CN115103080B - Image encryption method and system based on DNA triploid variation - Google Patents

Abstract

The invention relates to the technical field of data security, in particular to an image encryption method and system based on DNA triploid variation. The method comprises the following steps: obtaining an image to be encrypted to generate a plaintext associated random key, generating an integer random sequence based on a double-chaotic system, performing DNA encoding on the plaintext image to be encrypted, performing DNA triploid variant encryption on the image encoding matrix, performing DNA decryption on the encoding matrix after variant encryption, and performing secondary encryption on the decoded image by using diffusion operation. According to the scheme, the security protection of the privacy information of the image is realized by carrying out DNA triploid encryption on the image, the security of the encryption method is improved, the risk of image data leakage is effectively reduced, and the encryption method can effectively resist plaintext attack.

Description

Image encryption method and system based on DNA triple mutation

Technical Field

The present invention relates to the technical field of data security, and in particular to an image encryption method and system based on DNA triple mutation.

Background Art

In recent years, with the continuous deepening of multimedia technology applications, the privacy protection issue in image data has attracted more and more attention. The widespread application of multimedia data has greatly facilitated people's daily lives. However, the widespread use of audio, image and video data on the Internet has brought potential risks of information leakage.

In special fields such as government, military and medical, the privacy protection of image information is particularly important. In order to prevent illegal third parties from obtaining and accessing confidential information in images, the research on image encryption algorithms has become imperative. However, traditional methods for text encryption such as DES and AES are not suitable for image data with high redundancy and large capacity.

In recent years, DNA coding-based image encryption technology has attracted increasing attention due to its high parallelism and large storage characteristics. DNA coding-based image encryption technology can effectively protect the information in the image. However, there are three major defects in the existing DNA encryption methods, which pose potential security threats: (1) The security of DNA encryption algorithms using low-dimensional chaotic systems is insufficient. The key space of these encryption algorithms is very small and cannot resist brute force attacks; (2) There are only a few simple types of operations in existing DNA sequence operations. The DNA operations used in most current DNA encryption schemes are only DNA addition, DNA subtraction, DNA XOR, DNA complementation, and DNA circular shift. The application of limited types of DNA sequence operations makes the encryption algorithm predictable and easy to crack; (3) The resistance to chosen plaintext attacks is relatively poor. The design of the encryption algorithm is independent of the input image, and the key stream used when encrypting different images is fixed. This makes the encryption algorithm vulnerable to chosen plaintext attacks and the security of the encryption system is weak.

Summary of the invention

In order to solve the technical problems existing in the prior art, the present invention provides an image encryption method and system based on DNA triple mutation. The present invention introduces DNA triple mutation encryption by combining the SHA-256 hash algorithm and the image encryption algorithm based on DNA coding. By combining the dual chaotic system, the operation types of the DNA encryption algorithm are enriched, the security of the encryption algorithm is improved, the risk of image data leakage is effectively reduced, and the encryption algorithm can effectively resist plaintext attacks.

The first object of the present invention is to provide an image encryption method based on DNA triple mutation.

The second object of the present invention is to provide an image encryption system based on DNA triple mutation.

The first object of the present invention can be achieved by adopting the following technical solutions:

An image encryption method based on DNA triple mutation, the method comprising:

S1. Combine the plaintext image to be encrypted with the SHA-256 hash algorithm, and generate a 256-bit hash value through the SHA-256 hash algorithm; set the initial key of the chaotic system, decompose the hash value into several bit blocks, and obtain the initial value of the chaotic system associated with the plaintext through the operation of several bit blocks and the initial key;

S2, substituting the initial value of the chaotic system into the two-dimensional Logistic adjusted sine map and the four-dimensional quadratic autonomous hyperchaotic system, generating two groups of chaotic sequences, discarding a predetermined number of random numbers in the first half of the chaotic sequence, preprocessing the two groups of chaotic sequences, and obtaining multiple integer random sequences;

S3, decomposing the plaintext image to be encrypted into three channel planes of RGB, and dynamically encoding each pixel of the three channel planes using an integer random sequence to obtain three DNA coding matrices;

S4, dynamically selecting a DNA triple mutation rule according to an integer random sequence, performing triple mutation conversion on each DNA base in the three DNA encoding matrices, and obtaining three encrypted DNA encoding matrices;

S5, using an integer random sequence to decode the three encrypted DNA matrices, converting the DNA base matrices into decimal pixels between 0 and 255, and obtaining three decoded images;

S6. Use an integer random sequence to perform secondary diffusion encryption on the decoded image and fuse the three channel planes to obtain a color ciphertext image.

