Image local scrambling method based on tornado transform

Abstract

In many fields, a large number of images are generated every day. In order to protect image information from being stolen and improve the security and efficiency of encryption during network transmission, a tornado transform is designed, and a local image scrambling method based on tornado transform is proposed. First, by using tornado transform, the pixel value of each layer of tornado is converted into a vector in a certain way; secondly, these vectors are randomly cyclically shifted; finally, the results of cyclic shift are placed in the pixel position of each layer of tornado in a certain way to achieve scrambling operation. Experimental results show that this method can achieve effective scrambling of local areas by selecting the region of interest, which improves the security and efficiency of the scrambling process.

Description

Technical Field

[0001] The invention relates to an information encryption technology, in particular to an image local scrambling method. Background Art

[0002] In recent years, people have paid more and more attention to the security issues of networks and information systems, and images have become an important information carrier in people's daily lives. It can convey a large amount of information intuitively and vividly, and is widely used in communications, military and medical fields. However, due to the openness of the Internet, information is easily intercepted or leaked during network transmission. Data hiding and image encryption are common methods to keep images secure, but the former is subject to some limitations due to the lack of sufficiently large embedding capacity. In contrast, image encryption can effectively protect images. Therefore, how to encrypt images effectively and securely becomes very important.

[0003] Because images have large data capacity and high correlation between pixels and data redundancy, traditional data encryption algorithms cannot encrypt digital images. In recent years, various encryption algorithms based on chaos have been proposed, such as chaos-based image encryption, compressed sensing-based image encryption, and genetic algorithm-based image encryption. With the advent of the big data era, network information transmission capabilities have also been improved, and the requirements for the efficiency and security of encryption algorithms have also been further improved.

[0004] In order to protect image information from being stolen and improve the security and efficiency of encryption during network transmission, a local image scrambling method based on tornado transformation is proposed. This method selects the region of interest to achieve effective scrambling of the local area, laying the foundation for further image encryption and improving the security and efficiency of the scrambling process. Summary of the invention

[0005] The purpose of the present invention is to protect image information from being stolen and to improve the security and efficiency of encryption during network transmission. A local image scrambling method based on tornado transformation is proposed.

[0006] Technical solution of the present invention: To achieve the above-mentioned purpose of the invention, the technical solution adopted is a local image scrambling method based on tornado transformation, and the scrambling steps are described in detail as follows:

[0007] Step 1: Select the region of interest in the image: Let the original image be I , whose size is m × n , select by edge computing or manual I Medium rectangular image region of interest C , whose size is s × t ;

[0008] Step 2: Calculation C Number of layers: C The rectangle formed by the outermost pixel values C 1 , called the first layer of a tornado, C The rectangle formed by the pixel values ​​of the second outer layer C 2 , called the second layer of the tornado, ..., layer by layer, until C Central location C k , called the tornado k Layer; the total number of layers in a tornado k for:

[0009] k = min ( ceil (0.5× s ), ceil (0.5× t )), (1)

[0010] in, min (•) is the minimum function, ceil (•) is the ceiling function;

[0011] Step 3: Generate chaotic sequence: Logistic mapping is:

[0012] x n+1 = rx n (1+ x n ), (2)

[0013] in, r ∈[3.57, 4) is the control parameter, x n ∈(0, 1); randomly selected r and initial value x 0, iterate formula (2) k times, we can get a length of k Chaotic sequence L 1 ;

[0014] Step 4: Integerization of chaotic sequence: Use formula (3) to L 1 Integerization,

[0015] L 2 = floor ( mod ( L 1×10 16 , 2×( s + t ))), (3)

[0016] in, mod (•) represents the modulo operation, floor (•) is the floor function, L 2 For a length of k Integer chaotic sequence of ;

[0017] Step 5: Tornado transformation: According to a certain method, the pixel value of each layer of the tornado is converted into a vector, and these vectors are randomly cyclically shifted; then the result of the cyclic shift is placed in the pixel position of each layer of the tornado according to a certain method;

[0018] Step 6: Generate a scrambled image: Use the tornado transform to C i All pixel values ​​are converted into vectors H i ,use L 2 And formula (4) H i Perform random circular shift operations,

[0019] P i = circshift ( H i , L 2 ( i )), i =1, 2, …, k , (4)

[0020] in, L 2 ( i )∈ L 2 , circshift ( H i , L 2 ( i )) is correct H i Cyclic shift L 2 ( i ) bit function, P i is the new vector after circular shift; P i All pixel values ​​in the tornado are placed ini The pixel position of the layer is realized C The scrambling operation can obtain a size of s × t Scrambled image E ;

[0021] Step 7: Generate encrypted image: E replace I In the image region of interest, we can get a size of m × n The encrypted image.

[0022] In the decryption process, the scrambled image is operated using the same chaotic sequence to restore the plaintext image. The decryption process is the inverse process of scrambling.

