Image encryption method based on ring rotation and generalized feistel cipher structure

Abstract

The application provides an image encryption method based on ring rotation and generalized Feistel cipher structure. The method comprises the following steps: generating a chaotic sequence by a hyperchaotic Chen system, and performing ring rotation twice on a plaintext image to realize efficient global scrambling; then, a one-dimensional chaotic system 1DL-SCS is used to perform line-by-line index scrambling on the image, and then the pixel points are redistributed column by column to further break the correlation between the pixels; in the diffusion stage, the plaintext is divided into four parts, substituted into an improved generalized Feistel cipher structure for calculation, and further divided into two parts in the round function, so that the diffusion efficiency is greatly improved, and through two rounds of iteration operation, a good encryption effect can be obtained, and the security is high.

Description

Technical Field

[0001] This invention relates to the field of image encryption technology, and more particularly to an image encryption method based on circular rotation and a generalized Feistel cryptographic structure. Background Technology

[0002] In the era of big data, images, as a common carrier of information, can cause unpredictable consequences if stolen or leaked. Therefore, images are usually encrypted to ensure the security of image information. Due to the large amount of information, high redundancy, and high correlation between pixels in images, many algorithms suitable for text encryption are not suitable for image encryption.

[0003] Chaotic systems possess excellent properties such as pseudo-randomness, unpredictability, and high sensitivity to initial values ​​and parameters, and have been widely used in image encryption in recent years. Existing one-dimensional chaotic systems are widely used due to their simple structure and short iteration time, but most suffer from the drawback of a small range of parameter values. Furthermore, existing image scrambling and diffusion methods also have some inherent limitations, such as the periodicity of the Arnold map, the fact that traditional Zigzag scrambling is only applicable to square matrices, and the low security of traditional three-term XOR diffusion methods.

[0004] Therefore, there is an urgent need to provide an image encryption method based on circular rotation and a generalized Feistel cryptographic structure. Summary of the Invention

[0005] To address the shortcomings of using only chaotic systems, image scrambling, and diffusion methods for image encryption, this paper proposes an image encryption method based on circular rotation and a generalized Feistel cryptographic structure. The method involves performing two circular rotations on the plaintext image using a chaotic sequence generated by a hyperchaotic Chen system, achieving efficient global scrambling. Then, a one-dimensional chaotic system, 1DL-SCS, is used to perform row-by-row indexing scrambling, followed by column-by-column pixel redistribution to further break the correlation between pixels. In the diffusion stage, the plaintext is divided into four parts, which are then substituted into the improved generalized Feistel cryptographic structure for calculation. The plaintext is further divided into two parts in the round function, significantly improving diffusion efficiency. Through two rounds of iterative computation, a good encryption effect can be achieved.

[0006] The technical means employed in this invention are as follows:

[0007] This invention provides an image encryption method based on circular rotation and a generalized Feistel cryptographic structure, comprising:

[0008] Input the original image;

[0009] The original image is processed using a hash algorithm to obtain a key, a subkey is obtained based on the key, and initial values ​​and parameters are calculated based on the subkey. The initial values ​​include a first initial value, a first initial value group, and a second initial value group. The parameters include a first control parameter, a second control parameter, a third control parameter, and a fourth control parameter.

[0010] The first initial value group and the first control parameters are substituted into the hyperchaotic Chen system for iteration to obtain the first chaotic sequence group. The original image is then subjected to circular rotation and recombination processing based on the first chaotic sequence group to obtain the primary image.

[0011] The first initial value, the third control parameter, and the fourth control parameter are substituted into the 1DL-SCS system and iterated to obtain the chaos matrix;

[0012] The intermediate image is obtained by indexing and scrambling the primary image according to the chaotic matrix.

[0013] The intermediate image is converted into a one-dimensional sequence, and the one-dimensional sequence is decomposed into four first sub-sequences;

[0014] Substitute the second initial value group and the second control parameters into the hyperchaotic Chen system for iteration to obtain the second chaotic sequence group, and process the second chaotic sequence group to generate the round key;

[0015] Four second subsequences are obtained by iterating through the four first subsequences according to the round key;

[0016] The four second subsequences are converted into matrices and then concatenated to obtain the ciphertext image.