The second object of the present invention can be achieved by adopting the following technical solutions:

An image encryption system based on DNA triple mutation, comprising:

The operation module is used to combine the plaintext image to be encrypted with the SHA-256 hash algorithm to generate a 256-bit hash value through the SHA-256 hash algorithm; set the initial key of the chaotic system, decompose the hash value into a number of bit blocks, and obtain the initial value of the chaotic system associated with the plaintext through the operation of the several bit blocks and the initial key;

A generation module is used to substitute the initial value of the chaotic system into the two-dimensional Logistic adjusted sine map and the four-dimensional quadratic autonomous hyperchaotic system to generate two groups of chaotic sequences, discard a predetermined number of random numbers in the first half of the chaotic sequence, pre-process the two groups of chaotic sequences, and obtain multiple integer random sequences;

The encoding module is used to decompose the plaintext image to be encrypted into three channel planes of RGB, and dynamically encode each pixel of the three channel planes using an integer random sequence to obtain three DNA encoding matrices;

An encryption module is used to dynamically select a DNA triple mutation rule according to an integer random sequence, perform triple mutation conversion on each DNA base in three DNA encoding matrices, and obtain three encrypted DNA encoding matrices;

A decoding module, used to decode the three encrypted DNA matrices using an integer random sequence, convert the DNA base matrices into decimal pixels between 0 and 255, and obtain three decoded images;

The secondary diffusion encryption module is used to perform secondary diffusion encryption on the decoded image using an integer random sequence and fuse the three channel planes to obtain a color ciphertext image.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The present invention combines the SHA-256 hash algorithm, and the key stream generated by the encryption algorithm is associated with the plaintext image. When the plaintext image changes, the key stream will change greatly, so that the encryption algorithm can effectively resist plaintext attacks;

2. The present invention introduces DNA triple mutation encryption through an image encryption algorithm based on DNA coding, enriches the operation types of the DNA encryption algorithm, improves the security of the encryption algorithm, and effectively reduces the risk of image data leakage;

3. The present invention increases the key space of the encryption algorithm by combining a dual chaotic system. Under the computing power of existing computers, brute force attacks cannot traverse all possible keys to crack the encryption algorithm.

BRIEF DESCRIPTION OF THE DRAWINGS

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 only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

FIG1 is a basic flow chart of an image encryption method according to an embodiment of the present invention;

FIG2 is an overall architecture diagram of an image encryption method according to an embodiment of the present invention;

FIG3 is a schematic diagram of a DNA triploid variation in one embodiment of the present invention;

FIG4 is a schematic diagram of the superposition of DNA coding chains of a DNA triple mutation in one embodiment of the present invention;

FIG5 is a diagram showing the encryption and decryption effects in one embodiment of the present invention;

FIG6 is a schematic diagram showing a comparison of histograms of images before and after encryption and decryption in one embodiment of the present invention.

DETAILED DESCRIPTION

The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is obvious that the described embodiments are part of the embodiments of the present invention, not all of the embodiments, and the implementation of the present invention is not limited to this. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Example 1

As shown in FIG1 , the image encryption method based on DNA triple mutation of the present invention comprises the following steps:

S1: Set the initial key and apply the SHA-256 hash algorithm to generate the initial value of the chaotic system associated with the plaintext. Combine the plaintext image to be encrypted with the SHA-256 algorithm, generate a 256-bit hash value through the hash algorithm, set the initial key of the chaotic system, decompose the hash value into several bit blocks, and obtain the initial value of the chaotic system associated with the plaintext through several bit blocks and the initial key operation.

