JPEG thumbnail protection method and system based on Galois field polynomial secret sharing

Abstract

The invention relates to a JPEG thumbnail protection method and system based on Galois field polynomial secret sharing. The method comprises the following steps: firstly, an image owner performs a series of processing on an image, including color space conversion, sampling, blocking, discrete cosine transform and quantization, so as to obtain a quantization coefficient matrix; thirdly, performing differential coding and run length coding on the matrix, and setting modifications of a direct-current coefficient and an alternating-current coefficient; secondly, extracting a binary bit of the direct current coefficient difference value, mapping the binary bit into a Galois field number, performing polynomial secret sharing, generating an encrypted direct current mapping value, and converting the encrypted direct current mapping value into an encrypted direct current coefficient two-tuple; meanwhile, binary bits of non-zero values of the alternating current coefficients are extracted and mapped into Galois field numbers, polynomial secret sharing is carried out, encrypted alternating current mapping values are generated, and the encrypted alternating current mapping values are converted into encrypted alternating current coefficient triples. And finally, combining the encrypted direct-current coefficient two-tuple with the alternating-current coefficient three-tuple, generating a plurality of encrypted JPEG images, and uploading the JPEG images to the cloud. According to the method, selective encryption is adopted, data privacy is protected, basic visual features of the image are reserved, the thumbnail is effectively prevented from being maliciously stolen or abused, a user can conveniently and rapidly recognize image content, and good balance between data safety and practicability is achieved.

Description

Technical Field

[0001] The present invention relates to JPEG thumbnail encryption protection technology, belonging to the fields of image privacy protection and information security. Specifically, the present invention combines Galois field polynomial secret sharing and JPEG compression characteristics to achieve secure encryption and protection of JPEG image thumbnails stored in the cloud. This method is applicable to the encryption protection of JPEG image thumbnails in a cloud storage environment, especially suitable for scenarios with high requirements for image privacy, such as the secure storage and sharing of medical images, financial archives, and personal data. Background Art

[0002] With the rapid development of cloud computing and cloud storage technologies, more and more users choose to upload their data to the cloud. However, data privacy and security issues in the cloud storage environment have attracted increasing attention. Especially for scenarios involving sensitive information (such as medical images, financial archives, and personal data), how to ensure data security while meeting users' usage requirements has become an important research topic.

[0003] Due to its efficient compression algorithm, JPEG images are widely used in image storage and transmission. In a cloud environment, to improve data access efficiency, the server usually generates thumbnails of images for users to preview. However, directly storing the thumbnails may disclose the image content of users, thus bringing privacy risks. In response to this problem, thumbnail encryption technology has emerged. It not only needs to ensure data security but also retain the browsability of the images to a certain extent to meet the normal usage requirements of users. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a JPEG thumbnail protection method and system method based on Galois field polynomial secret sharing.

[0005] The technical solution steps of the present invention are as follows:

[0006] In a first aspect, the present invention provides a JPEG thumbnail protection method based on Galois field polynomial secret sharing, which is used to support the generation of encrypted thumbnails with a certain degree of browsability while protecting the privacy of JPEG images. By combining Galois field operations and JPEG compression characteristics, this method can effectively perform selective encryption on the direct current coefficients and alternating current coefficients of images, ensuring data security while retaining the basic visual information of the images. It includes:

[0007] S1. The image owner converts the color image to the YCbCr color space, and performs downsampling, pixel block division, discrete cosine transform, and quantization processing to obtain the quantization coefficient matrix of each pixel block;

[0008] S2. The image owner converts the quantization coefficient matrix of each pixel block into a one-dimensional sequence, with the first element of the sequence being the DC coefficient and the remaining elements being the AC coefficients. Then, differential coding is performed on the DC coefficients of all sequences to obtain the difference between each DC coefficient and the previous one, and run-length coding is performed on the AC coefficients of all sequences;

[0009] S3. The image owner sets the modification amounts for the DC coefficients and the AC coefficients;

[0010] S4. The image owner extracts the binary bits of the difference of each DC coefficient according to the DC coefficient modification amount and maps them to the corresponding Galois field numbers;

[0011] S5. The image owner performs polynomial secret sharing on the mapped values of each DC coefficient in the corresponding Galois field to generate multiple encrypted DC mapped values and converts them into multiple encrypted DC coefficient binary tuples;

[0012] S6. The image owner extracts the binary bits of its non-zero values according to the AC coefficient modification amount and maps them to the corresponding Galois field numbers;

[0013] S7. The image owner performs polynomial secret sharing on the mapped values of the AC coefficients in the corresponding Galois field to generate multiple encrypted AC mapped values and converts them into multiple encrypted AC coefficient triples;

[0014] S8. The image owner combines the multiple generated encrypted DC coefficient binary tuples and AC coefficient triples respectively to generate multiple encrypted JPEG images and uploads them to the cloud.

[0015] Preferably, as in the first aspect above, the specific method of S2 is as follows:

[0016] S21. The image owner performs a zigzag scan on the quantization coefficient matrix of each pixel block to convert the two-dimensional matrix into a one-dimensional sequence, where the first element of each sequence is the DC coefficient and the remaining elements are the AC coefficients;

[0017] S22. Differential coding is performed on the DC coefficients of all sequences to calculate the difference between each DC coefficient and the previous one, and it is represented by a binary tuple [ds p , the binary representation dv p composed of; p / dv p ;

[0018] S23. Run-length coding is performed on the AC coefficients of all sequences, and each non-zero AC coefficient is recorded as the number r q of consecutive zero values before this non-zero coefficient, the binary number of bits s of this non-zero coefficientq , the binary representation v of the non-zero coefficient q to form a triple [(r q , s q ) / v q .