[0017] Further, the step of processing the original image using a hash algorithm to obtain a key, and obtaining a subkey based on the key, includes:

[0018] The original image is processed using a hash algorithm to obtain 512 bits of binary data, and the first 450 bits of the binary data are taken as the key.

[0019] Starting from the first bit of the key, extract a group of sub-data every 30 bits to obtain the first to the 15th sub-data in sequence;

[0020] The first to fifteenth subkeys are obtained based on the first to fifteenth subdata, and are calculated according to the following formula:

[0021]

[0022] Where, k i Let be the i-th subkey, bi2de be the operation to convert a binary number to a decimal number, and k′ be the subkey.i Let i be the i-th sub-data, and j be the j-th bit.

[0023] Further, the initial value and parameters are calculated based on the subkey according to the following formula:

[0024]

[0025] Where x0 is the first initial value, x1, y1, z1, and w1 constitute the first initial value group, x2, y2, z2, and w2 constitute the second initial value group, r1 is the first control parameter, r2 is the second control parameter, λ is the third control parameter, μ is the fourth control parameter, and mod is the modulo operation.

[0026] Further, the step of substituting the first initial value set and the first control parameters into the hyperchaotic Chen system for iteration to obtain the first chaotic sequence set includes:

[0027] Calculate a specific value based on the original image;

[0028] Substitute the first initial value group and the first control parameter into the hyperchaotic Chen system and iterate L / 2+1000 times, where L is the specific value. Discard the first 1000 values ​​to obtain the first chaotic sequence group, which includes the first chaotic sequence to the fourth chaotic sequence.

[0029] Further, the step of performing circular rotation and recombination processing on the original image based on the first chaotic sequence group to obtain the primary image includes:

[0030] The first to fourth chaotic sequences are processed respectively to obtain the first to fourth processing results, which are calculated according to the following formula:

[0031] R a =mod(floor(R′) a × 10 10 ), 256);

[0032] Among them, R′ a Let be the a-th chaotic sequence, mod be the modulo operation, and floor be the floor number not exceeding (R′). a ×10 10 Operations on the largest integer in R a This is the result of processing number a;

[0033] The original image is divided into m×m arrayed first image blocks. The first moving direction and the first moving distance are determined according to the first processing result and the second processing result. The first image block of the b-th circle is rotated in a ring according to the first moving direction and the first moving distance to obtain the first image.

[0034] The first image is divided into two image blocks arranged in a 2×2 array, and the positions of two second image blocks with opposite apical corners are swapped to obtain the second image.

[0035] The second image is divided into m×m arrayed third image blocks. The second moving direction and the second moving distance are determined according to the third processing result and the fourth processing result. The third image blocks of the cth circle are rotated in a ring according to the second moving direction and the second moving distance to obtain the primary image.

[0036] Further, the step of substituting the first initial value, the third control parameter, and the fourth control parameter into the 1DL-SCS system for iteration to obtain the chaotic matrix includes:

[0037] The first initial value, the third control parameter, and the fourth control parameter are substituted into the 1DL-SCS system and iterated M×N+1000 times. The first 1000 values ​​are discarded to generate the chaotic matrix of size M×N.

[0038] Further, the step of substituting the second initial value set and the second control parameters into the hyperchaotic Chen system for iteration to obtain a second chaotic sequence set, and processing the second chaotic sequence set to generate a round key, includes:

[0039] Substitute the second initial value group and the second control parameter into the hyperchaotic Chen system and iterate (M×N) / 4+1000 times, discarding the first 1000 values ​​to generate the second chaotic sequence group, which includes the first chaotic subsequence to the fourth chaotic subsequence.

[0040] The round key is obtained from the first chaotic subsequence to the fourth chaotic subsequence, and is calculated according to the following formula:

[0041]

[0042] Where mod is the modulo operation, T1 is the first chaotic subsequence, T2 is the second chaotic subsequence, T3 is the third chaotic subsequence, T4 is the fourth chaotic subsequence, and abs is the absolute value operation.