Preferably, the plaintext image is used as input to the SHA-256 hash algorithm to generate a 256-bit hash value K, and the 256-bit hash value K is decomposed into 32-bit blocks:

K＝K ₁ ,K ₂ ,K ₃ ,…,K _32;

After the initial key of the chaotic system is set, the hash value is decomposed into a number of bit blocks, and the initial value of the chaotic system associated with the plain text is obtained by operating the number of bit blocks with the initial key.

Each bit block K _i (i=1, 2, ..., 32) consists of 8 bits and corresponds to a decimal number between 0 and 255. Multiple intermediate variables are generated through the bit blocks. In this embodiment, these bit blocks are used to generate the following 6 intermediate variables related to the plaintext:

表示逐位异或运算，中间变量ε_i∈[0,1](i＝1,2,…,6)。in

Represents a bitwise XOR operation, with the intermediate variable ε _i ∈[0,1](i＝1,2,…,6).

Preferably, the intermediate variable generated by the above bit block is used to update the key and obtain the initial value of the chaotic system associated with the plaintext, ensuring that the initial value of the chaotic system is completely different each time the plaintext image to be encrypted changes.

The initial key is set to u ₀ , t ₀ , x ₀ , y ₀ , z ₀ , w ₀ , and the key is updated by combining the initial key with _Ki (i=1, 2, ..., 32) to obtain the initial value of the chaotic system associated with the plaintext.

Among them, the initial value of the two-dimensional Logistic adjusted sine map is updated as:

The initial value of the four-dimensional quadratic autonomous hyperchaotic system is updated as:

S2: Iterate the two-dimensional Logistic adjusted sine map and the four-dimensional quadratic autonomous hyperchaotic system to generate multiple integer random sequences associated with plaintext. Substitute the initial value of the chaotic system into the two-dimensional Logistic adjusted sine map and the four-dimensional quadratic autonomous hyperchaotic system to generate two sets of chaotic sequences, discard a certain number of random numbers in the first half of the chaotic sequence to reduce the problem of uneven random number distribution caused by the transient effect of the chaotic system; preprocess the two sets of chaotic sequences and convert them into integer random sequences for encoding, decoding and encryption.

Specifically, the generation of chaotic sequences is divided into two parts, including the generation of chaotic sequences by two-dimensional Logistic-adjusted sine mapping and the generation of chaotic sequences by four-dimensional quadratic autonomous hyperchaotic system. In the two-dimensional Logistic-adjusted sine mapping, the output of the Logistic mapping is used as an additional item to the input of the sine mapping; the modulation of the two mappings derives a more complex motion trajectory of the chaotic system and increases the complexity of the chaotic behavior. The two-dimensional Logistic-adjusted sine mapping is:

Among them, u and t are the state variables that generate chaotic sequences, and u, t∈[0,1]; i＝0,1,2,3...; μ is the parameter of the system, and μ∈[0.44,0.93].

The iterative equation of the four-dimensional quadratic autonomous hyperchaotic system is:

Among them, x, y, z, w are state variables that generate chaotic sequences; i = 0, 1, 2, 3...; a, b, c, d, e are constant parameters, and a = 10, b = 28, c = 8/3, d = 1, e = 16.

Preferably, the initial value of the chaotic system associated with the plain text obtained in step 1 is used as the initial value of the two-dimensional Logistic adjusted sine map and the four-dimensional quadratic autonomous hyperchaotic system, and the two chaotic systems are iterated respectively to generate 6 chaotic sequences of a certain length.

In this embodiment, firstly, u′ ₀ and t ₀ ′ generated in step 1 are used as the initial values of the two-dimensional Logistic adjusted sine mapping, and x′ ₀ , y′ ₀ , z′ ₀ , w′ ₀ are used as the initial values of the four-dimensional quadratic autonomous hyperchaotic system, and the chaotic system is iterated. Assuming that the size of the plaintext image is M×N×3, the number of iterations of the two-dimensional Logistic adjusted sine mapping is M×N+1000, and the number of iterations of the four-dimensional quadratic autonomous hyperchaotic system is M×4N+1000, generating 6 random sequences U, T, X, Y, Z and W.