[0019] As a preference of the above first aspect, the specific method of S4 is as follows:

[0020] S41. The image owner extracts the binary bits of the difference of the DC coefficient from the binary representation dv of the difference of each DC coefficient according to the smaller of the modification amount α of the DC coefficient and the number of binary digits ds p therein; where when α ≤ ds p , the lowest α binary bits are extracted, and when α > ds p , the lowest ds p binary bits are extracted; p

[0021] S42. Map the binary bits extracted in S41 to the corresponding Galois field numbers, denoted as the DC mapping number a 0 .

[0022] As a preference of the above first aspect, the specific method of S5 is as follows:

[0023] S51. The image owner constructs a (k - 1)-order polynomial f(x) on the corresponding Galois field with the DC mapping number a 0 of each DC coefficient as the base and k - 1 numbers randomly selected in the Galois field as the coefficients;

[0024] S52. Select n different identity numbers x 1 , x 2 , …, x n and input them into the polynomial f(x) respectively to obtain n encrypted DC mapping values f(x 1 ), f(x 2 ), …, f(x n );

[0025] S53. Fill the n encrypted DC mapping values f(x 1 ), f(x 2 ), …, f(x n ) into the binary bits of the difference respectively to generate n encrypted binary groups; where if α binary bits are extracted in S41, each DC mapping value is filled into the lowest α bits, and if ds p binary bits are extracted in S41, each DC mapping value is filled into the lowest ds p bits;

[0026] ​S54. Verify whether the differences corresponding to the generated n encrypted binary tuples all satisfy that their DC coefficients are within the range where Q 00 is the quantization coefficient of the quantization table at the coordinate (0, 0); if any binary tuple does not meet the condition, randomly select another set of coefficients of the polynomial f(x) and repeat the above steps S52 and S53 until all the generated n encrypted binary tuples meet the condition.

[0027] As an optimization of the above first aspect, the specific method of S6 is as follows:

[0028] S61. The image owner extracts the binary bits of the non-zero AC coefficients according to the modification amount β of the AC coefficients; when β ≤ s q , extract its lowest β binary bits, and when β > s q , extract its lowest s q binary bits;

[0029] S62. Map the binary bits extracted in S61 to the corresponding Galois field numbers, denoted as the AC mapping number b 0 ;

[0030] As an optimization of the above first aspect, the specific method of S7 is as follows:

[0031] S71. The image owner constructs a (k - 1)-order polynomial g(x) on the corresponding Galois field with the AC mapping number b 0 of each non-zero AC coefficient as the base and k - 1 numbers randomly selected in the Galois field as the coefficients;

[0032] S72. Select n different identity numbers x 1 , x 2 , …, x n and input them into the polynomial g(x) to obtain n encrypted AC mapping values g(x 1 ), g(x 2 ), …, g(x n );

[0033] S73. Fill the n encrypted AC mapping values g(x 1 ), g(x 2 ), …, g(x n ) into the non-zero coefficient binary bits respectively to generate n encrypted triples; where if β binary bits are extracted in S61, fill the lowest β bits, and if s q binary bits are extracted in S61, fill the lowest s q bits.

[0034] As an optimization of the above first aspect, the specific method of S8 is as follows:

[0035] S81. The image owner generates n encrypted JPEG images based on the identity numbers x 1 , x 2 , …, x n , in combination with the encrypted binary pairs and encrypted ternary pairs corresponding to each identity number;

[0036] S82. Distribute the n encrypted JPEG images, the n identity numbers, the modification amounts α, β, and n and k to n receivers respectively, where each receiver obtains one encrypted JPEG image, one identity number, the modification amounts α, β, and n and k.

[0037] In a second aspect, the present invention provides a JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing. After n receivers respectively receive one encrypted JPEG image, one identity number, the modification amounts α, β, and n and k generated by the JPEG thumbnail protection encryption method described in any item of the first aspect above, the method for any k receivers to perform image decryption by combining all their encrypted JPEG images and identity numbers is as follows:

[0038] S91. Any k participants pool all their k encrypted JPEG images to obtain k sets of DC coefficients and AC coefficients;

[0039] S92. Convert the k sets of DC coefficients and AC coefficients into encrypted DC binary pairs and AC ternary pairs respectively;

[0040] S93. Extract k encrypted difference binary bits at corresponding positions according to the DC modification amount α; specifically, when α ≤ ds p , extract its lowest α binary bits, and when α > ds p , extract its lowest ds p binary bits;

[0041] S94. Map the k extracted encrypted binary bits to the corresponding Galois field numbers f(x 1 ), f(x 2 ), …, f(x k ); specifically, when α ≤ ds p , map it to a number in the Galois field GF(2 α ), and when α > ds p , map it to a number in the Galois field ;

[0042] S95. Obtain k encrypted difference binary bits f(x 1 ), f(x 2 ), …, f(x kAfter that, reconstruct the DC mapping number α through the Lagrange interpolation polynomial 0 , and fill it into the binary tuple, where

[0043] S96. Repeat steps S93 - S95 until all encrypted DC coefficients at all positions are processed.

[0044] S97. Extract the k encrypted non - zero coefficient binary bits at the corresponding position according to the DC modification amount β; specifically, when β ≤ s q , extract its lowest β binary bits, and when β > s q , extract its lowest s q binary bits;

[0045] S98. Map the extracted k encrypted non - zero coefficient binary bits to the corresponding Galois field numbers g(x 1 ), g(x 2 ), …, g(x k ); specifically, when β ≤ s q , map it to a number in the Galois field GF(2 β ), and when β > s q , map it to a number in the Galois field ;

[0046] S99. After obtaining the k encrypted non - zero coefficient binary bits g(x 1 ), g(x 2 ), …, g(x k ), reconstruct the DC mapping number b through the Lagrange interpolation polynomial 0 , and fill it into the triple, where

[0047] S910. Repeat steps S97 - S99 until all encrypted AC coefficients at all positions are processed.

[0048] S911. Combine the obtained DC coefficients and AC coefficients to obtain the original JPEG image.