[0043] Further, the four first subsequences are iterated over according to the round key to obtain four second subsequences, which are then calculated according to the following formula:

[0044]

[0045] Where r is the iteration number, r = 0 or r = 1. When r = 1, A r+1 B r+1 C r+1 D r+1 For the four second subsequences, F is the operation of the F(P, K) function.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] 1. The image encryption method based on ring rotation and generalized Feistel cryptography provided by this invention increases the parameter space of chaotic states by using a one-dimensional chaotic system 1DL-SCS with two control parameters, which can produce more complex chaotic behavior and has better chaotic characteristics.

[0048] 2. The image encryption method based on circular rotation and generalized Feistel cryptography provided by this invention performs two circular rotations on the plaintext image using a chaotic sequence generated by the hyperchaotic Chen system, achieving efficient global scrambling. Then, the image is indexed and scrambled row by row using the one-dimensional chaotic system 1DL-SCS, followed by column-by-column redistribution of pixels to further break the correlation between pixels. In the diffusion stage, the plaintext is divided into four parts, which are then substituted into the improved generalized Feistel cryptography for calculation, and further divided into two parts in the round function, greatly improving the diffusion efficiency. Through two rounds of iterative calculation, a good encryption effect can be obtained with high security. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a flowchart of an image encryption method based on circular rotation and a generalized Feistel cryptographic structure provided by the present invention.

[0051] Figure 2 This is a schematic diagram of a generalized Feistel encryption structure.

[0052] Figure 3 This is the original image.

[0053] Figure 4 for Figure 3A first image after the first circular rotation scrambling.

[0054] Figure 5 for Figure 4 A second image resulting from block recombination.

[0055] Figure 6 for Figure 5 A primary image after the second circular rotation scramble.

[0056] Figure 7 This is a schematic diagram of one-dimensional sequence decomposition. Detailed Implementation

[0057] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0058] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention 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 the invention 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 a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0059] Combination Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 , Figure 1 This is a flowchart of an image encryption method based on circular rotation and a generalized Feistel cryptographic structure provided by the present invention. Figure 2 This is a schematic diagram of a generalized Feistel encryption structure. Figure 3 For the original image, Figure 4 for Figure 3 A first image after the first circular rotation scrambling. Figure 5 for Figure 4A second image resulting from block recombination Figure 6 for Figure 5 A preliminary image after the second circular rotation scrambling. Figure 7 This is a schematic diagram of one-dimensional sequence decomposition, illustrating a specific embodiment of the image encryption method based on circular rotation and generalized Feistel cryptography provided by the present invention, including:

[0060] Input the original image;

[0061] The original image is processed using a hash algorithm to obtain a key. A subkey is obtained based on the key. Initial values ​​and parameters are then calculated based on the subkey. The initial values ​​include a first initial value, a first initial value group, and a second initial value group. The parameters include a first control parameter, a second control parameter, a third control parameter, and a fourth control parameter.

[0062] The original image serves as the data source. The SHA-512 hash algorithm processes the data source to obtain a key. Specifically, the original image is processed using a hash algorithm to obtain a key, and a subkey is derived from this key, including:

[0063] The original image is processed using a hash algorithm to obtain 512 bits of binary data, and the first 450 bits of the binary data are used as the key.

[0064] Starting from the first bit of the key, extract a group of sub-data every 30 bits to obtain the first to the 15th sub-data in sequence;

[0065] The first to fifteenth subkeys are obtained based on the corresponding subdata, and then calculated according to the following formula:

[0066]

[0067] Where, k i Let be the i-th subkey, bi2de be the operation to convert a binary number to a decimal number, and k′ be the subkey. i Let i be the i-th sub-data, and j be the j-th bit.

[0068] Calculate the initial value and parameters based on the subkey, using the following formula:

[0069]

[0070] Where x0 is the first initial value, x1, y1, z1, and w1 constitute the first initial value group, x2, y2, z2, and w2 constitute the second initial value group, r1 is the first control parameter, r2 is the second control parameter, λ is the third control parameter, μ is the fourth control parameter, and mod is the modulo operation.