Secondly, preferably, the first 1000 random numbers of the chaotic sequence are discarded, and the random numbers starting from the 1001th position are taken as the chaotic sequence used subsequently to avoid the problem of uneven random number distribution caused by the transient effect of the chaotic system; the first M×N elements are intercepted from U, T, X, Z, and W, and the first M×4N elements are intercepted from Y to obtain the following 6 chaotic sequences of specific lengths:

Finally, the two groups of chaotic sequences are preprocessed and converted into integer random sequences X, Y, Z, W, U and T:

Among them, x(i), y(i), z(i), w(i), u(i), t(i) are the i-th elements of the integer random sequences X, Y, Z, W, U and T; round(a) means obtaining the integer closest to a through the rounding rule; mod(a, b) means the modulus operation of a on b.

S3: Decompose the plaintext image to be encrypted into three channel planes of RGB, and use integer random sequences to dynamically encode each pixel of the three channel planes to obtain three DNA coding matrices. Each pixel is decomposed into 8 bits, and every two bits are encoded into one of the four forms of DNA bases A, T, C, and G according to the DNA coding rules. The DNA coding rules are randomly determined by the elements in the integer random sequence.

As shown in Figure 2, assuming that the size of each channel plane is M×N, all elements of the RGB channel planes are DNA encoded respectively, each pixel is decomposed into 8 bit planes, and every two bits are encoded into DNA bases according to the DNA encoding rules, which are encoded into 4 DNA bases, namely A base (adenine), C base (cytosine), G base (guanine) and T base (thymine). Each base is represented by a 2-bit binary number 00, 01, 10 or 11.

The DNA encoding rules are dynamically selected from the integer random sequence X, and three DNA encoding matrices R _b , G _b , and B _b are obtained:

Where i = 1, 2, ..., M; j = 1, 2, ..., N; DNA _b (a, b) represents the mapping of converting an 8-bit decimal pixel a into four DNA bases using encoding rule b.

In Figure 2, the plaintext image to be encrypted is subjected to the SHA-256 hash algorithm to obtain a 256-bit hash value, which is used to update the initial key and generate the initial value of the chaotic system associated with the plaintext. The two-dimensional Logistic adjusted sine map and the four-dimensional quadratic autonomous hyperchaotic system iteratively generate chaotic random sequences X, Y, Z, W, U and T, which are used in various steps of image encryption. The image encryption process is specifically to first decompose the plaintext into RGB components, and then perform DNA dynamic encoding on the RGB components to obtain the DNA matrix. The rules of DNA triple mutation and DNA dynamic decoding are determined by the random sequence, and the image is preliminarily encrypted to obtain an intermediate encrypted image. Then, the image is subjected to cross-row and column scrambling and pixel scrambling, and finally the RGB components are combined to obtain the final ciphertext image.

Specifically, according to the Watson-Crick base complementary pairing principle, the DNA coding rules include 8 DNA coding rules, as shown in Table 1:

Table 1

Preferably, for each pixel in the R, G, and B channel planes of the image, an integer random sequence is used to randomly select one of eight rules for encoding, and a single pixel is converted into four DNA bases in the form of A, T, C, and G, thereby obtaining a DNA encoding matrix.

The DNA encoding rules are dynamically selected from the integer random sequence X, and three DNA encoding matrices R _b , G _b , and B _b are obtained:

Where i = 1, 2, ..., M; j = 1, 2, ..., N; DNA _b (a, b) represents the mapping of converting an 8-bit decimal pixel a into four DNA bases using encoding rule b.

S4: Dynamically select DNA triple mutation rules according to the integer random sequence, perform triple mutation conversion on each DNA base in the three DNA encoding matrices, and obtain three encrypted DNA encoding matrices. Dynamically select DNA triple mutation rules according to the integer random sequence, randomly convert DNA bases in the form of A, T, C, and G into one of the four bases according to the mutation rules, and realize triple mutation encryption of DNA coding.

Preferably, for each pixel in the R, G, and B channels of the image, a chaotic sequence is used to randomly select one of eight rules for encoding, and a single pixel is converted into four DNA bases in the form of A, T, C, and G, thereby obtaining a DNA encoding matrix.

In step 4, the DNA triploid mutation copies each base into three completely identical bases, which are then superimposed on each other to generate new bases.