[0049] In a third aspect, the present invention provides an encryption - decryption system for JPEG thumbnail protection based on Galois field polynomial secret sharing, which includes:

[0050] An encryption system, which is used to generate an encrypted JPEG image according to the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing described in any item of the first aspect above and save it in the cloud;

[0051] A decryption system is used to decrypt an encrypted JPEG image according to the JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing described in the second aspect above.

[0052] In a fourth aspect, the present invention provides a computer-readable storage medium, characterized in that a computer program is stored on the storage medium, and when the computer program is executed by a processor, it can implement the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing described in any item of the first aspect above, or implement the JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing described in the second aspect above.

[0053] In a fifth aspect, the present invention provides a computer electronic device, characterized in that it includes a memory and a processor;

[0054] The memory is used to store a computer program;

[0055] The processor is used to, when executing the computer program, implement the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing described in any item of the first aspect above, or implement the JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing described in the second aspect above.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0057] 1. Improve data security: By introducing the Galois field polynomial secret sharing mechanism, the present invention can effectively encrypt the DC coefficients and AC coefficients of JPEG images, thereby ensuring the data security of image thumbnails in the cloud storage environment and effectively preventing the malicious theft or abuse of image content.

[0058] 2. Retain browsability: The present invention makes full use of the JPEG compression characteristics. By selectively encrypting key coefficients, it realizes the generation of encrypted thumbnails with a certain degree of browsability while ensuring privacy protection, meeting the user's need for image preview. This balance not only improves the practicality of encryption but also broadens the application scenarios of the technology.

[0059] 3. High-efficiency compatibility: The method of the present invention directly acts on the JPEG encoding structure (such as DC coefficients and AC coefficients) without changing the existing JPEG storage and transmission formats, and has good compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a schematic diagram of the steps of the JPEG thumbnail protection method based on Galois field polynomial secret sharing;

[0061] Figure 2It is a module composition diagram of the JPEG thumbnail protection encryption and decryption system based on Galois field polynomial secret sharing;

[0062] Figure 3 It is a composition structure diagram of a computer device;

[0063] Figure 4 It is a schematic diagram of the JPEG compression method for images;

[0064] Figure 5 It is an example diagram for differential encoding and run-length encoding of the quantization coefficient matrix;

[0065] Figure 6 It is an example diagram of polynomial secret sharing encryption;

[0066] Figure 7 It is an example diagram of polynomial secret sharing decryption;

[0067] Figure 8 It is a display of the visual effects of encrypted images under different parameters. Specific implementation manners

[0068] To make the above objects, features, and advantages of the present invention more obvious and understandable, the specific implementation manners of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below. The technical features in various embodiments of the present invention can be combined correspondingly without conflict.

[0069] The present invention provides a method for protecting JPEG thumbnail based on Galois field polynomial secret sharing, aiming to achieve secure encryption and protection of JPEG image thumbnails stored in the cloud, while retaining a certain degree of browsability. The core idea of this method is Galois field polynomial secret sharing and JPEG compression characteristics. By selectively encrypting the direct current (DC) coefficients and alternating current (AC) coefficients of the image, it ensures data security while retaining the basic visual information of the image. In the Galois field, the polynomial secret sharing mechanism is used to disperse the key information into multiple shared values, achieving high-strength encryption and reliable storage of information. Experimental results show that the present invention has significant advantages in ensuring data security and browsability. Specifically, by performing Galois field encryption on the DC coefficients and AC coefficients of JPEG images, the generated encrypted images can effectively prevent content leakage or malicious exploitation, while retaining the general outline and basic visual information of the images, facilitating users to quickly identify. In a preferred embodiment of the present invention, a method for protecting JPEG thumbnail based on Galois field polynomial secret sharing is provided, which is used to encrypt JPEG images before they are transmitted to the cloud to ensure data privacy and security. The specific steps are as described in S1 to S8, as Figure 1 shown. The specific implementation methods of each step will be described in detail below.

[0070] S1. The image owner converts the color image to the YCbCr color space, and performs downsampling, pixel block division, discrete cosine transform, and quantization processing to obtain the quantization coefficient matrix of each pixel block.

[0071] In the embodiment of the present invention, the specific method of the above step S1 is as follows:

[0072] S11. The image owner converts the color image from the RGB color space to the YCbCr color space, where Y is the luminance component, and Cb and Cr are the chrominance components (grayscale images only have the luminance component and directly jump to step S13);

[0073] S12. Downsample the chrominance components Cb and Cr in the YCbCr color space to reduce their resolution (common sampling formats include 4:2:0 and 4:2:2);

[0074] S13. Divide the luminance component and the downsampled chrominance components into 8×8 pixel blocks, and each component is processed independently;

[0075] S14. Perform a discrete cosine transform (DCT) on each 8×8 pixel block to convert the spatial domain data into frequency domain data, generating a DCT coefficient matrix;

[0076] S15. Quantize each coefficient in the DCT coefficient matrix using a quantization table to obtain the quantization coefficient matrix.

[0077] S2. The image owner converts the quantization coefficient matrix of each pixel block into a one-dimensional sequence, with the first element of the sequence being the DC coefficient and the remaining elements being the AC coefficients. Then, differential coding is performed on the DC coefficients of all sequences to obtain the difference between each DC coefficient and the previous one, and run-length coding is performed on the AC coefficients of all sequences.

[0078] In an embodiment of the present invention, the specific method of the above step S2 is as follows:

[0079] S21. The image owner performs a zigzag scan on the quantization coefficient matrix of each pixel block to convert the two-dimensional matrix into a one-dimensional sequence. Among them, the first element of each sequence is the DC coefficient, and the remaining elements are the AC coefficients.

[0080] S22. Differential coding is performed on the DC coefficients of all sequences, and the difference between each DC coefficient and the previous one is calculated and represented by the binary tuple [ds p / dv p . Among them, ds p is the number of binary digits of the difference, dv p is the binary representation of the difference, and p is the index of the DC coefficient.

