A reversible secret image sharing method and system based on palette image

Abstract

The present invention provides a reversible secret image sharing method and system based on palette images, belonging to the field of image encryption technology. The reversible secret image sharing method comprises: obtaining a grayscale secret image and n palette carrier images and index values ​​of each pixel on each palette carrier image; setting a serial number corresponding to each shadow image when the grayscale secret image is shared; screening and sharing each pixel on the grayscale secret image to determine the pixel value of each shadow pixel on the n shadow images; merging the pixel values ​​of all shadow pixels on each shadow image to obtain n shadow images. The present invention reduces bandwidth load while achieving understandable shadow images and lossless recovery of carrier images.

Description

Technical Field

[0001] The present invention belongs to the technical field of image encryption, and in particular relates to a reversible secret image sharing method and system based on palette images. Background Art

[0002] Secret image sharing generally includes two stages, secret sharing and secret recovery. Secret sharing is participated by multiple participants. The encryption party divides the secret into multiple shadow images that are invisible to the secret information through a certain sharing algorithm, and gives them to the corresponding participants for storage. If you want to recover the secret information, you need to obtain a set of shadow images that meet the recovery conditions. The secret information cannot be effectively recovered by a set of shadow images that do not meet the recovery conditions. In the secret image sharing with a (k, n) threshold, the secret image can only be recovered when k or more shadow images are obtained. No secret information can be obtained with less than k shadow images. These permission control and loss tolerance characteristics that are different from ordinary image encryption methods can be used to ensure the security of secret image storage and transmission processes. The principle of polynomial secret sharing is: in the polynomial secret sharing with a (k, n) threshold, first construct a (k-1)-order polynomial on the number field P:

[0003] f(x)=a0+a1x+…+a k-1 x k-1 (modP);

[0004] In the sharing phase, let the currently processed pixel value s of the secret image be equal to the polynomial constant term a0. The coefficients a1, a2, ..., a k-1 Take a random value on [0,P), x can generally be the sequence number i of the i-th participant, and substitute it into the formula to get the shadow pixel value SC i =f(x i ), replace the serial number x i and f(x i ) is sent to the i-th participant as a sharing pair. When all secret pixels are shared, n shadow images can be obtained.

[0005] In the recovery phase, for the pixel value s that needs to be restored, when any k of the n sharing pairs are obtained, the k coefficients can be solved according to the Lagrange interpolation theorem. The constant term a0 is the restored secret pixel value. If there are less than k sharing values, the solution will be infinite and no secret information will be obtained.

[0006] For polynomial secret sharing, the coefficients a1, a2, ..., a k-1 is a random value on [0,P). Different random values ​​can get different sharing values. Therefore, the coefficients a1, a2, ..., a k-1It can be used as a random element in the sharing process to filter the generated sharing values.

[0007] The carrier reversible secret image sharing method (RSIS) generally has two characteristics: first, the shadow image is understandable, and the generated shadow image is not a noise-like image, but a natural image similar to the carrier image. Second, in the decryption stage, the carrier image can be restored to a certain extent through the shadow image.

[0008] Shadow image understandable secret sharing scheme (MSIS) refers to a type of secret image sharing scheme that can share meaningful shadow images. If the shadow image has the understandability of a natural image, it can avoid being tampered or intercepted by attackers to a certain extent, and it is also convenient for participants to store and manage the shadow image, thereby increasing the security of the shadow image and secret information.

[0009] After recovering the secret image, the reversible secret image sharing method can also use the shadow image to losslessly restore the carrier image. In general secret image sharing, the carrier image cannot be losslessly restored through the shadow image. In some special application scenarios, such as legal evidence, medical diagnostic images, military remote sensing images and other sensitive images, a small change in each pixel will have a great impact on the credibility of the image, and these images are difficult to obtain, the cost of image acquisition is relatively high, and many images cannot be obtained repeatedly. Therefore, in these usage scenarios, it is required that the carrier image can be restored losslessly without distortion.

