Image encryption method based on new non-adjacent dynamic coupling mapping lattice and cross scrambling

Abstract

The invention discloses an image encryption method based on a new non-adjacent dynamic coupling mapping lattice and cross scrambling. The method comprises the following steps: acquiring an image to be processed; preprocessing an image to be processed to obtain parameters and initial values required by an encryption process; generating a chaotic sequence based on the parameters and the initial value required by the encryption process; adopting a cross traversal algorithm, selecting different central points and traversal directions of the image to perform preliminary scrambling on positions of image pixels, and obtaining an initial scrambling image; a random cross transformation algorithm is adopted to perform scrambling and diffusion operation based on the initial scrambling image, the pixel position of the image is changed, the pixel value of the image is preliminarily changed, and a semi-encrypted image is obtained; and carrying out secondary diffusion on the semi-encrypted image by adopting a bidirectional disturbance index diffusion algorithm to obtain an encrypted image. According to the method, corresponding attacks can be effectively resisted, and good safety is achieved; and the time efficiency is relatively high.

Description

Technical Field

[0001] The invention belongs to the technical field of image processing, and relates to an image encryption method based on a new non-adjacent dynamic coupling mapping grid and cross scrambling. Background Art

[0002] In this information age dominated by short videos, the rapid development of information technology has brought unprecedented convenience to people and made data sharing possible. As an important information medium, digital images are widely adopted due to their intuitiveness and simplicity, and play a vital role in many fields such as social media, healthcare, and national defense security. However, along with these advantages, the importance of image security has also become increasingly prominent. In order to ensure the security of images during transmission and prevent information from being stolen by unauthorized third parties, encrypting images has become a common and necessary practice. This not only protects the confidentiality of image content, but also provides a solid line of defense for information security, ensuring that personal privacy and sensitive information are not stolen and abused by criminals. In recent years, image encryption algorithms based on various technologies have been proposed. Although many image encryption methods have been developed, some of them are weak in security. Existing image encryption algorithms usually have problems such as high computational complexity, poor noise resistance, low encryption efficiency, complex key management, and insufficient security.

[0003] The classic spatiotemporal chaotic model Coupled Map Lattice (CML) is widely used in image encryption by arranging image pixels on a spatial grid and using chaotic iteration to achieve highly complex encryption effects. CML has the advantages of high security, rich adjustable parameters and strong spatial structure, and can resist a variety of attacks. However, CML is computationally complex and sensitive to noise and parameters, and needs to be optimized to achieve more efficient and secure applications.

[0004] The row and column scrambling algorithm is a commonly used image encryption method that implements encryption by changing the row and column positions of image pixels. Its advantages are simple structure, easy implementation, and can effectively hide the spatial distribution characteristics of the image and resist simple statistical analysis. However, its security is relatively low, the key space is limited, it is easy to be attacked to restore the image, and its anti-attack ability is insufficient when used alone. It usually needs to be used in combination with other algorithms to improve overall security. Summary of the invention

[0005] In order to solve the above problems, the technical solution adopted by the present invention is: an image encryption method based on a new non-adjacent dynamic coupling mapping grid and cross scrambling, comprising the following steps:

[0006] Obtain the image to be processed;

[0007] Preprocess the image to be processed to obtain the parameters and initial values ​​required for the encryption process;

[0008] Generate a chaotic sequence based on the parameters and initial values ​​required for the encryption process;

[0009] Using the cross traversal algorithm, different center points and traversal directions of the image are selected to preliminarily scramble the positions of the image pixels to obtain the initial disturbed image;

[0010] The random cross transformation algorithm is used to perform scrambling and diffusion operations based on the initial disturbed image, change the pixel position of the image, and preliminarily change the pixel value of the image to obtain a semi-encrypted image;

[0011] The bidirectional perturbation index diffusion algorithm is used to perform secondary diffusion on the semi-encrypted image to obtain the encrypted image.

[0012] Furthermore: the image is an image with pixels between 0-255.

[0013] Furthermore, the process of processing the image to be processed and obtaining the parameters and initial values ​​required for the encryption process adopts the SHA-512 algorithm.