[0081] S23. Run-length coding is performed on the AC coefficients of all sequences, and each non-zero AC coefficient is recorded as a triple [(r q , s q ) / v q . Among them, r q represents the number of consecutive zero values before the non-zero coefficient, s q is the number of binary digits of the non-zero coefficient, v q is the binary representation of the non-zero coefficient, and q is the index of the non-zero AC coefficient.

[0082] S3. The image owner sets the modification amounts of the DC coefficients and the AC coefficients.

[0083] In an embodiment of the present invention, the specific method of the above step S3 is as follows:

[0084] S31. The image owner sets the modification amount of the DC coefficient to α (α≥0);

[0085] S32. The image owner sets the modification amount of the AC coefficient to β (β≥0).

[0086] S4. The image owner extracts the binary digits of the difference of each DC coefficient according to the modification amount of the DC coefficient and maps them to the corresponding Galois field numbers.

[0087] In an embodiment of the present invention, the specific method of the above step S4 is as follows:

[0088] S41. The image owner extracts the binary bits of the difference of each DC coefficient from the binary representation dv of the difference of each DC coefficient according to the smaller value between the modification amount α of the DC coefficient and the number of binary digits ds of its difference; specifically, when α ≤ ds p , the lowest α binary bits are extracted, and when α > ds p , the lowest ds p binary bits are extracted; p p ;

[0089] S42. Map the extracted binary bits to the corresponding Galois field numbers, denoted as the DC mapping number a 0 ; specifically, if α binary bits are extracted, they are mapped to the numbers on the Galois field GF(2 α ), and if ds p binary bits are extracted, they are mapped to the numbers on the Galois field .

[0090] S5. The image owner performs polynomial secret sharing on the mapping values of each DC coefficient on the corresponding Galois field, generates multiple encrypted DC mapping values, and converts them into multiple encrypted DC coefficient binary tuples.

[0091] In the embodiments of the present invention, the specific method of the above step S5 is as follows:

[0092] S51. The image owner constructs a (k - 1)-order polynomial 0 on the corresponding Galois field with the DC mapping number a of each DC coefficient as the basis, where a 1 , a 2 , …, a k-1 are randomly selected numbers in the Galois field, and p(x) is a fixed irreducible polynomial;

[0093] S52. Select n different identity numbers x 1 , x 2 , …, x n , and input them into the polynomial f(x) respectively, and calculate to obtain n encrypted DC mapping values f(x 1 ), f(x 2 ), …, f(x n );

[0094] S53. The n encrypted DC mapping values f(x 1 ), f(x 2 ), …, f(x n ​) Fill them into the binary bits of the difference values respectively to generate n encrypted binary pairs; specifically, if α binary bits are extracted in S41, then fill each DC mapping value into the lowest α bits, and if ds p binary bits are extracted in S41, then fill each DC mapping value into the lowest ds p bits;

[0095] S54. Verify whether all the differences corresponding to the n generated encrypted binary pairs satisfy that their DC coefficients are within the range where Q 00 is the quantization coefficient at the coordinate (0, 0) of the quantization table (which varies according to different quantization factors); if any binary pair does not meet the condition, randomly select a new set of coefficients a 1 , a 2 , …, a k-1 of the polynomial f(x), and repeat the above steps S52 and S53 until all the generated encrypted binary pairs meet the conditions.

[0096] S55. Repeat the steps of S51 and S54 for all DC coefficients until all DC coefficients are processed.

[0097] S6. The image owner extracts the binary bits of its non - zero values according to the modification amount of the AC coefficients and maps them to the corresponding Galois field numbers.

[0098] In the embodiment of the present invention, the specific method of the above step S6 is as follows:

[0099] S61. The image owner extracts the binary bits of the non - zero AC coefficients according to the modification amount β of the AC coefficients; specifically, when β ≤ s q , extract its lowest β binary bits, and when β > s q , extract its lowest s q binary bits;

[0100] S62. Map the binary bits extracted in S61 to the corresponding Galois field numbers, denoted as the AC mapping number b 0 ; specifically, if β binary bits are extracted, map them to the numbers on the Galois field GF(2 β ), and if s q binary bits are extracted, map them to the numbers on the Galois field .

[0101] S7. The image owner performs polynomial secret sharing on the mapping values of the AC coefficients on the corresponding Galois field to generate multiple encrypted AC mapping values and convert them into multiple encrypted AC coefficient triples.

[0102] In an embodiment of the present invention, the specific method of step S7 is as follows:

[0103] S71. The image owner constructs a polynomial of order (k - 1) on the corresponding Galois field with the number of AC mappings b of each non - zero AC coefficient as the base 0 where b , b 1 , b 2 , …, b k-1 are randomly selected numbers within the Galois field, and p(x) is a fixed irreducible polynomial;

[0104] S72. Select n different identity numbers x 1 , x 2 , …, x n , and input them into the polynomial g(x) to calculate n encrypted AC mapping values g(x 1 ), g(x 2 ), …, g(x n );

[0105] S73. Fill the n encrypted AC mapping values g(x 1 ), g(x 2 ), …, g(x n ) into the non - zero coefficient binary bits respectively to generate n encrypted triples; specifically, if β binary bits are extracted in S61, fill them into the lowest β bits, and if s q binary bits are extracted in S61, fill them into the lowest s q bits.

[0106] S74. Repeat steps S71 and S73 for each non - zero AC coefficient until all non - zero AC coefficients are processed.

[0107] S8. The image owner combines the generated multiple encrypted DC coefficient pairs and AC coefficient triples respectively to generate multiple encrypted JPEG images and uploads them to the cloud.

[0108] In an embodiment of the present invention, the specific method of step S8 is as follows:

[0109] S81. The image owner combines the encrypted pairs and encrypted triples corresponding to each identity number according to the n different identity numbers x 1 , x 2 , …, x n to generate n encrypted JPEG images;

[0110] S82. Distribute n encrypted JPEG images, n identity numbers, modification amounts α, β, and n and k to n receivers respectively, where each receiver obtains one encrypted JPEG image, one identity number, modification amounts α, β, and n and k.