[0010] At present, the RSIS scheme is based on the carrier being a binary image or a method combined with information hiding. Binary images use 0 and 1 to represent black and white pixels, and the visual quality is relatively poor, and they cannot accurately describe the detailed features of the image. When the carrier is a grayscale image, it is mostly combined with information hiding technology, and only one carrier image is used. The generated shadow images look the same, which is not conducive to the management of shadow images. The information hiding method is limited by the embedding capacity, and the shadow image often has pixel expansion, which increases the bandwidth burden. Summary of the invention

[0011] One of the purposes of the present invention is to provide a reversible secret image sharing method based on palette images, which reduces bandwidth load while achieving understandable shadow images and lossless recovery of carrier images.

[0012] A second objective of the present invention is to provide a reversible secret image sharing system based on palette images.

[0013] A third object of the present invention is to provide an electronic device.

[0014] A fourth object of the present invention is to provide a computer-readable storage medium.

[0015] To achieve one of the above objects, the present invention is implemented by the following technical solutions:

[0016] A reversible secret image sharing method based on a palette image, the reversible secret image sharing method comprising:

[0017] Step S1, obtaining 1 grayscale secret image, n palette carrier images, and the index values of each pixel point on each palette carrier image;

[0018] The index value is the high-order bit value corresponding to the pixel value of each pixel point;

[0019] Step S2, setting the serial number corresponding to each shadow image when sharing the grayscale secret image;

[0020] Step S3, screening and sharing each pixel point on the grayscale secret image according to the index values and serial numbers of each pixel point of the n palette carrier images to determine the pixel values of each shadow pixel point on the n shadow images;

[0021] Step S4, merging the pixel values of all shadow pixel points on each shadow image to obtain n shadow images.

[0022] Further, the reversible secret image sharing method further comprises:

[0023] Step S5, obtaining the pixel values of each shadow pixel point on the n shadow images;

[0024] Step S6, performing binary conversion on the pixel values of each shadow pixel point on the n shadow images to extract the high-order bit values corresponding to each shadow pixel point on each shadow image;

[0025] Step S7, using the high-order bit values corresponding to each shadow pixel point as the index values of the corresponding pixel points on the corresponding palette carrier image to restore the pixel values of the corresponding pixel points on each palette carrier image.

[0026] Further, the high-order bit value is the high four-bit value.

[0027] Further, in step S3, the specific process of the screening and sharing includes:

[0028] Step S31, setting the minimum number k of shadow images required to restore the grayscale secret image;

[0029] (n + 2) / 2 < k ≤ n, k is a positive integer;

[0030] Step S32, setting the initial value of the position number t of the pixel point on the grayscale secret image to 1;

[0031] Step S33, setting a number field [0, P) to randomly generate k-1 random values ​​on the number field [0, P);

[0032] Step S34, calculating n sharing values ​​corresponding to the pixel at position t on the grayscale secret image according to the pixel value of each pixel on the grayscale secret image, the random value and the serial numbers corresponding to the n shadow images;

[0033] Step S35, performing binary conversion on the n shared values ​​corresponding to the pixel point at position t on the grayscale secret image to obtain the high-order bit value of each shared value corresponding to the pixel point at position t;

[0034] Step S36, determining whether the high-order bit value of each shared value corresponding to the pixel point at position t is the same as the index value of the pixel point at position t on the corresponding palette carrier image; if so, taking each shared value corresponding to the pixel point at position t as the pixel value of the shadow pixel point at position t on the corresponding shadow image, and proceeding to step S37; if not, randomly generating k-1 random values ​​again on the number field [0, P), and returning to step S34;

[0035] Step S37, determine whether t is the position number of the last pixel on the grayscale secret image. If so, go to step S4; if not, set t=t+1, and randomly generate k-1 random values ​​again on the number field [0, P), and return to step S34.

[0036] In order to achieve the second objective above, the present invention adopts the following technical solution:

[0037] A reversible secret image sharing system based on a palette image, the reversible secret image sharing system comprising:

[0038] An acquisition module, used to acquire one grayscale secret image and n palette carrier images and the index value of each pixel on each palette carrier image;

[0039] The index value is the high-order bit value corresponding to the pixel value of each pixel point;

[0040] A setting module, used for setting a serial number corresponding to each shadow image when sharing the grayscale secret image;

[0041] A screening and sharing module, for screening and sharing each pixel on the grayscale secret image according to the index value and sequence number of each pixel on the n palette carrier images, so as to determine the pixel value of each shadow pixel on the n shadow images;

[0042] A merging module, which is used to merge the pixel values of all shadow pixel points on each shadow image to obtain n shadow images.