Specifically, corresponding to the 8 DNA encoding rules, there are 8 DNA triplet mutation rules (mutation methods). The complete DNA triplet mutation rules are shown in Table 2:

Table 2

Preferably, for each base in the DNA coding matrix, an integer random sequence is used to randomly select one of 8 rules for triploid variation conversion, and the single base is converted into any one of A, T, C, and G to obtain an encrypted DNA coding matrix.

Preferably, for each base in the DNA coding matrix, a chaotic sequence is used to randomly select one of eight rules for triploid variation conversion, and a single base is converted into any one of A, T, C, and G to obtain an encrypted DNA coding matrix.

The sizes of DNA encoding matrices R _b , G _b , B _b and integer sequence Y are all M×4N. For each nucleotide base in R _b , G _b and B _b , encryption operation is performed by randomly selecting DNA triple mutation rules from Table 2 using Y. DNA bases in the form of A, T, C, and G are randomly converted into one of the four bases according to the mutation rules, and three DNA triple encryption matrices R _s , G _s and B _s with sizes of M×4N are obtained.

Where i = 1, 2, ..., M; j = 1, 2, ..., 4N; DNA _s (a, b) means performing a DNA triple mutation operation on a using rule b.

As shown in Figure 3, it is a schematic diagram of DNA triploid mutation. After encoding the image into a DNA coding chain, it is copied into three copies and superimposed to generate an encrypted DNA coding chain. As shown in Figure 4, it is a schematic diagram of the superposition of DNA coding chains. First, the DNA bases are converted into binary form according to the DNA coding rules, and the three binary codes are summed to obtain a new code, which is then converted into an encrypted DNA base.

S5: Decode the three encrypted DNA matrices using an integer random sequence, thereby converting the DNA base matrices in the form of A, T, C, and G into decimal pixels between 0 and 255, and obtaining three decoded images. Every four bases are decoded into one decimal pixel, and the decoding rule is dynamically selected by an integer random sequence that is different from that in step three.

The decoding method of the DNA matrix corresponds to the DNA encoding method in Table 1, and there are 8 decoding rules in total.

Preferably, for each encrypted base, a rule is dynamically selected from eight rules using an integer random sequence for decoding, four adjacent bases are sequentially decoded into an 8-bit binary number, and converted into a decimal number between 0 and 255 to obtain a decoded image.

Use the elements in the integer random sequence Z to dynamically select one of the eight rules in Table 1 to decode _Rs , _Gs and _Bs. Every four adjacent bases are decoded into a decimal pixel, and the decoded images _Rj , _Gj and _Bj of three channels with a size of M×N are obtained:

Where i = 1, 2, ..., M; j = 1, 2, ..., N; DNA _j (a, b) is the decoding map.

S6: Use an integer random sequence to perform secondary diffusion encryption on the decoded image and fuse the three channel planes to obtain the final color ciphertext image.

Preferably, the decoded image is first converted into a one-dimensional vector, and then the elements in the one-dimensional vector are XORed with an integer random sequence in order, and XOR-diffused with the encrypted pixel at the previous position; after the diffusion operation is completed, the secondary encrypted vector is converted into a two-dimensional image matrix to obtain a color ciphertext image.

In this embodiment, the three decoded images are first converted into three one-dimensional vectors R ₁ , G ₁ and B ₁ , and three different integer random sequences U, T and W are used to perform different diffusion operations on the three one-dimensional vectors from left to right; for each element, an XOR operation is first performed with a chaotic random number, and then the result is diffused with the previous encrypted element to obtain encrypted vectors R _c1 , G _c1 and B _c1 :

Where i = 2, 3, ..., M. Then the three vectors R _c1 , G _c1 and B _c1 are reshaped into M×N two-dimensional image matrices R _c , G _c and B _c . After the diffusion operation is completed, the three channel planes are fused to obtain a color ciphertext image of size M×N×3.

As shown in FIG5 , it is an encryption and decryption effect diagram in this embodiment, which shows a plaintext image to be encrypted, a ciphertext image, and a decrypted image.