[0023] Beneficial effects: In order to protect image information from being stolen and improve the security and efficiency of encryption during network transmission, a local image scrambling method based on tornado transform is proposed. The main contributions are: (1) The rectangular image region of interest in the original image is selected by edge computing or manual methods, and the selected region of interest is scrambled in a targeted manner, thereby improving the encryption efficiency; (2) Inspired by the tornado, a tornado transform is designed for image scrambling; (3) Using the tornado transform, a local image scrambling method based on the tornado transform is proposed; (4) Experimental results show that the local image scrambling method based on the tornado transform has achieved good results in terms of visual effect and scrambling degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 : Scrambling flow chart;

[0025] Figure 2 : original image;

[0026] Figure 3 : image region of interest;

[0027] Figure 4 : Encrypted image. DETAILED DESCRIPTION

[0028] The implementation process of the present invention is further described in detail below with reference to specific drawings and examples.

[0029] Figure 1 This is the scrambling flow chart of this method.

[0030] The programming software used is Matlab R2016a, Figure 2 The Couple grayscale image with a size of 512×512 is shown as the experimental object.

[0031] Step 1: Select the region of interest in the image: Let the original image be I , whose size is 512×512, is selected by edge computing or manual I Medium rectangular image region of interest C ,like Figure 3 As shown, its size is 320×200.

[0032] Step 2: Calculation C Number of layers: Use formula (1) to calculate the total number of layers of a tornado k is 100.

[0033] Step 3: Generate a chaotic sequence: Iterate formula (2) 100 times to obtain a chaotic sequence with a length of 100. L 1 .

[0034] Step 4: Integerization of chaotic sequence: Use formula (3) to L 1 Integerization can give an integer chaotic sequence with a length of 100. L 2 .

[0035] Step 5: Tornado transformation: According to a certain method, the pixel value of each layer of the tornado is converted into a vector, and these vectors are randomly circularly shifted; then the results of the circular shift are placed in the pixel position of each layer of the tornado according to a certain method.

[0036] Step 6: Generate a scrambled image: Use the tornado transform to C i All pixel values ​​are converted into vectors H i ,use L 2 And formula (4) H i Perform random circular shift operations, P i is the new vector after circular shift; P i All pixel values ​​in the tornado are placed in i The pixel position of the layer is realized C The scrambling operation can get a scrambled image of size 320×200 E .

[0037] Step 7: Generate encrypted image: E replace I The image area of ​​interest in , we can get an encrypted image of size 512 × 512, such as Figure 4 shown.

[0038] During the decryption process, the same chaotic sequence is used to scramble the image. E The original image can be restored by decryption operation, and the decryption process is the reverse process of scrambling.

Claims

1. The local image scrambling method based on tornado transformation is characterized by: The scrambling process includes the following steps: Step 1: Select the region of interest in the image: Let the original image be I , whose size is m × n , using edge computing or manual selection I Medium rectangular image region of interest C , whose size is s × t ; Step 2: Calculation C Number of layers: C The rectangle formed by the outermost pixel values C 1 , called the first layer of a tornado, C The rectangle formed by the pixel values ​​of the second outer layer C 2 , called the second layer of the tornado, ..., layer by layer, until C Central location C k , called the tornado k Layer; the total number of layers in a tornado k for: k = min ( ceil (0.5× s ), ceil (0.5× t ))， （1） in, min (•) is the minimum function, ceil (•) is the ceiling function; Step 3: Generate chaotic sequence: Logistic mapping is: x n+1 = rx n (1+ x n ）， （2） in, r ∈[3.57, 4) is the control parameter, x n ∈(0, 1); randomly selected r and initial value x 0, iterate formula (2) k times, we can get a length of k Chaotic sequence L 1 ; Step 4: Integerization of chaotic sequence: Use formula (3) to L 1 Integerization, L 2 = floor ( mod ( L 1 ×10 16 , 2×( s + t )))， （3） in, mod (•) represents the modulo operation, floor (•) is the floor function, L 2 For a length of k Integer chaotic sequence of ; Step 5: Tornado transformation: According to a certain method, the pixel value of each layer of the tornado is converted into a vector, and these vectors are randomly cyclically shifted; then the result of the cyclic shift is placed in the pixel position of each layer of the tornado according to a certain method; Step 6: Generate a scrambled image: Use the tornado transform to C i All pixel values ​​are converted into vectors H i ,use L 2 And formula (4) H i Perform random circular shift operations, P i = circshift ( H i , L 2 ( i ))， i =1, 2, …, k ， （4） in, L 2 ( i )∈ L 2 , circshift ( H i , L 2 ( i )) is correct H i Cyclic shift L 2 ( i ) bit function, P i is the new vector after circular shift; P i All pixel values ​​in the tornado are placed in i The pixel position of the layer is realized C The scrambling operation can obtain a size of s × t Scrambled image E ; Step 7: Generate encrypted image: E replace I In the image region of interest, we can get a size of m × n The encrypted image.

Images