[0043] Furthermore, the reversible secret image sharing system further includes:

[0044] A second acquisition module, which is used to acquire the pixel values of each shadow pixel point on the n shadow images;

[0045] A binary conversion module, which is used to perform binary conversion on the pixel values of each shadow pixel point on the n shadow images to extract the high-order bit values corresponding to each shadow pixel point on each shadow image;

[0046] A restoration module, which is used to use the high-order bit values corresponding to each shadow pixel point as the index values of the corresponding pixel points on the corresponding palette carrier image to restore the pixel values of the corresponding pixel points on each palette carrier image.

[0047] Furthermore, the screening and sharing module includes:

[0048] A first setting sub-module, which is used to set the minimum number k of shadow images required to restore the grayscale secret image;

[0049] (n + 2) / 2 < k ≤ n, where k is a positive integer;

[0050] A second setting sub-module, which is used to set the initial value of the position serial number t of the pixel points on the grayscale secret image to 1;

[0051] A third setting sub-module, which is used to set a number field [0, P) to randomly generate k - 1 random values in the number field [0, P);

[0052] A calculation sub-module, which is used to calculate the n sharing values corresponding to the pixel point at position t on the grayscale secret image according to the pixel values of each pixel point on the grayscale secret image, the random values, and the serial numbers corresponding to the n shadow images;

[0053] A binary conversion sub-module, which is used to perform binary conversion on the n sharing values corresponding to the pixel point at position t on the grayscale secret image respectively to obtain the high-order bit values of each sharing value corresponding to the pixel point at position t;

[0054] The first judgment submodule is used to judge whether the high-order bit value of each shared value corresponding to the pixel point at position t is the same as the index value of the pixel point at position t on the corresponding palette carrier image. If so, each shared value corresponding to the pixel point at position t is used as the pixel value of the shadow pixel point at position t on the corresponding shadow image, and the pixel point t and the pixel value of the shadow pixel point at position t are transmitted to the second judgment submodule; if not, k-1 random values ​​are randomly generated again on the number field [0, P), and transmitted to the calculation submodule;

[0055] The second judgment submodule is used to judge whether t is the position serial number of the last pixel point on the grayscale secret image. If so, the pixel values ​​of all shadow pixels are transmitted to the merging module; if not, t=t+1 is set, and k-1 random values ​​are randomly generated again on the number field [0, P), and transmitted to the calculation submodule.

[0056] In order to achieve the third objective above, the present invention adopts the following technical solution:

[0057] An electronic device, characterized in that the electronic device includes a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the steps in the above-mentioned reversible secret image sharing method are implemented.

[0058] In order to achieve the fourth objective above, the present invention adopts the following technical solution:

[0059] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the above-mentioned reversible secret image sharing method are implemented.

[0060] In summary, the solution proposed by the present invention has the following technical effects:

[0061] The present invention utilizes the index value of each pixel point on n palette carrier images to screen and share each pixel point on the grayscale secret image, while reducing the bandwidth load, ensuring that the high-order bit value of the pixel value of each shadow pixel point on the n shadow images is the same as the index value (i.e., the high-order bit value) of the corresponding pixel point on the corresponding palette carrier image, thereby achieving that the shadow image and the palette carrier image have similar texture and color information, and ensuring that each shadow image is similar and understandable to the corresponding palette carrier image. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0063] Figure 1 It is a schematic diagram of the process of the reversible secret image sharing method based on palette image of the present invention;

[0064] Figure 2 A schematic diagram of the screening and sharing process of each pixel on the grayscale secret image in the present invention;

[0065] Figure 3 Schematic diagram of the 16-color palette image structure. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0067] Palette images are very common on the Internet (such as GIF format), and are often used in medical images, such as X-ray images and magnetic resonance imaging, and can be used as a carrier for information hiding and secret sharing. Palette images can use no more than 256 colors to achieve better visual effects. The palette image file is divided into two parts: one part is the palette, which corresponds to an index value for each color, and the other part is the pixel matrix, which gives the index value of each pixel. For a 16-color palette image, an index value only requires 4 bits, and the index value is the high 4 bits of the actual pixel value, such as Figure 3 The visual quality of a 16-color palette carrier image is similar to a grayscale image, and the storage space required for a palette carrier image is greatly reduced.

