Image encryption method, system and decryption method based on DNA coding and Arnold transformation

Abstract

The invention belongs to the technical field of image information security, and discloses an image encryption method, system and decryption method based on DNA coding and Arnold transformation. The encryption method comprises the following steps: firstly, segmenting an original image into a plurality of non-overlapping sub-blocks with 2 * 2 pixels, then converting binary pixel values in each sub-block into a DNA base sequence according to a predefined mapping rule, generating a random DNA base sequence through a secret key k1, and carrying out XOR operation to generate modulated encrypted sub-blocks. Then, generating a scrambling sequence through the secret key k2, and carrying out replacement operation on pixel positions in the encrypted sub-blocks; and finally, Arnold transformation is carried out on the scrambled encryption sub-blocks, the global position of pixels is changed, and a final encryption image is generated. The invention further provides a corresponding decryption method and encryption system, through combination of DNA coding and Arnold transformation, multi-level encryption of the image is achieved, the security and practicability of image encryption are improved, and various attack means are effectively resisted.

Description

Technical Field

[0001] The present invention belongs to the technical field of image information security, and particularly relates to an image encryption method, system and decryption method based on DNA coding and Arnold transform. Background Art

[0002] With the wide use of digital images in various applications, the security of image data processing and transmission has increasingly become an urgent problem to be solved. Especially in the cloud storage environment, there is a separation between the image owner and the cloud platform manager, resulting in the vulnerability of image data to unauthorized access and tampering, which affects data privacy and security.

[0003] Currently, the mainstream image encryption methods mainly include encryption technologies based on traditional symmetric encryption algorithms (such as AES, DES, etc.), chaos theory, and DNA coding. Although traditional encryption algorithms are mature and stable in data protection, their computational complexity is relatively high, making it difficult to achieve large-scale real-time image processing. Based on its high sensitivity and randomness, the chaos system provides a new idea for image encryption. However, existing chaos encryption methods still have problems such as insufficient encryption strength and difficult key management. DNA coding technology maps image pixel information to high-entropy DNA base sequences, providing rich coding methods and relatively high security. However, the encryption algorithm using only DNA coding still has deficiencies in anti-attack ability and encryption efficiency.

[0004] In addition, many existing encryption algorithms are not fully implemented in the combination of local pixel confusion and global pixel rearrangement, resulting in their encrypted images being vulnerable to statistical analysis and brute-force attacks. Therefore, there is an urgent need for a new image encryption method that combines multi-level encryption mechanisms, which can not only effectively perturb the local details of the image but also achieve advanced confusion in the overall structure, thereby improving the security and practicality of image encryption. Summary of the Invention

[0005] The purpose of the present invention is to provide an image encryption method, system and decryption method based on DNA coding and Arnold transform, which solve the deficiencies of existing encryption algorithms in computational efficiency, anti-attack ability and applicable scenarios by integrating the bioinformatics characteristics of DNA coding and the chaotic mapping technology of Arnold transform.

[0006] To achieve the above object, according to the design scheme provided by the present invention, on the one hand, an image encryption method based on DNA coding and Arnold transform is provided, including:

[0007] S1. Divide the original image to be encrypted into multiple non-overlapping sub-blocks of 2×2 pixels;

[0008] S2. Convert the binary pixel values in each sub - block into a DNA base sequence according to the predefined mapping rules; generate a random DNA base sequence through the key k1, and perform a bit - by - bit exclusive - OR operation with the DNA base sequence within the sub - block to generate a modulated encrypted sub - block;

[0009] S3. Generate a scrambling sequence through the key k2, and perform a permutation operation on the pixel positions within each modulated encrypted sub - block to generate a scrambled encrypted sub - block;

[0010] S4. Perform an Arnold transform on the scrambled encrypted sub - block, and change the global positions of the pixels through chaotic mapping to generate the final encrypted image;

[0011] As the image encryption method based on DNA coding and Arnold transform of the present invention, further, the mapping rule of the DNA base sequence in step S2 is: binary 00 is mapped to DNA base A, binary 01 is mapped to DNA base T, binary 10 is mapped to DNA base C, and binary 11 is mapped to DNA base G.

[0012] As the image encryption method based on DNA coding and Arnold transform of the present invention, further, both the keys k1 and k2 are generated based on the random number generation method.