[0071] The first initial value set and the first control parameters are substituted into the hyperchaotic Chen system for iteration to obtain the first chaotic sequence set. The original image is then subjected to circular rotation and recombination based on the first chaotic sequence set to obtain the primary image.

[0072] Specifically, the first set of initial values ​​and the first set of control parameters are substituted into the hyperchaotic Chen system for iteration to obtain the first set of chaotic sequences, including:

[0073] Calculate specific values ​​based on the original image;

[0074] Substitute the first initial value set and the first control parameter into the hyperchaotic Chen system and iterate L / 2+1000 times, where L is a specific value. Discard the first 1000 values ​​to obtain the first chaotic sequence set, which includes the first chaotic sequence to the fourth chaotic sequence.

[0075] It is understandable that the original image has dimensions E×F, and specific values ​​are set according to the following formula:

[0076] L = min(E, F);

[0077] Further, the original image is subjected to circular rotation and recombination based on the first chaotic sequence group to obtain a primary image, including:

[0078] The chaotic sequences 1 through 4 are processed respectively to obtain the processing results 1 through 4, which are then calculated according to the following formula:

[0079] R a =mod(floor(R′) a ×10 10 ), 256);

[0080] Among them, R′ a Let be the a-th chaotic sequence, mod be the modulo operation, and floor be the floor number not exceeding (R′). a ×10 10 Operations on the largest integer in R a For the result of processing the a-th time, a = {1, 2, 3, 4};

[0081] The original image is divided into m×m arrayed first image blocks. The first moving direction and the first moving distance are determined according to the first processing result and the second processing result. The first image blocks of the b-th circle are rotated in a ring according to the first moving direction and the first moving distance to obtain the first image.

[0082] Where 1≤b≤L / 2, refer to Figure 3 and Figure 4The first processing result is R1, and the second processing result is R2. When R1 > R2, the first image block of the b-th cycle moves clockwise by R1 positions; when R1 ≤ R2, the first image block of the b-th cycle moves counterclockwise by R2 positions.

[0083] The first image is divided into two image blocks arranged in a 2×2 array. The positions of two image blocks with opposite vertices are swapped to obtain the second image.

[0084] Among them, reference Figure 4 and Figure 5 There are four second image blocks, located at the top left, top right, bottom left, and bottom right corners of the first image. The second image is obtained by swapping the positions of the two second image blocks that are opposite each other at the top corners. Specifically, the positions of the second image blocks at the top left and bottom right corners are swapped, and the positions of the second image blocks at the top right and bottom left corners are swapped.

[0085] The second image is divided into m×m arrays of third image blocks. The second moving direction and the second moving distance are determined based on the third and fourth processing results. The third image blocks of the cth ring are rotated in a ring according to the second moving direction and the second moving distance to obtain the primary image.

[0086] Where 1≤c≤L / 2, refer to Figure 5 and Figure 6 The third processing result is R3, and the fourth processing result is R4. When R3 > R4, the third image block of the c-th cycle moves clockwise by R3 positions; when R3 ≤ R4, the third image block of the c-th cycle moves counterclockwise by R4 positions.

[0087] Substituting the first initial value, the third control parameter, and the fourth control parameter into the 1DL-SCS system and iterating, the chaos matrix is ​​obtained.

[0088] Substituting the first initial value, the third control parameter, and the fourth control parameter into the 1DL-SCS system and iterating, the chaotic matrix is ​​obtained, including:

[0089] Substitute the first initial value, the third control parameter, and the fourth control parameter into the 1DL-SCS system and iterate M×N+1000 times, discarding the first 1000 values ​​to generate a chaotic matrix of size M×N.

[0090] The intermediate image is obtained by indexing and scrambling the primary image based on the chaotic matrix.