[0014] Further: the parameters and initial values ​​required for the encryption process are used to generate a chaotic sequence, and the parameters and initial values ​​are used to iterate the sine-exponential non-adjacent dynamic coupling mapping lattice system respectively to obtain a chaotic sequence with a length of M×N, where M and N represent the length and width of the plaintext image respectively; the specific formula of the sine-exponential non-adjacent dynamic coupling mapping lattice system is as follows:

[0015]

[0016] Where: e is the coupling coefficient 0≤e≤1, the value range of control parameters μ, e and d is (0,+∞), n (n=1,2,3...) is the time series, i, j and k represent the spatial positions of three non-adjacent grids, p and q are the control parameters of Arnold mapping, and L represents the number of grids.

[0017] Further: the process of using the cross traversal algorithm to select different center points and traversal directions of the image to preliminarily scramble the positions of the image pixels to obtain the initial disturbed image is as follows:

[0018] S41: intercept some subsequences of the chaotic sequence A1, and sort them respectively to obtain the row index sequence R and column index sequence C of the plaintext image P. The specific formula is as follows:

[0019]

[0020] Where M and N represent the length and width of the plaintext image respectively.

[0021] S42: Mark the top of the center point as 1, the right as 2, the bottom as 3, and the left as 4 to determine the starting direction S;

[0022] The specific formula is as follows:

[0023] S=mod(floor(A1(2L+1:3L)×2 14 ),4)+1

[0024] S43: Determine the center points P(R(i), C(i)) at different positions according to the row index R and the column index C, take each center point as the starting point, and traverse all the untraversed pixels in the row and column where the center point is located clockwise according to the corresponding starting direction S, and put them into the one-dimensional sequence P1 in sequence, repeat S41-S43 until all pixels are traversed, and then rearrange the one-dimensional sequence P1 in column priority order to adjust its size to M×N, so as to obtain the initial disturbed image P1.

[0025] Further: the random cross transformation algorithm is used to perform scrambling and diffusion operations based on the initial disturbed image, change the pixel position of the image, and preliminarily change the pixel value of the image to obtain the semi-encrypted image. The process is as follows:

[0026] S51: again intercepting some subsequences of the chaotic sequence A1 and sorting them respectively to obtain different row index sequences AR and column index sequences AC. The specific formula is as follows:

[0027]

[0028] S52: According to the following formula, two integer sequences E1 and E2 are obtained for subsequent scrambling operations. At the same time, the chaotic sequences A2 and A3 are processed to obtain two matrices F1 and F2 of size M×N for subsequent diffusion operations. The specific formula is as follows:

[0029]

[0030]

[0031] S53: In each random cross-transformation cycle operation, a row of the image P1 is randomly selected using the row index sequence AR, and two different pixel positions on the row are randomly selected using the integer sequence E1, and then a scrambling operation is performed on the row and column of the selected position, and then a diffusion operation is performed in combination with F1 until the row index sequence AR is completed; similarly, a column of the image P1 is randomly selected using AC, and two different pixel positions on the column are randomly selected using the integer sequence E2, and then a scrambling operation is performed on the row and column of the selected position, and then a diffusion operation is performed in combination with F2 until the column index sequence AC is completed; in addition, a special scrambling process is performed on the outermost rows and columns of the image P1, in which the row is cyclically moved one position to the right and the column is cyclically moved one position downward to obtain a semi-encrypted image P2.

[0032] Furthermore, the process of using the bidirectional perturbation index diffusion algorithm to perform secondary diffusion on the semi-encrypted image to obtain the encrypted image is as follows:

[0033] S61: First, the chaotic sequence A4 is sorted in ascending order to obtain a global index sequence IA of the image P2. The specific formula is as follows:

[0034] [~,IA]=sort(A4)

[0035] S62: Use the chaotic sequence A5 to quickly perturb IA through a quick sorting algorithm to obtain a forward index sequence IB. The forward index sequence IB can be used to generate a backward index sequence IC. The specific formula is as follows:

[0036] IC=flip(IB)

[0037] S63: Convert the semi-encrypted image P2 into a one-dimensional sequence p. First, diffuse p using the forward index sequence IB to obtain a one-dimensional sequence c1. Then diffuse c1 using the backward index sequence IC to obtain a one-dimensional sequence c2. The specific formula is as follows:

[0038]

[0039]

[0040] S64: Adjust the one-dimensional sequence c2 to an M×N matrix to obtain the final encrypted image C.