[0111] Thus, based on the above S1 - S8 steps, the image owner can generate and encrypt a JPEG image. Meanwhile, through the selective encryption technology, while effectively protecting data privacy, the basic visual information of the image is retained, facilitating users to quickly identify the image content category. The JPEG images in the present invention can be JPEG images that need to be securely transmitted over the network in any scenario with sensitive information (such as medical images, financial files, and personal data).

[0112] It should be noted that the image owner and receivers in the present invention can both be clients with data - processing capabilities in the form of corresponding software or hardware, and the specific form is not limited.

[0113] In an embodiment of the present invention, there is also provided a decryption method for JPEG thumbnail protection based on Galois - field polynomial secret sharing corresponding to the above - mentioned S1 - S8 step encryption method. This decryption method is essentially the reverse process of the above - mentioned S1 - S8 step encryption method. Based on this decryption method, the method for any k receivers to decrypt the image by combining all their encrypted JPEG images and identity numbers is as follows:

[0114] S91. Any k participants pool all their k encrypted JPEG images to obtain k groups of DC coefficients and AC coefficients.

[0115] S92. Respectively convert the k groups of DC coefficients and AC coefficients into encrypted DC binary tuples and AC ternary tuples.

[0116] S93. Extract k encrypted difference binary bits at corresponding positions according to the DC modification amount α. Specifically, when α ≤ ds p , extract its lowest α binary bits; when α > ds p , extract its lowest ds p binary bits.

[0117] S94. Map the k extracted encrypted binary bits to corresponding Galois - field numbers f(x 1 ), f(x 2 ), …, f(x k ). Specifically, when α ≤ ds p , map it to a number in the Galois field GF(2 α ); when α > ds p , map it to the Galois field The numbers on;

[0118] S95. After obtaining k encrypted difference binary bits f(x 1 ), f(x 2 ), …, f(x k ), reconstruct the DC mapping number a 0 through the Lagrange interpolation polynomial and fill it into the binary tuple, where

[0119] S96. Repeat steps S93 - S95 until all encrypted DC coefficients at all positions are processed.

[0120] S97. Extract k encrypted non - zero coefficient binary bits at the corresponding positions according to the DC modification amount β; specifically, when β ≤ s q , extract its lowest β binary bits, and when β > s q , extract its lowest s q binary bits;

[0121] S98. Map the extracted k encrypted non - zero coefficient binary bits to the corresponding Galois field numbers g(x 1 ), g(x 2 ), …, g(x k ); specifically, when β ≤ s q , map it to the number on the Galois field GF(2 β ), and when β > s q , map it to the number on the Galois field ;

[0122] S99. After obtaining k encrypted non - zero coefficient binary bits g(x 1 ), g(x 2 ), …, g(x k ), reconstruct the DC mapping number b 0 through the Lagrange interpolation polynomial and fill it into the triple, where

[0123] S910. Repeat steps S97 - S99 until all encrypted AC coefficients at all positions are processed.

[0124] S911. Combine the obtained DC coefficients and AC coefficients to obtain the original JPEG image.

[0125] Similarly, based on the same inventive concept, as Figure 2 shown, the present invention also provides a JPEG thumbnail protection encryption and decryption system based on Galois field polynomial secret sharing, which includes:

[0126] An encryption system, which is used to generate an encrypted JPEG image according to the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing described in S1 - S8 above and store it in the cloud;

[0127] A decryption system, which is used to decrypt the encrypted JPEG image jointly by multiple recipients according to the JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing described in S91 - S911 above.

[0128] It should be noted that the above encryption system and decryption system can be set on different computer devices respectively.

[0129] Similarly, based on the same inventive concept, as Figure 3 shown, the present invention also provides a computer electronic device corresponding to a JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing or a JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing provided in the above embodiments. It includes a memory and a processor;

[0130] The memory is used to store computer programs;

[0131] The processor is used to implement the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing as described above when executing the computer program, or execute the JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing as described above.

[0132] In addition, when the logical instructions in the above memory are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention.

[0133] Therefore, based on the same inventive concept, the present invention provides a computer-readable storage medium corresponding to a JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing or a JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing. A computer program is stored on the storage medium. When the computer program is executed by a processor, it can implement the encrypted domain three-dimensional mesh model steganography method based on ripple prediction as described above.

[0134] Accordingly, based on the same inventive concept, the present invention provides a computer program product including computer programs / instructions, which, when executed by a processor, can implement the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing as described above, or execute the JPEG thumbnail protection decryption method based on Galois field polynomial secret sharing as described above.

[0135] It can be understood that the above storage medium may include a random access memory (RAM), and may also include a non-volatile memory (NVM), such as at least one disk memory. Meanwhile, the storage medium may also be various media that can store program codes, such as a USB flash drive, a mobile hard disk, a magnetic disk, or an optical disc.

[0136] It can be understood that the above processor may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0137] In addition, it should be noted that those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working process of the above-described system can refer to the corresponding process in the foregoing method embodiments, and will not be elaborated herein. In the embodiments provided in the present application, the division of steps or modules in the system and method is only a logical function division, and there may be other division methods in actual implementation. For example, multiple modules or steps may be combined or integrated together, and one module or step may also be split.

[0138] To better understand the specific implementation process of encryption and decryption of the above steps S1 to S8 and S91 to S911 of the present invention, the following uses an example to detail the specific steps and technical effects of the present invention.

[0139] Embodiment

[0140] In this embodiment, a JPEG thumbnail protection encryption and decryption method based on Galois field polynomial secret sharing is as specifically shown in steps 1 to 9, where steps 1 to 8 show the encryption process and step 9 shows the decryption process. The following describes the specific implementation manners of steps 1 to 9 in detail.