As shown in FIG6 , it is a schematic diagram of the histogram comparison of the image before and after encryption and decryption in this embodiment, wherein FIG6 (a), (b), and (c) are the histograms of the R, G, and B channel planes of the plaintext image, respectively, and FIG6 (d), (e), and (f) are the histograms of the R, G, and B channel planes of the ciphertext image, respectively.

Embodiment 2:

An image encryption system based on DNA triple mutation, the system includes a calculation module, a generation module, a coding module, an encryption module, a decoding module and a secondary diffusion encryption module, the specific functions of each module are as follows:

The operation module is used to combine the plaintext image to be encrypted with the SHA-256 hash algorithm to generate a 256-bit hash value through the SHA-256 hash algorithm; set the initial key of the chaotic system, decompose the hash value into a number of bit blocks, and obtain the initial value of the chaotic system associated with the plaintext through the operation of the several bit blocks and the initial key;

A generation module is used to substitute the initial value of the chaotic system into the two-dimensional Logistic adjusted sine map and the four-dimensional quadratic autonomous hyperchaotic system to generate two groups of chaotic sequences, discard a predetermined number of random numbers in the first half of the chaotic sequence, pre-process the two groups of chaotic sequences, and obtain multiple integer random sequences;

The encoding module is used to decompose the plaintext image to be encrypted into three channel planes of RGB, and dynamically encode each pixel of the three channel planes using an integer random sequence to obtain three DNA encoding matrices;

An encryption module is used to dynamically select a DNA triple mutation rule according to an integer random sequence, perform triple mutation conversion on each DNA base in three DNA encoding matrices, and obtain three encrypted DNA encoding matrices;

A decoding module, used to decode the three encrypted DNA matrices using an integer random sequence, convert the DNA base matrices into decimal pixels between 0 and 255, and obtain three decoded images;

The secondary diffusion encryption module is used to perform secondary diffusion encryption on the decoded image using an integer random sequence and fuse the three channel planes to obtain a color ciphertext image.

The step of combining the plaintext image to be encrypted with the SHA-256 hash algorithm and generating a 256-bit hash value through the SHA-256 hash algorithm comprises: using the plaintext image to be encrypted as input data of the SHA-256 hash algorithm and generating a 256-bit hash value K through the SHA-256 hash algorithm;

The method of setting the initial key of the chaotic system, decomposing the hash value into a plurality of bit blocks, and obtaining the initial value of the chaotic system associated with the plain text by calculating the plurality of bit blocks and the initial key comprises: setting the initial key of the chaotic system, decomposing the hash value into 32 bit blocks, each bit block consisting of 8 bits, generating 6 intermediate variables through the bit blocks, and the intermediate variables are used to update and obtain the initial value of the chaotic system associated with the plain text;

The method of dynamically encoding each pixel of the three channel planes using an integer random sequence includes: decomposing each pixel into 8 bits, and encoding every two bits into a DNA base using a DNA coding rule;

The DNA bases include four forms, which are A base, T base, C base and G base, and each DNA base is represented by a 2-bit binary number.

The DNA encoding rules include 8 DNA encoding rules. For each pixel in the R, G, and B channel planes of the plaintext image to be encrypted, an integer random sequence is used to randomly select one from the 8 DNA encoding rules to encode the pixel, and a single pixel is converted into 4 DNA bases in the form of A, T, C, and G to obtain a DNA encoding matrix.

The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims (9)

1. An image encryption method based on DNA triploid variation is characterized by comprising the following steps:

s1, combining a plaintext image to be encrypted with an SHA-256 hash algorithm, and generating a 256-bit hash value through the SHA-256 hash algorithm; setting an initial key of the chaotic system, decomposing the hash value into a plurality of bit blocks, and calculating the initial key through the bit blocks and the initial key to obtain an initial value of the chaotic system associated with a plaintext;

s2, substituting an initial value of the chaotic system into a two-dimensional Logistic adjustment sinusoidal mapping and four-dimensional secondary autonomous hyper-chaotic system to generate two groups of chaotic sequences, discarding a random number of a preset number in the first half part of the chaotic sequences, and preprocessing the two groups of chaotic sequences to obtain a plurality of integer random sequences;

s3, decomposing a plaintext image to be encrypted into three RGB channel planes, and dynamically encoding each pixel of the three channel planes by using an integer random sequence to obtain three DNA encoding matrixes;