[0041] An image encryption device based on a new non-adjacent dynamic coupling mapping grid and cross scrambling, comprising:

[0042] Acquisition module: used to acquire the image to be processed;

[0043] Preprocessing module: used to preprocess the image to be processed to obtain the parameters and initial values ​​required for the encryption process;

[0044] Generation module: used to generate chaotic sequences based on the parameters and initial values ​​required by the encryption process;

[0045] Initial disturbance module: used to use the cross traversal algorithm to select different center points and traversal directions of the image to perform preliminary scrambling on the positions of the image pixels to obtain the initial disturbed image;

[0046] Semi-encrypted module: used to perform scrambling and diffusion operations based on the initial disturbed image using a random cross transformation algorithm, change the pixel position of the image, and preliminarily change the pixel value of the image to obtain a semi-encrypted image;

[0047] Secondary diffusion module: used to perform secondary diffusion on the semi-encrypted image using a bidirectional perturbation index diffusion algorithm to obtain an encrypted image.

[0048] A computer device comprises: a processor and a memory, wherein the memory stores a program module, and wherein the program module runs on the processor to implement the method according to any one of claims 1 to 7.

[0049] The present invention provides an image encryption method based on a novel non-adjacent dynamic coupling mapping grid and cross scrambling, which has the following advantages:

[0050] 1. A new sine-exponential non-adjacent dynamical coupled mapping lattice (SENDCML) is proposed. Compared with other spatiotemporal chaotic models, SENDCML has a larger parameter range and better chaotic performance.

[0051] 2. A cross traversal algorithm is proposed, which can flexibly select different center points and traversal directions to perform preliminary scrambling of the positions of image pixels. It is completely different from other scrambling algorithms.

[0052] 3. A new row-column random cross-transformation algorithm is proposed, which can perform scrambling and diffusion operations simultaneously, ensuring the adequacy of image scrambling and the initial diffusion effect, and improving the security and speed of encryption.

[0053] 4. A quick sorting algorithm is used to quickly disrupt the index sequence, and a bidirectional disrupted index diffusion algorithm is proposed, which can perform secondary diffusion on the image, ensuring the adequacy of image diffusion and improving the encryption effect.

[0054] Using the method of this application to encrypt an image, we can obtain an image that is completely consistent with the image before encryption through the decryption method. We have conducted detailed tests on the encrypted and decrypted ciphertext images, as well as the original images and decrypted images, proving that the key space of the encryption key is large enough and the key is very sensitive; we have conducted detailed tests on the histogram of the encrypted image, correlation analysis in three directions, chi-square test, information entropy analysis, pixel difference analysis, NPCR and UACI test analysis, etc., and found that it has a good encryption effect; we have conducted relevant robustness analysis on our algorithm, including salt and pepper attacks and different degrees of cropping attacks, and we found that our method can effectively resist the corresponding attacks and has good security; we have conducted a time complexity analysis on our method and found that our method has high time efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0056] Figure 1 Flowchart of the method of this application

[0057] Figure 2 It is the encryption flow chart;

[0058] Figure 3 is a cross traversal graph;

[0059] Figure 4 is a random crossover transformation graph;

[0060] Figure 5 is a fast scrambled graph of the index sequence. DETAILED DESCRIPTION

[0061] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0062] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] Figure 1 is a flow chart of the method;

[0064] An image encryption method based on a new non-adjacent dynamic coupling mapping grid and cross scrambling includes the following steps:

[0065] S1: Obtain the image to be processed;

[0066] S2: preprocessing the image to be processed to obtain the parameters and initial values ​​required for the encryption process;

[0067] S3: Generate a chaotic sequence based on the parameters and initial values ​​required for the encryption process;

[0068] S4: using a cross traversal algorithm, selecting different center points and traversal directions of the image to preliminarily scramble the positions of the image pixels to obtain an initial disturbed image;

[0069] S5: using a random cross transformation algorithm to perform scrambling and diffusion operations based on the initial disturbed image, changing the pixel position of the image, and preliminarily changing the pixel value of the image to obtain a semi-encrypted image;

[0070] S6: Using a bidirectional perturbation index diffusion algorithm, the semi-encrypted image is diffused twice to obtain an encrypted image.