[0068] Based on the structural characteristics of the above 16-color palette carrier image, this embodiment provides a reversible secret image sharing method based on the palette image. Figure 1 , the reversible secret image sharing method comprises:

[0069] Step S1, obtaining a grayscale secret image and n palette carrier images and the index value of each pixel on each palette carrier image.

[0070] The grayscale secret image S and the palette carrier image C in this embodiment i have the same size, i=1, 2, ..., n, where n is the number of palette carrier images.

[0071] The palette carrier image in this embodiment is a 16-color palette carrier image. There are 16 index values ​​in the 16-color palette carrier image, corresponding to 8-bit pixel values ​​of 16 colors. The index value of this embodiment is the high-order bit value corresponding to the pixel value of each pixel point, and the high-order bit value is the high-four-bit value. First, according to the pixel value of each pixel point at each position in the 16-color palette carrier image, the index value, that is, the high-four-bit value corresponding to the pixel value of each pixel point at each position is found from the palette (i.e., the index table) of the palette carrier image.

[0072] Step S2: setting a serial number corresponding to each shadow image when sharing the grayscale secret image.

[0073] This embodiment adopts the polynomial secret sharing principle for image sharing, and it is necessary to pre-set the serial number assigned to each shadow image when sharing the grayscale secret image.

[0074] Step S3: Screen and share each pixel on the grayscale secret image according to the index value and serial number of each pixel on the n palette carrier images to determine the pixel value of each shadow pixel on the n shadow images.

[0075] When using random elements for screening, the constraint condition is set that the high 4-bit value of the pixel value of a shadow pixel at a certain position is the same as the high 4-bit value of the pixel value of the corresponding position on the palette carrier image. If the constraint condition is met, the shared value can be retained; otherwise, a random value is reselected and a new shared value is generated again for screening until all values ​​in the secret image are shared, and the generated shadow image is similar to the carrier image and is understandable. The specific process of screening and sharing includes:

[0076] Step S31, setting the minimum number k of shadow images required to restore the grayscale secret image;

[0077] In this embodiment, k is a positive integer and satisfies the following conditions:

[0078] (n+2) / 2 <k≤n。

[0079] Step S32, setting the initial value of the position number t of the pixel point on the grayscale secret image to 1;

[0080] Step S33, setting a number field [0, P) to randomly generate k-1 random values ​​on the number field [0, P);

[0081] Step S34, calculating n sharing values ​​corresponding to the pixel at position t on the grayscale secret image according to the pixel value of each pixel on the grayscale secret image, the random value and the serial numbers corresponding to the n shadow images;

[0082] This embodiment adopts the polynomial secret sharing principle to share, and obtains n sharing values ​​corresponding to the pixel point at position t on the grayscale secret image.

[0083] Step S35, performing binary conversion on the n shared values ​​corresponding to the pixel point at position t on the grayscale secret image to obtain the high-order bit value of each shared value corresponding to the pixel point at position t.

[0084] In this embodiment, the high-order bit value is generally the high four-bit value.

[0085] Step S36, determining whether the high-order bit value of each shared value corresponding to the pixel point at position t is the same as the index value of the pixel point at position t on the corresponding palette carrier image; if so, taking each shared value corresponding to the pixel point at position t as the pixel value of the shadow pixel point at position t on the corresponding shadow image, and proceeding to step S37; if not, randomly generating k-1 random values ​​again on the number field [0, P), and returning to step S34;

[0086] Step S37, determine whether t is the position number of the last pixel on the grayscale secret image. If so, go to step S4; if not, set t=t+1, and randomly generate k-1 random values ​​again on the number field [0, P), and return to step S34.