[0141] Step 1: The method for the image owner to perform color space conversion, sampling, blocking, discrete cosine transform, and quantization processing on the image to obtain a quantized coefficient matrix is as follows:

[0142] Step 11: The image owner converts the color image from the RGB color space to the YCbCr color space, where Y is the luminance component, and Cb and Cr are the chrominance components (a grayscale image only has a luminance component and directly jumps to step S13);

[0143] Step 12: Downsample the chrominance components Cb and Cr in the YCbCr color space to reduce their resolution (common sampling formats include 4:2:0 and 4:2:2);

[0144] Step 13: Divide the luminance component and the downsampled chrominance components into 8×8 pixel blocks, and each component is processed independently;

[0145] Step 14: Perform a discrete cosine transform (DCT) on each 8×8 pixel block to convert the spatial domain data into frequency domain data, generating a DCT coefficient matrix;

[0146] Step 15: Quantize each coefficient in the DCT coefficient matrix using a quantization table to obtain a quantized coefficient matrix.

[0147] In this embodiment, for the convenience of understanding, an example diagram of a JPEG compression of an image is provided, as Figure 4 shown.

[0148] Step 2: The method for the image owner to perform differential coding and run-length coding on the quantized coefficient matrix of each pixel block is as follows:

[0149] Step 21: The image owner performs a zigzag scan on the quantized coefficient matrix of each pixel block to convert the two-dimensional matrix into a one-dimensional sequence. Among them, the first element of each sequence is the DC coefficient, and the remaining elements are the AC coefficients.

[0150] Step 22: Perform differential coding on the DC coefficients of all sequences, calculate the difference between each DC coefficient and the previous DC coefficient, and represent it using the binary tuple [ds p / dv p . Among them, ds p is the number of bits of the binary representation of the difference, dv p is the binary representation of the difference, and p is the index of the DC coefficient.

[0151] Step 23: Perform run - length encoding on the AC coefficients of all sequences, and record each non - zero AC coefficient as a triple [(r q , s q ) / v q . Where r q represents the number of consecutive zero values before the non - zero coefficient, s q is the number of binary digits of the non - zero coefficient, v q is the binary representation of the non - zero coefficient, and q is the index of the non - zero AC coefficient.

[0152] In this embodiment, for the sake of easy understanding, a digitization example is provided, as shown in Figure 5 . In this example, we assume it is the first DCT coefficient matrix. Since it is the first DCT coefficient matrix, there are no other DC coefficients in front of its DC coefficient 20, so the calculated difference is 20; this difference is represented as a binary pair [ds 1 / dv 1 = [5 / 10110], where 5 is the number of binary digits of the difference, and 10110 is the binary representation of the difference. The first non - zero AC coefficient 1 is represented as [(r 1 , s 1 ) / v 1 = [(0, 1) / 1], where the first term 0 represents the number of consecutive zeros before the non - zero coefficient, the middle term 1 represents the number of binary digits of the coefficient, and the last term 1 is the binary representation of the coefficient. All subsequent AC coefficients adopt the same triple - encoding method.

[0153] Step 3: The method for the image owner to set the modification amounts of the DC coefficient and the AC coefficient is as follows:

[0154] Step 31: The image owner sets the modification amount of the DC coefficient to α (α ≥ 0);

[0155] Step 32: The image owner sets the modification amount of the AC coefficient to β (β ≥ 0).

[0156] Step 4, the method for the image owner to extract the binary digits of the difference of each DC coefficient according to the DC - coefficient modification amount and map them to the corresponding Galois - field numbers is as follows:

[0157] Step 41: The image owner extracts the binary digits of the difference of the DC coefficient from the binary representation dv p of the difference of each DC coefficient according to the smaller value between the modification amount α of the DC coefficient and the number of binary digits ds p ; specifically, when α ≤ ds p , extract the lowest α binary digits, and when α > ds pWhen, extract its lowest ds p binary digits;

[0158] Step 42: Map the binary digits extracted in Step 41 to the corresponding Galois field numbers, denoted as the DC mapping number a 0 ; Specifically, if α binary digits are extracted, map them to the numbers on the Galois field GF(2 α ), if ds p binary digits are extracted, map them to the numbers on the Galois field .

[0159] In this embodiment, for the sake of easy understanding, we take the example in Figure 5 to illustrate. We assume that the modification amount α of the DC coefficient is 3, and the binary tuple of the DC coefficient is [ds 1 / dv 1 = [5 / 10110]. Since 3 < 5, we extract the lowest 3 difference binary digits, that is, 110. Correspondingly, we will map it to the number on the Galois field GF(2 3 ), denoted as the DC mapping number a 0 = 110.

[0160] Step 5: The method for the image owner to perform polynomial secret sharing on the mapping values of each DC coefficient on the corresponding Galois field, generate multiple encrypted DC mapping values, and convert them into multiple encrypted DC coefficient binary tuples is as follows:

[0161] Step 51: The image owner constructs a (k - 1)-order polynomial 0 on the corresponding Galois field with the DC mapping number a of each DC coefficient as the basis 1 ,a 2 ,…,a k-1 are randomly selected numbers in the Galois field, and p(x) is a fixed irreducible polynomial;

[0162] Step 52: Select n different identity numbers x 1 ,x 2 ,…,x n , and input them into the polynomial f(x) respectively to obtain n encrypted DC mapping values f(x 1 ),f(x 2 ),…,f(x n );

[0163] In this embodiment, for the sake of easy understanding, a digital example of polynomial secret sharing on the Galois field is provided, as shown in Figure 6 . Here, we assume k = 3, n = 4, and the Galois field is GF(2 8), the DC mapping number a 0 = 10110011, and the four identity numbers are x 1 = 00000001, x 2 = 00000010, x 3 = 00000011, x 4 = 00000100, p(x) = x 8 + x 4 + x 3 + x + 1. Through polynomial secret sharing, we transform the DC mapping number a 0 = 10110011 into four encrypted DC mapping values, which are f(x 1 ) = 11100101, f(x 2 ) = 01011110, f(x 3 ) = 10010011, f(x 4 ) = 00101101.