[0071] Steps S1 / S2 / S3 / S4 / S5 / S6 are executed in sequence;

[0072] The image is an image with pixels between 0-255.

[0073] Figure 2 It is the encryption flow chart;

[0074] The process of preprocessing the image to be processed and obtaining the parameters and initial values ​​required for the encryption process adopts the SHA-512 algorithm, and the specific process is as follows:

[0075] Key generation: Use the plaintext image P as the input of the SHA-512 algorithm to generate a 512-bit binary number, and select 400 bits as the key K. Divide the key K into 10 groups k1-k 10 , each group is 40 bits. 10 The control parameters e, μ, d and initial values ​​x1-x6 of the sine-exponential non-adjacent dynamic coupling mapping lattice (SENDCML) are obtained. The specific formula of SENDCML is as follows:

[0076]

[0077] Where: e is the coupling coefficient 0≤e≤1, the range of control parameters μ, e and d is (0, +∞), n (n=1,2,3...) is the time series. i, j and k represent the spatial positions of three non-adjacent grids, p and q are the control parameters of Arnold mapping, and L represents the number of grids. The specific algorithm is as follows:

[0078] Input: K

[0079] for i=1:10

[0080] k i =K(40(i-1)+1:40(i-1)+40)

[0081] end

[0082]

[0083]

[0084]

[0085]

[0086]

[0087] for i=2:6

[0088]

[0089] end

[0090] Output: e,μ,d,x1,x2,x3,x4,x5,x6

[0091] Encryption process: According to the parameters e, μ, d and different initial values ​​x1-x6, the sine-exponential non-adjacent dynamic coupled mapping lattice (SENDCML) is iterated M×N+500 times, and the first 500 values ​​are discarded to eliminate transient effects. The chaotic sequences A1-A6 with a length of M×N are obtained for the encryption process, where M and N represent the length and width of the plaintext image, respectively.

[0092] Figure 3 is a cross traversal graph;

[0093] Further: the process of using the cross traversal algorithm to select different center points and traversal directions of the image to preliminarily scramble the positions of the image pixels, thereby preliminarily disturbing the pixel positions of the plaintext image and obtaining the initial disturbed image is as follows:

[0094] S41: intercept some subsequences of the chaotic sequence A1, and sort them respectively to obtain the row index sequence R and column index sequence C of the plaintext image P. The specific formula is as follows:

[0095]

[0096] Where M and N represent the length and width of the plaintext image respectively.

[0097] S42: Mark the top of the center point as 1, the right as 2, the bottom as 3, and the left as 4 to determine the starting direction S;

[0098] The specific formula is as follows:

[0099] S=mod(floor(A1(2L+1:3L)×2 14 ),4)+1

[0100] S43: Determine the center points P(R(i), C(i)) at different positions according to the row index R and the column index C, take each center point as the starting point, and traverse all the untraversed pixels in the row and column where the center point is located clockwise according to the corresponding starting direction S, and put them into the one-dimensional sequence P1 in sequence, repeat S41-S43 until all pixels are traversed, and then rearrange the one-dimensional sequence P1 in column priority order to adjust its size to M×N, so as to obtain the initial disturbed image P1.

[0101] The pseudo code of the cross traversal algorithm is as follows:

[0102] Input: P,L,R,C,S

[0103] [M,N]=size(P)

[0104] P1=[]

[0105] for i=1:L

[0106] switch(S(i))

[0107] case 1:

[0108] P1=Traversal_1(P1,P(R(i),C(i))

[0109] case 2:

[0110] P1=Traversal_2(P1,P(R(i),C(i))

[0111] case 3:

[0112] P1=Traversal_3(P1,P(R(i),C(i))

[0113] case 4:

[0114] P1=Traversal_4(P1,P(R(i),C(i))

[0115] end

[0116] end

[0117] P1=reshape(P1,[M,N])

[0118] Output: P1

[0119] Figure 4 is a random crossover transformation graph;

[0120] Furthermore, the random cross transformation algorithm is used to perform scrambling and diffusion operations based on the initial disturbed image, change the pixel position of the image, and preliminarily change the pixel value of the image to obtain the semi-encrypted image. The process is as follows:

[0121] S51: again intercepting some subsequences of the chaotic sequence A1 and sorting them respectively to obtain different row index sequences AR and column index sequences AC. The specific formula is as follows:

[0122]

[0123] S52: According to the following formula, two integer sequences E1 and E2 are obtained for subsequent scrambling operations. At the same time, the chaotic sequences A2 and A3 are processed to obtain two matrices F1 and F2 of size M×N for subsequent diffusion operations. The specific formula is as follows:

[0124]

[0125]

[0126] S53: In each random cross-transformation cycle operation, a row of the image P1 is randomly selected using the row index sequence AR, and two different pixel positions on the row are randomly selected using the integer sequence E1, and then a scrambling operation is performed on the row and column of the selected position, and then a diffusion operation is performed in combination with F1 until the row index sequence AR is completed; similarly, a column of the image P1 is randomly selected using AC, and two different pixel positions on the column are randomly selected using the integer sequence E2, and then a scrambling operation is performed on the row and column of the selected position, and then a diffusion operation is performed in combination with F2 until the column index sequence AC is completed; in addition, a special scrambling process is performed on the outermost rows and columns of the image P1, in which the row is cyclically moved one position to the right and the column is cyclically moved one position downward to obtain a semi-encrypted image P2.

[0127] The pseudo code of the random crossover transformation algorithm is as follows:

[0128] Input: P1, L, AR, AC, E1, E2, F1, F2

[0129] [M,N]=size(P1)

[0130] ARS=flip(AR)

[0131] ACS=flip(AC)

[0132] k1=1

[0133] k2=1

[0134] for i=1:L

[0135] H1=E1(k1:k1+1)

[0136] for j=1:length(H1)

[0137] if AR(i)==1||AR(i)==M||H1(j)==1||H1(j)==N

[0138] P1(AR(i),:)=[P1(AR(i),end),P1(AR(i),1:end-1)];

[0139] P1(:,H1(j))=[P1(end,H1(j));P1(1:end-1,H1(j))];

[0140] else

[0141] P1(AR(i),:)=[P1(AR(i),H1(j):1:end),P1(AR(i),H1(j)-1:-1:1)];

[0142] P1(:,H1(j))=[P1(AR(i):1:end,H1(j));P1(AR(i)-1:-1:1,H1(j))];

[0143] end

[0144] P1(AR(i),:)=bitxor(P1(AR(i),:),F1(ARS(i),:));

[0145] P1(:,H1(j))=bitxor(P1(:,H1(j)),F1(:,H1(j)));

[0146] end

[0147] k1=k1+2

[0148] H2=E2(k2:k2+1)

[0149] for j=1:length(H2)

[0150] if AC(i)==1||AC(i)==N||H2(j)==1||H2(j)==M

[0151] P1(:,AC(i))=[P1(end,AC(i));P1(1:end-1,AC(i))];

[0152] P1(H2(j),:)=[P1(H2(j),end),P1(H2(j),1:end-1)];

[0153] else

[0154] P1(:,AC(i))=[P1(H2(j):1:end,AC(i));P1(H2(j)-1:-1:1,AC(i))];

[0155] P1(H2(j),:)=[P1(H2(j),AC(i):1:end),P1(H2(j),AC(i)-1:-1:1)];

[0156] end

[0157] P1(:,AC(i))=bitxor(P1(:,AC(i)),F2(:,ACS(i)));

[0158] P1(H2(j),:)=bitxor(P1(H2(j),:),F2(H2(j),:));

[0159] end

[0160] k2=k2+2

[0161] end

[0162] P2=P1

[0163] Output: P2

[0164] Figure 5 is a fast scrambled graph of the index sequence;

[0165] Furthermore: the process of using the bidirectional perturbation index diffusion algorithm to perform secondary diffusion on the semi-encrypted image and further change the pixel value of the entire image to obtain the encrypted image is as follows:

[0166] S61: First, the chaotic sequence A4 is sorted in ascending order to obtain a global index sequence IA of the image P2. The specific formula is as follows:

[0167] [~,IA]=sort(A4)

[0168] S62: Use the chaotic sequence A5 to quickly perturb IA through a quick sorting algorithm to obtain a forward index sequence IB. The forward index sequence IB can be used to generate a backward index sequence IC. The specific formula is as follows:

[0169] IC=flip(IB)

[0170] S63: Convert the semi-encrypted image P2 into a one-dimensional sequence p. First, diffuse p using the forward index sequence IB to obtain a one-dimensional sequence c1. Then diffuse c1 using the backward index sequence IC to obtain a one-dimensional sequence c2. The specific formula is as follows:

[0171]

[0172]

[0173] S64: Adjust the one-dimensional sequence c2 to an M×N matrix to obtain the final encrypted image C.