[0091] The intermediate image is transformed into a one-dimensional sequence, and the one-dimensional sequence is decomposed into four first subsequences;

[0092] Specifically, refer to Figure 7The one-dimensional sequence consists of 12 digits, which are sequentially assigned to the four first subsequences starting from the first digit, resulting in A0: 46, 36, 16; B0: 13, 4, 49; C0: 27, 18, 7; and D0: 21, 33, 35.

[0093] Substitute the second initial value set and the second control parameters into the hyperchaotic Chen system for iteration to obtain the second chaotic sequence set, and process the second chaotic sequence set to generate the round key;

[0094] Specifically, the second initial value set and the second control parameters are substituted into the hyperchaotic Chen system for iteration to obtain the second chaotic sequence set. The second chaotic sequence set is then processed to generate the round key, including:

[0095] Substitute the second initial value set and the second control parameters into the hyperchaotic Chen system and iterate (M×N) / 4+1000 times, discarding the first 1000 values ​​to generate the second chaotic sequence set, which includes the first chaotic subsequence to the fourth chaotic subsequence.

[0096] The round key is obtained from the first to the fourth chaotic subsequences and is calculated using the following formula:

[0097]

[0098] Where mod is the modulo operation, T1 is the first chaotic subsequence, T2 is the second chaotic subsequence, T3 is the third chaotic subsequence, T4 is the fourth chaotic subsequence, and abs is the absolute value operation.

[0099] Four second subsequences are obtained by iterating through the four first subsequences based on the round key;

[0100] Specifically, refer to Figure 2 Four second subsequences are obtained by iterating through the four first subsequences based on the round key, and then calculated according to the following formula:

[0101]

[0102] Where r is the iteration number, r = 0 or r = 1. When r = 1, A r+1 B r+1 C r+1 D r+1 There are 4 second subsequences, and F is the operation of the F(P, K) function.

[0103] In the function F(P, K), P is a one-dimensional sequence, and K is the round key, including... and The function F(P, K) outputs a value of Q, where P, K, and Q are all of equal length, each being D. Q is calculated using the following formula:

[0104]

[0105]

[0106]

[0107] Where q is the q-th position of the one-dimensional sequence.

[0108] The ciphertext image is obtained by concatenating the four second subsequences into matrices.

[0109] Specifically, A2, B2, C2, and D2 are converted into matrices of size (E / 2) × (F / 2). The matrix corresponding to A2 is used as the upper left part, the matrix corresponding to B2 as the upper right part, the matrix corresponding to C2 as the lower left part, and the matrix corresponding to D2 as the lower right part. These matrices are then concatenated to form the ciphertext image, thus completing the encryption.

[0110] Simulation experiments, statistical analysis, key analysis, robustness analysis, and differential attack tests demonstrate that the image encryption method based on ring rotation and generalized Feistel cryptographic structure provided in this invention has good ciphertext statistical properties and strong resistance to various attacks, with higher security than most existing image encryption schemes.

[0111] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0112] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An image encryption method based on circular rotation and a generalized Feistel cryptographic structure, characterized in that, include: Input the original image; The original image is processed using a hash algorithm to obtain a key, a subkey is obtained based on the key, and initial values ​​and parameters are calculated based on the subkey. The initial values ​​include a first initial value, a first initial value group, and a second initial value group. The parameters include a first control parameter, a second control parameter, a third control parameter, and a fourth control parameter. Substituting the first initial value set and the first control parameters into the hyperchaotic Chen system for iteration yields a first chaotic sequence set. Based on the first chaotic sequence set, the original image is subjected to circular rotation and recombination processing to obtain a primary image, including: The chaotic sequences 1 through 4 are processed respectively to obtain the processing results 1 through 4, which are then calculated according to the following formula: ； in, For the first Chaotic sequence, For the modulo operation, To take no more than Operations on the largest integer, For the first Processing results; The original image is divided into m×m arrayed first image blocks. The first moving direction and the first moving distance are determined according to the first processing result and the second processing result. The first image block of the b-th circle is rotated in a ring according to the first moving direction and the first moving distance to obtain the first image. The first image is divided into two image blocks arranged in a 2×2 array, and the positions of two second image blocks with opposite apical corners are swapped to obtain the second image. The second image is divided into m×m arrayed third image blocks. The second moving direction and the second moving distance are determined according to the third processing result and the fourth processing result. The third image blocks of the cth circle are rotated in a ring according to the second moving direction and the second moving distance to obtain the primary image. The first initial value, the third control parameter, and the fourth control parameter are substituted into the 1DL-SCS system and iterated to obtain the chaos matrix; The intermediate image is obtained by indexing and scrambling the primary image according to the chaotic matrix. The intermediate image is converted into a one-dimensional sequence, and the one-dimensional sequence is decomposed into four first sub-sequences; Substitute the second initial value group and the second control parameters into the hyperchaotic Chen system for iteration to obtain the second chaotic sequence group, and process the second chaotic sequence group to generate the round key; Four second subsequences are obtained by iterating through the four first subsequences according to the round key; The four second subsequences are converted into matrices and then concatenated to obtain the ciphertext image.