[0087] Step S4: Merge the pixel values ​​of all shadow pixels on each shadow image to obtain n shadow images.

[0088] This embodiment can realize the understanding of the shadow image and also realize the lossless restoration of the palette carrier image. When the palette carrier image is restored, the i-th shadow image SC i The high bit value of the pixel value of each shadow pixel point in the image is used as the index value (the present embodiment uses the bit value corresponding to the high 4 bits) and the pixel value corresponding to the index value is found from the index table of the palette carrier image, that is, the pixel value of the palette carrier image is restored. The specific implementation process includes:

[0089] Step S5: Obtain the pixel value of each shadow pixel point on the n shadow images.

[0090] Step S6: performing binary conversion on the pixel value of each shadow pixel on the n shadow images to extract the high-order bit value corresponding to each shadow pixel on each shadow image.

[0091] Step S7: Use the high-order bit value corresponding to each shadow pixel point as the index value of the corresponding pixel point on the corresponding palette carrier image to restore the pixel value of the corresponding pixel point on each palette carrier image.

[0092] Sharing stage: (3, 3) When sharing with threshold, the pixel value of the grayscale secret image at position t is 117, and the generated sharing values ​​are 120, 180, and 199. The corresponding pixel values ​​of the pixel at position t in the three palette carrier images are 7, 11, and 12, respectively, which are converted to binary as 0111, 1011, and 1100. When screening, compare whether the upper 4 bits of 120, 180, and 199 are 0111, 1011, and 1100, respectively. If so, the sharing is successful; otherwise, use random values ​​for screening again.

[0093] Restoration stage: Obtain the pixel values ​​of the shadow pixel at position t of the three shadow images, which are 120, 180 and 199 respectively, and extract their high 4 bits, which are 0111, 1011 and 1100, i.e. 7, 11 and 12, respectively, as the index values ​​of the pixel at position t of the corresponding palette carrier image. Then, based on the one-to-one correspondence between the index value and the actual pixel value in the palette, the carrier image can be restored losslessly. When restoring the secret image, obtain the pixel values ​​of the shadow images, which are 120, 180 and 199, and restore the pixel values ​​of the corresponding pixels of the secret image according to the Lagrange interpolation theorem.

[0094] This embodiment uses the index value of each pixel on n palette carrier images to screen and share each pixel on the grayscale secret image. While reducing the bandwidth load, it ensures that the high-order bit value of the pixel value of each shadow pixel on the n shadow images is the same as the index value (i.e., the high-order bit value) of the corresponding pixel on the corresponding palette carrier image, thereby achieving the shadow image and the palette carrier image having similar texture and color information, and ensuring that each shadow image is similar and understandable to the corresponding palette carrier image.

[0095] The above embodiments can be implemented by adopting the technical solutions given in the following embodiments:

[0096] Another embodiment provides a palette image-based reversible secret image sharing system, the reversible secret image sharing system comprising:

[0097] An acquisition module, used to acquire one grayscale secret image and n palette carrier images and the index value of each pixel on each palette carrier image;

[0098] The index value is the high-order bit value corresponding to the pixel value of each pixel point;

[0099] A setting module, used for setting a serial number corresponding to each shadow image when sharing the grayscale secret image;

[0100] A screening and sharing module, which is used to screen and share each pixel point on the grayscale secret image according to the index value and serial number of each pixel point of the n palette carrier images, so as to determine the pixel values of each shadow pixel point on the n shadow images. The screening and sharing module includes:

[0101] A first setting sub-module, which is used to set the minimum number k of shadow images required to restore the grayscale secret image;

[0102] Where (n + 2) / 2 < k ≤ n, and k is a positive integer;

[0103] A second setting sub-module, which is used to set the initial value of the position serial number t of the pixel point on the grayscale secret image to 1;

[0104] A third setting sub-module, which is used to set a number field [0, P), and randomly generate k - 1 random values in the number field [0, P);

[0105] A calculation sub-module, which is used to calculate n sharing values corresponding to the pixel point at position t on the grayscale secret image according to the pixel values of each pixel point on the grayscale secret image, the random values, and the serial numbers corresponding to the n shadow images;