[0174] The pseudo code of the index sequence fast scrambling algorithm is as follows:

[0175] Input: IA,A,left,right

[0176]

[0177] Output: IB

[0178] An image encryption device based on a new non-adjacent dynamic coupling mapping grid and cross scrambling, comprising:

[0179] Acquisition module: used to acquire the image to be processed;

[0180] Preprocessing module: used to preprocess the image to be processed to obtain the parameters and initial values ​​required for the encryption process;

[0181] Generation module: used to generate chaotic sequences based on the parameters and initial values ​​required by the encryption process;

[0182] Initial disturbance module: used to use the cross traversal algorithm to select different center points and traversal directions of the image to perform preliminary scrambling on the positions of the image pixels to obtain the initial disturbed image;

[0183] Semi-encrypted module: used to perform scrambling and diffusion operations based on the initial disturbed image using a random cross transformation algorithm, change the pixel position of the image, and preliminarily change the pixel value of the image to obtain a semi-encrypted image;

[0184] Secondary diffusion module: used to perform secondary diffusion on the semi-encrypted image using a bidirectional perturbation index diffusion algorithm to obtain an encrypted image.

[0185] A computer device comprises: a processor and a memory, wherein the memory stores a program module, and wherein the program module runs on the processor to implement any of the methods described above.

[0186] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 a new non-adjacent dynamic coupling mapping grid and cross scrambling, characterized by: The following steps are involved: Obtain the image to be processed; Preprocess the image to be processed to obtain the parameters and initial values ​​required for the encryption process; Generate a chaotic sequence based on the parameters and initial values ​​required for the encryption process; Using the cross traversal algorithm, different center points and traversal directions of the image are selected to preliminarily scramble the positions of the image pixels to obtain the initial disturbed image; The random cross transformation algorithm is used to perform scrambling and diffusion operations based on the initial disturbed image, change the pixel position of the image, and preliminarily change the pixel value of the image to obtain a semi-encrypted image; The bidirectional perturbation index diffusion algorithm is used to perform secondary diffusion on the semi-encrypted image to obtain the encrypted image.

2. According to claim 1, an image encryption method based on a new non-adjacent dynamic coupling mapping grid and cross scrambling is characterized in that: The image is an image with pixels between 0-255.

3. The image encryption method based on a novel non-adjacent dynamic coupling mapping grid and cross scrambling according to claim 1 is characterized in that: The process of processing the image to be processed and obtaining the parameters and initial values ​​required for the encryption process adopts the SHA-512 algorithm.

4. The image encryption method based on a novel non-adjacent dynamic coupling mapping grid and cross scrambling according to claim 1 is characterized in that: The parameters and initial values ​​required for the encryption process are used to generate a chaotic sequence, and the parameters and initial values ​​are used to iterate the sine-exponential non-adjacent dynamic coupling mapping lattice system to obtain a chaotic sequence with a length of M×N, where M and N represent the length and width of the plaintext image respectively; the specific formula of the sine-exponential non-adjacent dynamic coupling mapping lattice system is as follows: Where: e is the coupling coefficient 0≤e≤1, the value range of control parameters μ, e and d is (0,+∞), n (n=1,2,3...) is the time series, i, j and k represent the spatial positions of three non-adjacent grids, p and q are the control parameters of Arnold mapping, and L represents the number of grids.

5. The image encryption method based on a novel non-adjacent dynamic coupling mapping grid and cross scrambling according to claim 1 is characterized in that: The process of using the cross traversal algorithm to select different center points and traversal directions of the image to preliminarily scramble the positions of the image pixels to obtain the initial disturbed image is as follows: S41: intercept some subsequences of the chaotic sequence A1, and sort them respectively to obtain the row index sequence R and column index sequence C of the plaintext image P. The specific formula is as follows: Where: M and N represent the length and width of the plaintext image respectively; S42: Mark the top of the center point as 1, the right as 2, the bottom as 3, and the left as 4 to determine the starting direction S; The specific formula is as follows: S=mod(floor(A1(2L+1:3L)×2 14 ),4)+1 S43: Determine the center points P(R(i), C(i)) at different positions according to the row index R and the column index C, take each center point as the starting point, and traverse all the untraversed pixels in the row and column where the center point is located clockwise according to the corresponding starting direction S, and put them into the one-dimensional sequence P1 in sequence, repeat S41-S43 until all pixels are traversed, and then rearrange the one-dimensional sequence P1 in column priority order to adjust its size to M×N, so as to obtain the initial disturbed image P1.