[0013] As the image encryption method based on DNA coding and Arnold transform of the present invention, further, the permutation operation in step S3 is: based on the scrambling sequence generated by the key k2, exchange the pixel positions within the sub - block according to the row - first or column - first index order.

[0014] As the image encryption method based on DNA coding and Arnold transform of the present invention, further, the formula for the exclusive - OR operation in step S3 is:

[0015] ;

[0016] where Xi is the pixel value of the original sub - block, Di is the decimal value corresponding to the DNA sequence generated by the key k1, is the pixel value of the modulated encrypted sub - block.

[0017] As the image encryption method based on DNA coding and Arnold transform of the present invention, further, the number of iterations of the Arnold transform in step S4 is 3 to 5 times, and its coordinate transformation formula is:

[0018] ;

[0019] where x and y are the original coordinates of the pixel, x′ and y′ are the transformed coordinates, and M and N are the side lengths of the image.

[0020] On the other hand, the present invention provides an image decryption method based on DNA coding and Arnold transform, which is used to decrypt the encrypted image obtained by the above-mentioned image encryption method based on DNA coding and Arnold transform, and includes the following steps:

[0021] Perform an inverse Arnold transform on the encrypted image to restore the scrambled sub-blocks;

[0022] Use the key k2 to perform an inverse permutation operation on the pixel positions of each sub-block to restore the pixel positions within the sub-block;

[0023] Perform an inverse exclusive OR operation on the DNA sequence through the key k1 to restore the original DNA base sequence;

[0024] Convert the DNA sequence into binary pixel values according to the predefined mapping rules;

[0025] Recombine all sub-blocks into the original image.

[0026] On the other hand, the present invention provides an image encryption system based on DNA coding and Arnold transform, including:

[0027] An image block division module, which is used to divide the input image into multiple non-overlapping 2×2 sub-blocks;

[0028] A DNA coding modulation module, which is used to convert the pixel values of the image sub-blocks into DNA sequences according to the mapping rules and perform exclusive OR modulation using the key k1;

[0029] An in-block scrambling module, which is used to scramble the pixel positions within the sub-blocks based on the scrambling sequence generated by the key k2;

[0030] An Arnold transform module, which is used to perform an Arnold transform on the entire scrambled image to enhance the encryption strength;

[0031] A key management module, including a random number generation sub-module, a key generation sub-module, and a key storage sub-module, which is used to manage the keys k1, k2 and Arnold transform parameters required for encryption and decryption, and realize the secure synchronization and update of the keys.

[0032] The beneficial effects of the present invention are:

[0033] The present invention adopts a block - processing technique, which divides the image into multiple non - overlapping sub - blocks and performs bit - by - bit exclusive - OR operations in combination with dynamically generated DNA sequences. This not only confuses the pixel values but also retains local correlations to avoid the leakage of statistical features. Meanwhile, through the key - driven in - block scrambling operation, the internal structure of the sub - blocks is further destroyed, enhancing the anti - statistical - analysis ability. The introduction of the Arnold transform thoroughly disrupts the global distribution of the image through multiple - iteration global pixel rearrangement, forming a dual - protection mechanism. The pixel - value distribution of the encrypted image is close to a uniform distribution, and the correlation coefficient between adjacent pixels approaches zero, effectively resisting various attack means. In addition, the dual - key mechanism is independently generated, greatly increasing the difficulty of brute - force cracking. The key space is reasonably designed, fully ensuring the security of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic diagram of the encryption process of the image encryption method based on DNA coding and Arnold transform of the present invention;

[0035] Figure 2 is a schematic diagram of the decryption process of the image decryption method based on DNA coding and Arnold transform of the present invention;

[0036] Figure 3 is a schematic diagram of the original image to be encrypted;

[0037] Figure 4 is a schematic diagram of the image encrypted by the image encryption method based on DNA coding and Arnold transform of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] The image encryption method based on DNA coding and Arnold transform proposed by the present invention combines the high - information - entropy characteristics of DNA coding and the chaotic rearrangement technology of Arnold transform, effectively improving the security and anti - attack ability of image encryption. The following details the implementation process and technical details of the present invention in combination with the attached drawings and specific parameters. It should be noted that the following embodiments are explanations and illustrations of the present invention and do not constitute a limitation on the protection scope of the present invention.