[0106] A binary conversion sub-module, which is used to perform binary conversion on the n sharing values corresponding to the pixel point at position t on the grayscale secret image respectively, so as to obtain the high-order bit values of each sharing value corresponding to the pixel point at position t;

[0107] A first judgment sub-module, which is used to judge whether the high-order bit value of each sharing value corresponding to the pixel point at position t is the same as the index value of the pixel point at position t on the corresponding palette carrier image. If so, each sharing value corresponding to the pixel point at position t is used as the pixel value of the shadow pixel point at position t on the corresponding shadow image, and the pixel point t and the pixel value of the shadow pixel point at position t are transmitted to the second judgment sub-module; if not, k - 1 random values are randomly generated again in the number field [0, P), and are transmitted to the calculation sub-module;

[0108] A second judgment sub-module, which is used to judge whether t is the position serial number of the last pixel point on the grayscale secret image. If so, the pixel values of all shadow pixel points are transmitted to the merging module; if not, let t = t + 1, and randomly generate k - 1 random values again in the number field [0, P), and are transmitted to the calculation sub-module.

[0109] A merging module, which is used to merge the pixel values of all shadow pixel points on each shadow image to obtain n shadow images.

[0110] The reversible secret image sharing system of this embodiment further includes:

[0111] A second acquisition module is used to acquire the pixel value of each shadow pixel point on the n shadow images;

[0112] A binary conversion module, used for performing binary conversion on the pixel value of each shadow pixel point on the n shadow images, so as to extract the high-order bit value corresponding to each shadow pixel point on each shadow image;

[0113] The recovery module is used to use the high-order bit value corresponding to each shadow pixel point as the index value of the corresponding pixel point on the corresponding palette carrier image, so as to recover the pixel value of the corresponding pixel point on each palette carrier image.

[0114] Another embodiment provides an electronic device, which includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps in the reversible secret image sharing method provided in the embodiment are implemented. Among them, the electronic device also includes a communication interface, a display screen and an input device, and the memory, the processor, the communication interface, the display screen and the input device are connected through a system bus. The processor is used to provide computing and control capabilities. The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the electronic device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be implemented through WIFI, an operator network, near field communication (NFC) or other technologies. The display screen of the electronic device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the electronic device can be a touch layer covered on the display screen, or a key, trackball or touchpad provided on the housing of the electronic device, or an external keyboard, touchpad or mouse, etc.

[0115] Still another embodiment provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps in the reversible secret image sharing method provided in the embodiment are implemented.

[0116] Please note that the technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0117] The professional terms and formulas involved in the above embodiments and the definitions of parameters in the formulas are consistent and will not be repeated here.

[0118] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A reversible secret image sharing method based on palette image, characterized in that: The reversible secret image sharing method comprises: Step S1, obtain a grayscale secret image and n palette carrier images and the index value of each pixel on each palette carrier image; The index value is the high-order bit value corresponding to the pixel value of each pixel point; Step S2, setting a serial number corresponding to each shadow image when sharing the grayscale secret image; Step S3: according to the n The index value and serial number of each pixel point of the palette carrier image are screened and shared for each pixel point on the grayscale secret image to determine n The pixel value of each shadow pixel on the shadow image; In step S3, the specific process of screening and sharing includes: Step S31: Setting the minimum number of shadow images required to restore the grayscale secret image k ; The n +2) / 2< k ≤ n , k is a positive integer; Step S32: Setting the position serial number of the pixel point on the grayscale secret image t The initial value of is 1; Step S33: Set a number field [0, P) to randomly generate k -1 random value; Step S34: according to the pixel value, random value and n The sequence number corresponding to the shadow image is calculated on the grayscale secret image. t The pixel position corresponds to n Share value; Step S35: Upload the grayscale secret image t The pixel position corresponds to n The shared values ​​are converted into binary form to obtain the t The high bit value of each shared value corresponding to the position pixel; Step S36: Determine the t The high bit value of each shared value corresponding to the pixel position and the corresponding palette carrier image t Are the index values ​​of the pixel points at the same position the same? If so, t Each shared value corresponding to the position pixel point is used as the corresponding shadow image t If the pixel value of the shadow pixel at the position is not reached, the process proceeds to step S37; if not, a new random value is generated in the number field [0, P). k -1 random value, return to step S34; Step S37: Determination t Is it the position number of the last pixel on the grayscale secret image? If yes, go to step S4; if not, let t = t +1, and re-randomly generate k -1 random value, return to step S34; Step S4: Merge the pixel values ​​of all shadow pixels on each shadow image to obtain n A shadow image.

