Sum-preserving encryption method for image thumbnail

Abstract

An image thumbnail sum preservation encryption method uses a chaotic sequence generator to generate chaotic sequences that rearrange the sub-pixels of sub-blocks to increase confusion and reduce the correlation between pixels. Each rearranged sub-pixel is divided into pixel groups in units of multiple pixels. A chaotic key is generated from the chaotic sequence corresponding to the sub-pixels of each pixel group. The generated chaotic key is used to maintain the preservation replacement of each pixel group, thereby maintaining the image's recognizability at low resolution. This method can significantly increase the difficulty of analyzing encrypted thumbnails and preserve the image's usability.

Claims

1. A sum-preserving encryption method for image thumbnails, comprising: a computing device receiving an input image; the computing device dividing the input image into a plurality of non-overlapping sub-blocks, each sub-block having a plurality of sub-pixels; a chaotic sequence generator of the computing device generating a chaotic sequence, and the computing device rearranging the sub-pixels of each sub-block using the chaotic sequence; the computing device grouping the rearranged sub-pixels of each sub-block into a plurality of pixel groups, each group consisting of a plurality of non-overlapping sub-pixels, and the computing device quantizing and combining a plurality of pseudo-random numbers from the chaotic sequence corresponding to each pixel group to generate a chaotic key corresponding to each pixel group; and a sum-preserving method of the computing device. The substitution module uses a plurality of encryption equations and the chaotic key corresponding to each pixel group to maintain the substitution of each pixel group to generate a plurality of substitution pixel groups, wherein each sub-pixel of each pixel group has a pixel value, each sub-pixel of each substitution pixel group has a substitution pixel value, and the sum of the pixel values ​​of each sub-pixel of each pixel group is the same as the sum of the substitution pixel values ​​of each sub-pixel of each substitution pixel group.

2. The image thumbnail sum of request item 1 is kept encrypted, wherein each sub-block has B×B sub-pixels, where B is a power of 2.

3. The image thumbnail sum of request item 1 or 2 is kept encrypted, wherein the number of pseudo-random numbers in the chaotic sequence generated by the chaotic sequence generator is the same as the number of sub-pixels in each sub-block.

4. The image thumbnail sum preservation encryption method as described in request item 3, wherein the computing device maps each of the pseudo-random numbers to each of the sub-pixels of each of the sub-blocks, and then the computing device rearranges each of the sub-pixels of each of the sub-blocks according to the magnitude of the pseudo-random numbers.

5. As in the image thumbnail sum encryption method of request item 3, the number of sub-pixels in each pixel group is not less than 2, and the chaotic key corresponding to each pixel group is generated by multiplying the pseudo-random numbers corresponding to each pixel group by a magnification ratio, taking the modulus of 256, and then merging them.

6. The image thumbnail summation encryption method as described in Request 1, wherein the chaotic sequence generator receives a plurality of initial parameters for initialization before generating the chaotic sequence, the initial parameters including a chaotic mapping initial value, a chaotic mapping control parameter and an iteration offset value, and the chaotic sequence generator generates the chaotic sequence based on the chaotic mapping initial value, the chaotic mapping control parameter and the iteration offset value.

7. As in Request 6, the method for maintaining the encryption of the sum of image thumbnails, wherein the iterative calculation formula for generating the chaotic sequence by the chaotic sequence generator can be expressed as: , , where, is the initial value of the chaotic mapping, is the pseudo-random number of the chaotic sequence, and is the control parameter of the chaotic mapping.

8. The image thumbnail sum preservation encryption method as described in Request 1, wherein the preservation replacement module divides the encryption equation into multiple arrays based on the sum of the pixel values ​​of each sub-pixel of each pixel group, and performs preservation replacement on each pixel group using the encryption equation of each group respectively.

9. The image thumbnail sum preservation encryption method of claim 8, wherein when the sum of the pixel values ​​of the sub-pixels of each pixel group is between 0 and 254, it is preserved and replaced by a first set of encryption equations; when the sum of the pixel values ​​of the sub-pixels of each pixel group is between 255 and 510, it is preserved and replaced by a second set of encryption equations; and when the sum of the pixel values ​​of the sub-pixels of each pixel group is between 511 and 765, it is preserved and replaced by a third set of encryption equations.

10. As in request item 9, the sum of image thumbnails is kept encrypted, wherein the encryption equation for the first group is: , , , , , where, , respectively, are the pixel values ​​of the sub-pixels of each pixel group, respectively, are the replacement pixel values ​​of the sub-pixels of each replacement pixel group, are the chaotic key of each pixel group, and are the modulus; The encryption equation of the second group is: , , , if, if, if, if, , The encryption equation of the third group is: , , , , .

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