[0039] As Figure 1 shown, the present invention proposes an image encryption method based on DNA coding and Arnold transform. This method skillfully combines the bioinformatics characteristics of DNA coding and the chaotic - mapping technology of Arnold transform, aiming to overcome the limitations of existing encryption algorithms in terms of computational efficiency, anti - attack ability, and applicable scenarios.

[0040] The specific implementation process of the encryption method of the present invention includes:

[0041] S1. Divide the original image to be encrypted into non - overlapping sub - blocks with each sub - block size of 2×2 pixels. For an image with size M×N, calculate and divide it into complete sub - blocks. If the image size cannot be evenly divided by 2, use methods such as padding at the image edges, like zero - value padding or mirror extension, to ensure that all divided sub - blocks are complete 2×2 matrices. Each sub - block contains four adjacent pixel units arranged in a row. The image pixel values are stored in binary form and encoded into a continuous binary sequence in row - major order to prepare for subsequent DNA encoding.

[0042] S2. Convert the binary pixel data within each 2×2 sub - block according to a predefined mapping to encode the binary data into a DNA base sequence. Then generate a random DNA base sequence through the key k1 and perform a bit - by - bit exclusive - OR operation with the DNA base sequence within the sub - block to generate a modulated encrypted sub - block.

[0043] Specifically, the mapping rule of the DNA base sequence adopted in the present invention is: binary "00" is mapped to DNA base A, binary "01" is mapped to DNA base T, binary "10" is mapped to DNA base C, and binary "11" is mapped to DNA base G. For example, if a pixel value is the decimal number 65, its corresponding binary number is 01000001. According to the above mapping rule, it can be converted into the DNA sequence "TAGA".

[0044] The key k1 is used to generate a random DNA base sequence with a length corresponding to the number of sub - blocks. By generating the key sequence based on a random number generation algorithm, the randomness and security of encryption are ensured. This random DNA sequence performs a bit - by - bit exclusive - OR operation with the DNA base sequence corresponding to the sub - block to achieve encryption modulation. After calculation using the formula a modulated encrypted image is generated, where is the pixel value of the original sub - block, is the decimal value corresponding to the DNA base sequence generated by the key k1, is the pixel value of the modulated encrypted sub - block. This bit - by - bit exclusive - OR processing realizes the efficient scrambling of pixel values while maintaining a certain local correlation to avoid statistical attacks.

[0045] S3. Use the pseudo-random scrambling sequence generated by the second key k2 based on random number generation technology to perform a permutation operation on the pixel positions within each sub-block. The length of the scrambling sequence is the same as the number of pixels in the sub-block (i.e., length 4), and its generation process also ensures unpredictability based on a random algorithm. According to this scrambling sequence, the pixels are re-ordered within the sub-block in row-major or column-major index order. For example, the sequence [3, 1, 4, 2] means moving the first pixel to the third position, the second pixel to the first position, and so on. This process breaks the natural arrangement relationship of the sub-block pixels and significantly improves the encryption strength.

[0046] S4. Perform an Arnold transform on the scrambled encrypted sub-blocks. As a global pixel space transform based on chaotic mapping, the Arnold transform re-locates the pixel coordinates through multiple iterations, thereby achieving the overall diffusion and confusion of the image pixels. The formula for the Arnold transform is:

[0047] ;

[0048] where, 、 are the original coordinates of the pixel, 、 are the transformed coordinates, 、 are the side lengths of the image. The number of iterations is selected to be 3 to 5 times to balance the encryption strength and computational efficiency. This transform effectively disrupts the global layout of the pixels, making the pixel distribution of the encrypted image tend to be uniform and eliminating obvious statistical structure features.

[0049] As Figure 2 shown, the present invention also provides an image decryption method based on DNA coding and Arnold transform for decrypting the encrypted image obtained by the above encryption method, including the following steps:

[0050] Perform an inverse Arnold transform on the encrypted image to restore the scrambled sub-blocks;

[0051] Use the key k2 to perform an inverse permutation operation on the pixel positions of each sub-block to restore the pixel positions within the sub-block;

[0052] Perform an inverse XOR operation on the DNA sequence through the key k2 to restore the original DNA base sequence;

[0053] Convert the DNA sequence into binary pixel values according to the predefined mapping rules;

[0054] Recombine all sub-blocks into the original image. Re-combine all 2×2 sub-blocks after decryption into a complete image to obtain the original decrypted image.