s4, dynamically selecting a DNA triploid variation rule according to the integer random sequence, and performing triploid variation conversion on each DNA base in the three DNA coding matrixes to obtain three encrypted DNA coding matrixes;

s5, decoding the three encrypted DNA matrixes by using an integer random sequence, and converting the DNA base matrixes into decimal pixels between 0 and 255 to obtain three decoded images;

s6, performing secondary diffusion encryption on the decoded image by using an integer random sequence, and fusing three channel planes to obtain a color ciphertext image;

the DNA triploid mutation rule corresponds to a DNA coding rule, the DNA triploid mutation rule comprises 8 DNA triploid mutation rules, for each DNA base in the DNA coding matrix, one DNA base is randomly selected from the 8 DNA triploid mutation rules by using an integer random sequence to perform triploid mutation conversion, and a single DNA base is converted into any one of an A base, a T base, a C base and a G base to obtain an encrypted DNA coding matrix;

the performing triploid variant switching on each DNA base in the three DNA coding matrices comprises: each DNA base is replicated to three identical DNA bases, and the three identical DNA bases are superimposed on each other to create a new base.

2. The method for encrypting an image based on DNA triploid variation according to claim 1, wherein: the step S1 includes: taking a plaintext image to be encrypted as input data of an SHA-256 hash algorithm, and generating a 256-bit hash value K through the SHA-256 hash algorithm; an initial key of the chaotic system is set, the hash value is decomposed into 32 bit blocks, each bit block consists of 8 bits, 6 intermediate variables are generated through the bit blocks, and the intermediate variables are used for updating and acquiring initial values of the chaotic system associated with plaintext.

3. The method for encrypting an image based on DNA triploid variation according to claim 1, wherein: the two-dimensional Logistic-adjusted sinusoidal mapping is described as:

wherein u and t are state variables that produce a chaotic sequence, and u, t e [0,1]; i=0, 1,2, 3; mu is a parameter of the system and mu epsilon [0.44,0.93];

the iterative equation of the four-dimensional quadratic autonomous hyper-chaotic system is described as:

x, y, z, w is a state variable that produces a chaotic sequence; i=0, 1,2, 3; a. b, c, d, e is a constant parameter and a=10, b=28, c=8/3, d=1, e=16.

4. A method of encrypting an image based on DNA triploid variation as claimed in claim 3, wherein: the random numbers of the preset number of the first half part of the discarded chaotic sequence are specifically the first 1000 values of the discarded chaotic sequence, and the random numbers from the 1001 st bit are taken as the subsequently used chaotic sequence;

the chaotic sequence is preprocessed to obtain six integer random sequences, namely an integer random sequence X, Y, Z, W, U and T:

wherein x (i), y (i), z (i), w (i), u (i), T (i) are the i-th elements of the integer random sequences X, Y, Z, W, U and T, respectively; round (a) represents an integer nearest to a by a rounding rule; mod (a, b) represents a modulo operation of a on b.

5. The method for encrypting an image based on DNA triploid variation according to claim 1, wherein: the dynamically encoding each pixel of the three channel planes using an integer random sequence includes: decomposing each pixel into 8 bits, wherein each two bits are encoded into a DNA base by a DNA encoding rule;

the DNA base comprises 4 forms, wherein the 4 forms of the DNA base are respectively an A base, a T base, a C base and a G base, and each DNA base is represented by a 2-bit binary number;

the DNA coding rules comprise 8 DNA coding rules, and for each pixel in a R, G, B channel plane of a plaintext image to be encrypted, an integer random sequence is used for randomly selecting one from the 8 DNA coding rules to code the pixel, and a single pixel is converted into 4 DNA bases to obtain a DNA coding matrix.

6. The method for encrypting an image based on DNA triploid variation according to claim 5, wherein: the step S5 includes: and dynamically selecting a decoding rule corresponding to the rule of DNA coding by using an integer random sequence for decoding each encrypted DNA base, sequentially decoding four adjacent DNA bases into an 8-bit binary number, and converting the 8-bit binary number into decimal number pixels between 0 and 255 to obtain a decoded image.