2. The image encryption method based on circular rotation and generalized Feistel cryptography according to claim 1, characterized in that, The process of processing the original image using a hash algorithm to obtain a key, and then obtaining a subkey based on the key, includes: The original image is processed using a hash algorithm to obtain 512 bits of binary data, and the first 450 bits of the binary data are taken as the key. Starting from the first bit of the key, extract a group of sub-data every 30 bits to obtain the first to the 15th sub-data in sequence; The first to fifteenth subkeys are obtained based on the first to fifteenth subdata, and are calculated according to the following formula: ； in, For the first Subkey, Operations to convert binary numbers to decimal numbers, For the first Sub-data, For the first 1 bit.

3. The image encryption method based on circular rotation and generalized Feistel cryptography according to claim 2, characterized in that, The initial value and parameters are calculated based on the subkey according to the following formula: ； in, The first initial value, , , , This constitutes the first initial value group. , , , This constitutes the second set of initial values. The first control parameter is... This is the second control parameter. The third control parameter, The fourth control parameter, This is the modulo operation.

4. The image encryption method based on circular rotation and generalized Feistel cryptography according to claim 1, characterized in that, The step of substituting the first initial value set and the first control parameters into the hyperchaotic Chen system for iteration to obtain the first chaotic sequence set includes: Calculate a specific value based on the original image; Substitute the first initial value group and the first control parameter into the hyperchaotic Chen system and iterate L / 2+1000 times, where L is the specific value. Discard the first 1000 values ​​to obtain the first chaotic sequence group, which includes the first chaotic sequence to the fourth chaotic sequence.

5. The image encryption method based on circular rotation and generalized Feistel cryptography according to claim 1, characterized in that, The step of substituting the first initial value, the third control parameter, and the fourth control parameter into the 1DL-SCS system for iteration to obtain the chaotic matrix includes: The first initial value, the third control parameter, and the fourth control parameter are substituted into the 1DL-SCS system and iterated M×N+1000 times. The first 1000 values ​​are discarded to generate the chaotic matrix of size M×N.

6. The image encryption method based on circular rotation and generalized Feistel cryptography according to claim 5, characterized in that, The step of substituting the second initial value set and the second control parameters into the hyperchaotic Chen system for iteration to obtain the second chaotic sequence set, and processing the second chaotic sequence set to generate the round key, includes: Substitute the second initial value group and the second control parameter into the hyperchaotic Chen system and iterate (M×N) / 4+1000 times, discarding the first 1000 values ​​to generate the second chaotic sequence group, which includes the first chaotic subsequence to the fourth chaotic subsequence. The round key is obtained from the first to the fourth chaotic subsequences and calculated according to the following formula: ； in, For the modulo operation, For the first chaotic subsequence, This is the second chaotic subsequence. This is the 3rd chaotic subsequence. For the fourth chaotic subsequence, This is for absolute value operations.

7. The image encryption method based on circular rotation and generalized Feistel cryptography according to claim 5, characterized in that, The four first subsequences are iterated over according to the round key to obtain four second subsequences, which are then calculated according to the following formula: ； in, For the number of iterations, =0 or =1, when When =1, , , , For the four second subsequences, for Function operations.

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