[0055] Meanwhile, to implement the above encryption method, the present invention also provides an image encryption system based on DNA coding and Arnold transform. The system includes:

[0056] An image block division module, configured to divide an input image into a plurality of non-overlapping 2×2 sub-blocks;

[0057] A DNA coding modulation module, configured to convert the pixel values of the image sub-blocks into DNA sequences according to a mapping rule, and perform exclusive OR modulation using the key k1;

[0058] An in-block scrambling module, configured to scramble the pixel positions within the sub-blocks based on a scrambling sequence generated by the key k2;

[0059] An Arnold transform module, configured to perform Arnold transform processing on the entire scrambled image to enhance the encryption strength;

[0060] A key management module, including a random number generation sub-module, a key generation sub-module, and a key storage sub-module, configured to manage the keys k1, k2, and Arnold transform parameters required for encryption and decryption, and implement secure synchronization and update of the keys.

Claims

1. An image encryption method based on DNA encoding and Arnold transform, characterized in that Including: S1. Divide the original image to be encrypted into multiple non - overlapping 2×2 pixel sub - blocks; S2. Convert the binary pixel values in each sub - block into a DNA base sequence according to a predefined mapping rule; generate a random DNA base sequence through the key k1, and perform a bit - by - bit exclusive - OR operation with the DNA base sequence within the sub - block to generate a modulated encrypted sub - block; S3. Generate a scrambling sequence through the key k2, and perform a permutation operation on the pixel positions within each modulated encrypted sub - block to generate a scrambled encrypted sub - block; S4. Perform an Arnold transform on the scrambled encrypted sub - blocks, and change the global positions of the pixels through chaotic mapping to generate the final encrypted image.

2. The image encryption method according to claim 1, wherein The mapping rule of the DNA base sequence described in step S2 is: binary 00 is mapped to DNA base A, binary 01 is mapped to DNA base T, binary 10 is mapped to DNA base C, and binary 11 is mapped to DNA base G.

3. The image encryption method according to claim 1, wherein The keys k1 and k2 are both generated based on a random number generation method.

4. The image encryption method according to claim 1, characterized in that The permutation operation described in step S3 is: based on the scrambling sequence generated by the key k2, exchange the pixel positions within the sub - block according to the row - first or column - first index order.

5. The image encryption method according to claim 1, characterized in that The formula for the exclusive - OR operation described in step S3 is: ； Among them, Xi is the pixel value of the original sub-block, and Di is the decimal value corresponding to the DNA sequence generated by the key k1, which is the pixel value of the encrypted sub-block after modulation.

6. The image encryption method according to claim 1, wherein The number of iterations of the Arnold transform described in step S4 is 3 to 5 times, and its coordinate transformation formula is: ； Where x, y are the original coordinates of the pixel, and x′, y′ are the transformed coordinates, and M, N are the side lengths of the image.

7. An image decryption method based on DNA encoding and Arnold transform, characterized in that, Decrypting the encrypted image obtained by the image encryption method based on DNA coding and Arnold transform according to any one of claims 1 - 6 includes the following steps: Perform an inverse Arnold transform on the encrypted image to restore the scrambled sub - blocks; Use the key k2 to perform an inverse permutation operation on the pixel positions of each sub - block to restore the pixel positions within the sub - block; Perform an inverse exclusive - OR operation on the DNA sequence through the key k1 to restore the original DNA base sequence; Convert the DNA sequence into binary pixel values according to the predefined mapping rule; Recombine all sub - blocks into the original image.

8. An image encryption system based on DNA coding and Arnold transform, characterized in that, To implement the method described in any one of claims 1 - 6, it includes: An image segmentation module for dividing the input image into multiple non - overlapping 2×2 sub - blocks; A DNA coding modulation module for converting the pixel values of the image sub - blocks into DNA sequences according to the mapping rule and performing exclusive - OR modulation using the key k1; An in - block scrambling module for scrambling the pixel positions within the sub - block based on the scrambling sequence generated by the key k2; An Arnold transform module for performing an Arnold transform on the entire scrambled image to enhance the encryption intensity; A key management module, including a random number generation sub - module, a key generation sub - module, and a key storage sub - module, for managing the keys k1, k2 and Arnold transform parameters required for encryption and decryption, and realizing the secure synchronization and update of the keys.

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