7. The method for encrypting an image based on DNA triploid variation according to claim 1, wherein: the step S6 includes: converting the decoded image into a one-dimensional vector, performing exclusive-or operation on elements in the one-dimensional vector and the integer random sequence in sequence, and performing exclusive-or diffusion on the elements and the encrypted pixels in the previous position; after the diffusion operation is completed, the secondary encryption vector is converted into a two-dimensional image matrix, and three channel planes are combined to obtain a color ciphertext image.

8. An image encryption system based on DNA triploid variation, the system comprising:

the operation module is used for combining the plaintext image to be encrypted with the SHA-256 hash algorithm and generating a 256-bit hash value through the SHA-256 hash algorithm; setting an initial key of the chaotic system, decomposing the hash value into a plurality of bit blocks, and calculating the initial key through the bit blocks and the initial key to obtain an initial value of the chaotic system associated with a plaintext;

the generation module is used for substituting the initial value of the chaotic system into the two-dimensional Logistic adjustment sinusoidal mapping and the four-dimensional secondary autonomous hyper-chaotic system to generate two groups of chaotic sequences, discarding the random numbers of the preset number of the first half part of the chaotic sequences, and preprocessing the two groups of chaotic sequences to obtain a plurality of integer random sequences;

the coding module is used for decomposing a plaintext image to be encrypted into three RGB channel planes, and dynamically coding each pixel of the three channel planes by using an integer random sequence to obtain three DNA coding matrixes;

the encryption module is used for dynamically selecting a DNA triploid variation rule according to the integer random sequence, executing triploid variation conversion on each DNA base in the three DNA coding matrixes and obtaining three encrypted DNA coding matrixes;

the decoding module is used for decoding the three encrypted DNA matrixes by using the integer random sequence, converting the DNA base matrixes into decimal pixels between 0 and 255, and obtaining three decoded images;

the secondary diffusion encryption module is used for carrying out secondary diffusion encryption on the decoded image by using an integer random sequence and fusing three channel planes to obtain a color ciphertext image;

the DNA triploid mutation rule corresponds to a DNA coding rule, the DNA triploid mutation rule comprises 8 DNA triploid mutation rules, for each DNA base in the DNA coding matrix, one DNA base is randomly selected from the 8 DNA triploid mutation rules by using an integer random sequence to perform triploid mutation conversion, and a single DNA base is converted into any one of an A base, a T base, a C base and a G base to obtain an encrypted DNA coding matrix;

the performing triploid variant switching on each DNA base in the three DNA coding matrices comprises: each DNA base is replicated to three identical DNA bases, and the three identical DNA bases are superimposed on each other to create a new base.

9. An image encryption system based on DNA triploid variation as set forth in claim 8, wherein,

combining the plaintext image to be encrypted with a SHA-256 hash algorithm, generating a 256-bit hash value through the SHA-256 hash algorithm, and comprising: taking a plaintext image to be encrypted as input data of an SHA-256 hash algorithm, and generating a 256-bit hash value K through the SHA-256 hash algorithm;

the method for setting the initial key of the chaotic system, decomposing the hash value into a plurality of bit blocks, and obtaining the initial value of the chaotic system associated with the plaintext through the operation of the bit blocks and the initial key comprises the following steps: setting an initial key of the chaotic system, decomposing a hash value into 32 bit blocks, wherein each bit block consists of 8 bits, and generating 6 intermediate variables through the bit blocks, wherein the intermediate variables are used for updating and acquiring initial values of the chaotic system associated with a plaintext;

the dynamically encoding each pixel of the three channel planes using an integer random sequence includes: decomposing each pixel into 8 bits, wherein each two bits are encoded into a DNA base by a DNA encoding rule;

the DNA base comprises 4 forms, wherein the 4 forms of the DNA base are respectively an A base, a T base, a C base and a G base, and each DNA base is represented by a 2-bit binary number;

the DNA coding rules comprise 8 DNA coding rules, and for each pixel in a R, G, B channel plane of a plaintext image to be encrypted, an integer random sequence is used for randomly selecting one from the 8 DNA coding rules to code the pixel, and a single pixel is converted into 4 DNA bases to obtain a DNA coding matrix.

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