6. The image encryption method based on a novel non-adjacent dynamic coupling mapping grid and cross scrambling according to claim 1, characterized in that: The random cross transformation algorithm is used to perform scrambling and diffusion operations based on the initial disturbed image, change the pixel position of the image, and preliminarily change the pixel value of the image to obtain a semi-encrypted image. The process is as follows: S51: again intercepting some subsequences of the chaotic sequence A1 and sorting them respectively to obtain different row index sequences AR and column index sequences AC. The specific formula is as follows: S52: According to the following formula, two integer sequences E1 and E2 are obtained for subsequent scrambling operations. At the same time, the chaotic sequences A2 and A3 are processed to obtain two matrices F1 and F2 of size M×N for subsequent diffusion operations. The specific formula is as follows: S53: In each random cross-transformation cycle operation, a row of the image P1 is randomly selected using the row index sequence AR, and two different pixel positions on the row are randomly selected using the integer sequence E1, and then a scrambling operation is performed on the row and column of the selected position, and then a diffusion operation is performed in combination with F1 until the row index sequence AR is completed; similarly, a column of the image P1 is randomly selected using AC, and two different pixel positions on the column are randomly selected using the integer sequence E2, and then a scrambling operation is performed on the row and column of the selected position, and then a diffusion operation is performed in combination with F2 until the column index sequence AC is completed; in addition, a special scrambling process is performed on the outermost rows and columns of the image P1, in which the row is cyclically moved one position to the right and the column is cyclically moved one position downward to obtain a semi-encrypted image P2.

7. The image encryption method based on a novel non-adjacent dynamic coupling mapping grid and cross scrambling according to claim 1 is characterized in that: The process of using the bidirectional perturbation index diffusion algorithm to perform secondary diffusion on the semi-encrypted image to obtain the encrypted image is as follows: S61: First, the chaotic sequence A4 is sorted in ascending order to obtain a global index sequence IA of the image P2. The specific formula is as follows: [~,IA]=sort(A4) S62: Use the chaotic sequence A5 to quickly perturb IA through a quick sorting algorithm to obtain a forward index sequence IB. The forward index sequence IB can be used to generate a backward index sequence IC. The specific formula is as follows: IC=flip(IB) S63: Convert the semi-encrypted image P2 into a one-dimensional sequence p. First, diffuse p using the forward index sequence IB to obtain a one-dimensional sequence c1. Then diffuse c1 using the backward index sequence IC to obtain a one-dimensional sequence c2. The specific formula is as follows: S64: Adjust the one-dimensional sequence c2 to an M×N matrix to obtain the final encrypted image C.

8. An image encryption device based on a new non-adjacent dynamic coupling mapping grid and cross scrambling, characterized in that: include: Acquisition module: used to acquire the image to be processed; Preprocessing module: used to preprocess the image to be processed to obtain the parameters and initial values ​​required for the encryption process; Generation module: used to generate chaotic sequences based on the parameters and initial values ​​required by the encryption process; Initial disturbance module: used to use the cross traversal algorithm to select different center points and traversal directions of the image to perform preliminary scrambling on the positions of the image pixels to obtain the initial disturbed image; Semi-encrypted module: used to perform scrambling and diffusion operations based on the initial disturbed image using a random cross transformation algorithm, change the pixel position of the image, and preliminarily change the pixel value of the image to obtain a semi-encrypted image; Secondary diffusion module: used to perform secondary diffusion on the semi-encrypted image using a bidirectional perturbation index diffusion algorithm to obtain an encrypted image.

9. A computer device comprising: A processor and a memory, wherein the memory stores a program module, wherein the program module runs on the processor to implement the method according to any one of claims 1 to 7.

Images