[0164] Step 53: Fill the n encrypted DC mapping values f(x 1 ), f(x 2 ), …, f(x n ) into the binary bits of the difference respectively to generate n encrypted binary pairs; specifically, if α binary bits are extracted in S41, then each DC mapping value is filled into the lowest α bits, if ds p binary bits are extracted in S41, then each DC mapping value is filled into the lowest ds p bits;

[0165] Step 54: Verify whether the differences corresponding to the n generated encrypted binary pairs all satisfy that their DC coefficients are within the range , where Q 00 is the quantization coefficient at the coordinate (0, 0) of the quantization table (varying according to different quantization factors); if any binary pair does not meet the condition, then randomly select a new set of coefficients a 1 , a 2 , …, a k-1 of the polynomial f(x) and repeat the above steps 52 - step 53 until all the n generated encrypted binary pairs meet the conditions.

[0166] Step 55: Repeat steps 514 and 54 for each DC coefficient until all DC coefficients are processed.

[0167] Step 6: The method for the image owner to extract the binary bits of the non - zero values according to the AC coefficient modification amount and map them to the corresponding Galois field numbers is as follows:

[0168] Step 61: The image owner extracts the binary bits of the non-zero AC coefficients according to the modification amount β of the AC coefficients. Specifically, when β ≤ s q , the lowest β binary bits are extracted. When β > s q , the lowest s q binary bits are extracted;

[0169] Step 62: Map the binary bits extracted in Step 61 to the corresponding Galois field numbers, denoted as the AC mapping number b 0 ; specifically, if β binary bits are extracted, they are mapped to the numbers in the Galois field GF(2 β ). If s q binary bits are extracted, they are mapped to the numbers in the Galois field .

[0170] In this embodiment, for the sake of understanding, we take the example in Figure 5 for illustration. We assume that the modification amount β of the first AC coefficient is 3, and the triple of the first AC coefficient is [(r 1 , s 1 ) / v 1 = [(0, 1) / 1]. Since 3 > 1, we extract the lowest 1 difference binary bit, which is 1. Correspondingly, we map it to the number in the Galois field GF(2 1 ), denoted as the DC mapping number b 0 = 1.

[0171] Step 7: The image owner performs polynomial secret sharing on the mapping values of the AC coefficients in the corresponding Galois field to generate multiple encrypted AC mapping values, and the method of converting them into multiple encrypted AC coefficient triples is as follows:

[0172] Step 71: The image owner constructs a (k - 1)-order polynomial 0 on the corresponding Galois field with the AC mapping number b of each non-zero AC coefficient as the basis, where b 1 , b 2 , …, b k-1 are randomly selected numbers in the Galois field, and p(x) is a fixed irreducible polynomial;

[0173] Step 72: Select n different identity numbers x 1 , x 2 , …, x n , and input them into the polynomial g(x) to obtain n encrypted AC mapping values g(x 1 ), g(x 2 ), …, g(x n );

[0174] In this embodiment, the mapping value b of the AC coefficient 0 is subjected to polynomial secret sharing to generate multiple encrypted AC mapping values g(x 1 ), g(x 2 ), …, g(x n ) in the same manner as in Steps 51 and 52.

[0175] Step 73: Fill the n encrypted AC mapping values g(x 1 ), g(x 2 ), …, g(x n ) into the non-zero coefficient binary bits respectively to generate n encrypted triples; specifically, if β binary bits are extracted in S61, then fill them into the lowest β bits, and if s q binary bits are extracted in S61, then fill them into the lowest s q bits.

[0176] Step 74: Repeat Steps 71 - 73 for each non-zero AC coefficient until all non-zero AC coefficients are processed.

[0177] Step 8: The method for the image owner to combine the generated multiple encrypted DC coefficient pairs and AC coefficient triples respectively to generate multiple encrypted JPEG images and upload them to the cloud is as follows:

[0178] Step 81: The image owner combines the encrypted pair and the encrypted triple corresponding to each identity number according to n different identity numbers x 1 , x 2 , …, x n to generate n encrypted JPEG images;

[0179] Step 82: Distribute the n encrypted JPEG images, the n identity numbers, the modification amounts α, β, and n and k to n receivers respectively, where each receiver obtains one encrypted JPEG image, one identity number, the modification amounts α, β, and n and k.

[0180] Step 9: After n receivers respectively receive one encrypted JPEG image, one identity number, the modification amounts α, β, and n and k generated by the encryption method according to any one of Claims 1 to 8, the method for any k receivers to perform image decryption by combining all their encrypted JPEG images and identity numbers.

[0181] Step 91: Any k participants gather all their k encrypted JPEG images to obtain k groups of DC coefficients and AC coefficients;

[0182] Step 92: Convert k groups of DC coefficients and AC coefficients into encrypted DC binary tuples and AC ternary tuples respectively;

[0183] Step 93: Extract k encrypted difference binary bits at corresponding positions according to the DC modification amount α; specifically, when α ≤ ds p , extract its lowest α binary bits, and when α > ds p , extract its lowest ds p binary bits;

[0184] Step 94: Map the k extracted encrypted binary bits to the corresponding Galois field numbers f(x 1 ), f(x 2 ), …, f(x k ); specifically, when α ≤ ds p , map it to a number in the Galois field GF(2 α ), and when α > ds p , map it to a number in the Galois field ;

[0185] Step 95: After obtaining k encrypted difference binary bits f(x 1 ), f(x 2 ), …, f(x k ), reconstruct the DC mapping number a 0 through the Lagrange interpolation polynomial and fill it into the binary tuple, where

[0186]

[0187] In this embodiment, for the convenience of understanding, a numerical example of the Lagrange interpolation polynomial reconstruction is provided, as shown in Figure 7 . Here, we assume that k = 3, n = 4, the Galois field is GF(2 8 ), p(x) = x 8 + x 4 + x 3 + x + 1, and there are 3 receivers pooling their identity numbers, which are x 1 = 00000001, x 2 = 00000010, x 3 = 00000011 and 3 encrypted DC mapping values, which are f(x 1 ) = 11100101, f(x 2 ) = 01011110, f(x 3 ) = 10010011. By substituting into the Lagrange interpolation polynomial, the DC mapping value a 0 = 10110011 can be reconstructed.

