A color image encryption and decryption method based on Logistic double-pixel rectangle mapping

Abstract

The present invention relates to the technical field of information security and image processing, and proposes a color image encryption and decryption method. The method can quickly complete the encryption and decryption of various color images, and the encrypted ciphertext image destroys the structure of the plaintext image, and can effectively resist the image pixel frequency statistical attack. The color image encryption method first constructs a color key image to control the encryption algorithm and the decryption algorithm; secondly, the plaintext color image is preprocessed by using a Logistic chaotic system, and then in each channel of the plaintext image, double pixels are used as groups to search for ciphertext pixels in the rectangle formed by the key image, and finally the ciphertext color image is output. The method has high encryption efficiency and strong practicality, can effectively resist frequency statistical attacks and selected plaintext attacks, and has a good encryption effect. The present invention can be applied to the generation, storage, transmission and other scenes of color images to effectively protect their confidentiality.

Description

Technical Field

[0001] The invention relates to the field of information security, and more specifically, to a color image encryption and decryption method based on Logistic double-pixel rectangle mapping. Background Art

[0002] At present, computer networks and multimedia technologies are developing rapidly. People usually use various images to express information in their work and life, especially color images. Due to the widespread use of color images, their confidentiality is challenged. However, encryption algorithms commonly used in the field of information security, such as AES and RSA, cannot be directly used to achieve the confidentiality of color images. This is because, on the one hand, the amount of color image data is very large, especially the high-resolution color images that are often used now; on the other hand, traditional encryption algorithms are mainly designed for text data, so the encryption algorithms are complex. For example, the DES algorithm requires 16 rounds of iterations, and the AES algorithm requires at least 10 rounds of iterations, while public key algorithms such as RSA are less efficient than DES.

[0003] Since the attractor dimension of the chaotic system is a fractal dimension, it has a very complex fractal structure and good unpredictability. The chaotic system is extremely sensitive to initial conditions and parameters, so the chaotic system can be used in the field of data confidentiality. The existing chaos-based image confidentiality technology usually encrypts the image on the basis of chaotic mapping. For example, the patent with announcement number CN108234813A discloses a "plaintext associated image encryption algorithm based on hyperchaotic Chen system". This method generates four pseudo-random sequence matrices through the Chen chaotic system, and then performs forward diffusion, scrambling and reverse diffusion operations on the plaintext image to obtain the final ciphertext image. Although this method solves the problem of small key space of the Logistic chaotic system, the process is complicated, which is not conducive to image encryption. Generally speaking, the problems existing in the prior art are: the algorithm is relatively complex, resulting in low efficiency and very time-consuming when encrypting and decrypting images, especially for color image encryption; the security of the algorithm needs to be further improved. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a color image encryption method based on Logistic dual-pixel rectangular mapping. On the basis of the chaotic system, a rectangular mapping function is constructed, which well balances the relationship between algorithm complexity and security.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A color image encryption method based on Logistic double-pixel rectangle mapping includes the following steps:

[0007] Step 101: According to the seed key k=(k 1 ,k 2 ) 1 Construct color key image I K ;

[0008] Step 102: Read the plain text color image I P Convert to RGB color space and further separate into R, G, B channels to obtain three plaintext sub-images

[0009] Step 103: According to k 2 , and use the Logistic chaotic system to perturb the three plaintext sub-images obtained in step 102 to obtain

[0010] Step 104: Sub-image obtained in step 103 Perform rectangular mapping operations respectively to obtain their respective ciphertext sub-images

[0011] Step 105: The three ciphertext sub-images obtained in step 104 are Synthesized into the final ciphertext image I C .

[0012] As a preferred solution, in step 101, a color key image I is constructed according to the seed key. K The seed key is composed of an integer between 0 and 255, and its length is variable, with a maximum of 256 bits, equivalent to 2048 bits. The constructed key image I K It is expressed in RGB space as

[0013] As a preferred solution, in step 102, the input plain text color image is represented by using the RGB color model to obtain three component sub-images.

[0014] As a preferred solution, the Logistic chaotic system mathematical model used in step 103 is as follows:

[0015] x k+1 =μx k (1-x k ) (1)

[0016] Among them, x k , x k+1 ∈(0, 1), μ∈(0, 4] when 3.5699456<μ<4, the system enters a chaotic state.

[0017] As a preferred solution, in step 104, the plaintext sub-image Take two pixels as a group and input them into the rectangular function f to obtain three ciphertext sub-images respectively. The rectangular function f is defined as:

[0018]

[0019] Among them, row and col represent the row and column numbers of the pixel pix respectively; L and U represent the pixels immediately to the left and above the pixel respectively.

[0020] As a preferred solution, in step 105, the three ciphertext sub-images are synthesized into an image of one channel using an RGB model to obtain a final ciphertext image.

[0021] As a preferred solution, the decryption algorithm is the inverse process of the encryption algorithm.

