the increment; mod m represents the modulus; and ε represents the input value of the chaotic sequence.

10. The method for protecting a double-encrypted image based on chaotic mapping and linear congruential method as claimed in claim 1, characterized in that: In S4, the encryption sequence is calculated as: First, perform XOR operations on the high 8 bits and low 8 bits of the first encryption sequence I and the key sequence G to obtain the first calculation result and the second calculation result: I n ={i1,i2,...,i f / 2 },G n ={g1,g2,...,g f / 2 } (4) In formula (4), I n represents the first calculation result; i f / 2 Represents the first encryption sequence I n The binary bit of G n Indicates the second calculation result; g f / 2 Represents the binary bit of the key sequence G; Then, the first calculation result is encrypted based on the XOR operation to obtain the encrypted result, and then multiple encryption results are concatenated to obtain the encrypted sequence: In formula (5), E n Indicates the encryption result, G kH represents the high f / 2-bit subsequence of the chaotic key sequence G; G kL represents the low f / 2 bit subsequence of the chaotic key sequence G; Represents the exclusive-or operation.

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