2. The reversible secret image sharing method according to claim 1, characterized in that: The reversible secret image sharing method further comprises: Step S5: Obtain the n The pixel value of each shadow pixel on the shadow image; Step S6: n The pixel value of each shadow pixel on each shadow image is converted into binary to extract the high-order bit value corresponding to each shadow pixel on each shadow image; Step S7: Use the high-order bit value corresponding to each shadow pixel point as the index value of the corresponding pixel point on the corresponding palette carrier image to restore the pixel value of the corresponding pixel point on each palette carrier image.

3. The reversible secret image sharing method according to claim 1 or 2, characterized in that: The high-order bit value is the high-order four-bit value.

4. A reversible secret image sharing system based on palette images, characterized in that: The reversible secret image sharing system comprises: Acquisition module, used to obtain a grayscale secret image and n palette carrier images and the index value of each pixel on each palette carrier image; The index value is the high-order bit value corresponding to the pixel value of each pixel point; A setting module, used for setting a serial number corresponding to each shadow image when sharing the grayscale secret image; The screening sharing module is used to n The index value and serial number of each pixel point of the palette carrier image are screened and shared for each pixel point on the grayscale secret image to determine n The pixel value of each shadow pixel on the shadow image; The screening and sharing module includes: The first setting submodule is used to set the minimum number of shadow images required to restore the grayscale secret image. k ; The n +2) / 2< k ≤ n , k is a positive integer; The second setting submodule is used to set the position sequence number of the pixel points on the grayscale secret image t The initial value of is 1; The third setting submodule is used to set a number field [0, P) to randomly generate k -1 random value; The calculation submodule is used to calculate the pixel value, random value and n The sequence number corresponding to the shadow image is calculated on the grayscale secret image. t The pixel position corresponds to n Share value; The binary conversion submodule is used to convert the grayscale secret image t The pixel position corresponds to n The shared values ​​are converted into binary form to obtain the t The high bit value of each shared value corresponding to the position pixel; The first judgment submodule is used to judge the t The high bit value of each shared value corresponding to the pixel position and the corresponding palette carrier image t Are the index values ​​of the position pixels the same? If so, then t Each shared value corresponding to the position pixel point is used as the corresponding shadow image t The pixel value of the shadow pixel point is t and the t The pixel value of the shadow pixel at the position is transmitted to the second judgment submodule; if not, a random value is generated again on the number domain [0, P) k -1 random value, and transmit it to the calculation submodule; The second judgment submodule is used to judge t Is it the position number of the last pixel on the grayscale secret image? If so, transmit the pixel values ​​of all shadow pixels to the merging module; if not, let t = t +1, and re-randomly generate k -1 random value, and transmit it to the calculation submodule; The merging module is used to merge the pixel values ​​of all shadow pixels on each shadow image to obtain n A shadow image.

5. The reversible secret image sharing system according to claim 4, characterized in that: The reversible secret image sharing system further comprises: The second acquisition module is used to obtain the n The pixel value of each shadow pixel on the shadow image; A binary conversion module is used to convert the n The pixel value of each shadow pixel on each shadow image is converted into binary to extract the high-order bit value corresponding to each shadow pixel on each shadow image; The recovery module is used to use the high-order bit value corresponding to each shadow pixel point as the index value of the corresponding pixel point on the corresponding palette carrier image, so as to recover the pixel value of the corresponding pixel point on each palette carrier image.

6. An electronic device, characterized in that: The electronic device includes a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the steps in the reversible secret image sharing method described in any one of claims 1 to 3 are implemented.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the reversible secret image sharing method described in any one of claims 1 to 3 are implemented.

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