[0022] In summary, the present invention has the following beneficial effects:

[0023] 1. The color image encryption method based on Logistic dual-pixel rectangular mapping provided by the present invention can quickly complete the encryption and decryption of various color images. The encrypted ciphertext image destroys the structure of the plaintext image and can effectively resist image pixel frequency statistical attacks;

[0024] 2. The color image encryption method based on Logistic dual-pixel rectangular mapping provided by the present invention has high encryption efficiency, strong practicality, can effectively resist frequency statistical attacks and chosen plaintext attacks, and has good encryption effect. The present invention can be applied to the generation, storage, transmission and other scenarios of color images to effectively protect their confidentiality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the encryption process in an embodiment of the present invention;

[0026] Figure 2 It is a structural schematic diagram of the decryption process in an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of scanning a key image structure in an embodiment of the present invention;

[0028] Figure 4 This is an encryption effect diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] This specification and the claims do not use the difference in names as a way to distinguish components, but rather use the difference in functions of components as the criterion for distinction. As mentioned throughout the specification and the claims, "comprising" is an open-ended term and should be interpreted as "comprising but not limited to". "Substantially" means within an acceptable error range, and those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings, but it is not a limitation to this application.

[0031] First, construct a color key image I according to the seed key K , the seed of which is composed of integers between 0 and 255, and its length is variable, with a maximum of 256, which is equivalent to 2048 bits long; the constructed key image I K can be expressed in the RGB space as

[0032] wherein, the color key image I K is constructed as follows:

[0033] 1. Input the initial value of chaos;

[0034] 2. Use the Logistic chaos system to generate a sequence L1 of size l (0 < l < 256);

[0035] 3. Multiply each value of the sequence obtained from the chaos system by 1000 and then take the modulus of 256 to obtain L2;

[0036] 4. Fill L2 into a 16 * 16 matrix in the Figure 3 scanning order, skip writing repeated numbers, and fill the remaining part in ascending order according to Figure 3 until the entire matrix is filled to obtain a key image I of size 16 * 16 K .

[0037] The construction principle of the color key image I K is: The key is a 16-order square matrix composed of 256 grayscale pixels. I K is derived depending on the seed key k1, repeated numbers are skipped from writing, and the remaining part is filled in ascending order of pixels in turn.

[0038] Then start the image encryption process, convert the read plaintext color image I P into the RGB color space, represent the input plaintext color image using the RGB color model, and further separate it into the R, G, B channels to obtain three plaintext sub-images

[0039] Then according to k2 , and use the Logistic chaotic system to perturb the three plaintext sub-images obtained in step 102 to obtain The mathematical model of the Logistic chaotic system is as follows:

[0040] x k+1 =μx k (1-x k ) (1)

[0041] Among them, x k ,x k+1 ∈(0,1), μ∈(0,4] when 3.5699456<μ<4, the system enters a chaotic state.

[0042] At the same time, for the plaintext sub-image Take two pixels as a group, input them into the rectangular function f, perform rectangular mapping operations respectively, and obtain their respective ciphertext sub-images The rectangular function f is defined as:

[0043]

[0044] Among them, row and col represent the row and column numbers of the pixel pix respectively; L and U represent the pixels immediately to the left and above the pixel respectively.

[0045] Finally, the three ciphertext sub-images are converted into the three ciphertext sub-images using the RGB model. Synthesize into one channel image to get the final ciphertext image I C .

[0046] The above methods (algorithms) are all reversible, and the decryption algorithm is the inverse process of the above encryption algorithm.

[0047] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A color image encryption method based on Logistic double-pixel rectangle mapping, It is characterized in that The following steps are involved: Step 101: According to the seed key k=(k 1 , k 2 ) 1 Construct color key image U K ; Step 102: Read the plain text color image U P Convert to RGB color space and further separate into R, G, B channels to obtain three plaintext sub-images Step 103: According to k 2 , and use the Logistic chaotic system to perturb the three plaintext sub-images obtained in step 102 to obtain Step 104: Sub-image obtained in step 103 Perform rectangular mapping operations respectively to obtain their respective ciphertext sub-images Step 105: The three ciphertext sub-images obtained in step 104 are Synthesized into the final ciphertext image I C ; In step 101, a color key image I is constructed according to the seed key. K The seed key is composed of an integer between 0 and 255, and its length is variable, with a maximum of 256. The constructed key image I K It is expressed in RGB space as The mathematical model of the Logistic chaotic system used in step 103 is as follows: x k+1 =μx k (1-x k ) (1) Among them, x k , x k+1 ∈(0, 1), μ∈(0, 4] When 3.5699456<μ<4, the system enters a chaotic state; In step 104, the plaintext sub-image Take two pixels as a group and input them into the rectangular function f to obtain three ciphertext sub-images respectively. The rectangular function f is defined as: Among them, row and col represent the row and column numbers of the pixel pix respectively; L and U represent the pixels immediately to the left and above the pixel respectively.

2. According to claim 1, the color image encryption method based on Logistic double-pixel rectangular mapping, It is characterized in that In step 102, the input plain text color image is represented by using the RGB color model to obtain three component sub-images.

3. According to the color image encryption method based on Logistic double pixel rectangle mapping described in claim 1, It is characterized in that In step 105, the three ciphertext sub-images are synthesized into an image of one channel using an RGB model to obtain a final ciphertext image.

4. According to the color image encryption method based on Logistic double pixel rectangle mapping described in claim 1, It is characterized in that The decryption algorithm is the reverse process of the encryption algorithm.

Images