[0188] Step 96. Repeat steps 93 to 95 until all encrypted DC coefficients at all positions are processed.

[0189] Step 97. Extract k encrypted non-zero coefficient binary bits at the corresponding positions according to the DC modification amount β; specifically, when β ≤ s q , extract its lowest β binary bits, and when β > s q , extract its lowest s q binary bits;

[0190] Step 98. Map the extracted k encrypted non-zero coefficient binary bits to the corresponding Galois field numbers g(x 1 ), g(x 2 ), …, g(x k ); specifically, when β ≤ s q , map it to a number in the Galois field GF(2 β ), and when β > s q , map it to a number in the Galois field ;

[0191] Step 99. After obtaining the k encrypted non-zero coefficient binary bits g(x 1 ), g(x 2 ), …, g(x k ), reconstruct the DC mapping number b 0 through the Lagrange interpolation polynomial and fill it into the triple, where

[0192] In this embodiment, the method of reconstructing the mapping value b 0 of the AC coefficient through the Lagrange interpolation polynomial is the same as step 95.

[0193] Step 910. Repeat steps 97 to 99 until all encrypted AC coefficients at all positions are processed.

[0194] Step 911. Combine the obtained DC coefficients and AC coefficients to obtain the original JPEG image.

[0195] In this embodiment, the privacy protection of the encrypted domain three-dimensional grid model is performed according to the aforementioned steps 1 to 8, and its specific visual effect display is as Figure 8 shown. In Figure 8 , (a) is the original image, and (b)-(f) are the results of α = β = 1, α = β = 2, α = β = 3, α = β = 4, α = β = 5 respectively.

[0196] In summary, the present invention adopts a selective encryption method, which can not only protect data privacy but also retain the basic visual features of the image. This solution not only effectively prevents the thumbnails uploaded to cloud storage from being maliciously stolen or misused, but also facilitates users to quickly identify the image content, achieving a good balance between data security and usability.

[0197] The above-described embodiments are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by adopting the means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A JPEG thumbnail protection method based on Galois field polynomial secret sharing, characterized in that: include: S1. The image owner converts the color image into the YCbCr color space, and performs downsampling, pixel blocking, discrete cosine transform and quantization processing to obtain a quantization coefficient matrix for each pixel block; S2, the image owner converts the quantization coefficient matrix of each pixel block into a one-dimensional sequence, with the first element of the sequence as the DC coefficient and the remaining elements as the AC coefficients, and then performs differential encoding on the DC coefficients of all sequences, and obtains the difference of each DC coefficient relative to the previous DC coefficient, and performs run-length encoding on the AC coefficients of all sequences; S3, the image owner sets the DC coefficient and AC coefficient modification amount; S4, the image owner extracts the binary bits of the difference of each DC coefficient according to the DC coefficient modification amount, and maps it to the corresponding Galois field number; S5, the image owner performs polynomial secret sharing on the mapping value of each DC coefficient on the corresponding Galois field, generates multiple encrypted DC mapping values, and converts them into multiple encrypted DC coefficient tuples; S6, the image owner extracts the binary bits of the non-zero value according to the AC coefficient modification amount, and maps them to the corresponding Galois field number; S7, the image owner performs polynomial secret sharing on the mapping value of the AC coefficient on the corresponding Galois field, generates multiple encrypted AC mapping values, and converts them into multiple encrypted AC coefficient triplets; S8. The image owner combines the generated multiple encrypted DC coefficient binary tuples with the AC coefficient triples to generate multiple encrypted JPEG images and upload them to the cloud.

2. The JPEG thumbnail protection method based on Galois field polynomial secret sharing according to claim 1, characterized in that: The specific method of S2 is as follows: S21, the image owner performs a zigzag scan on the quantization coefficient matrix of each pixel block, and converts the two-dimensional matrix into a one-dimensional sequence, wherein the first element of each sequence is a DC coefficient, and the remaining elements are AC coefficients; S22, perform differential encoding on the DC coefficients of all sequences, calculate the difference between each DC coefficient and the previous DC coefficient, and use the binary number ds of the difference p , binary representation of the difference dv p The composed two-tuple representation; S23, perform run-length coding on the AC coefficients of all sequences, and record each non-zero AC coefficient as the number of consecutive zero values ​​before the non-zero AC coefficient r q , the number of binary digits of the non-zero AC coefficient is s q , the binary representation of the non-zero AC coefficient v q The composed triplet.

3. According to the JPEG thumbnail protection method based on Galois field polynomial secret sharing according to claim 2, the specific method of S4 is as follows: S41, the image owner calculates the amount of modification α of the DC coefficient and the binary number ds of the difference p The smaller of the two, from the binary representation of the difference of each DC coefficient dv p Extract the difference binary bits of the DC coefficient; when α≤ds p When α>ds p When the lowest ds is extracted p binary bits; S42, mapping the binary bits extracted in S41 to corresponding Galois field numbers, recorded as DC mapping number a0.

4. The JPEG thumbnail protection method based on Galois field polynomial secret sharing according to claim 3, characterized in that: The specific method of S5 is as follows: S51, the image owner constructs a (k-1)-order polynomial f(x) on the corresponding Galois field using the DC mapping number a0 of each DC coefficient as a basis and k-1 numbers randomly selected in the Galois field as coefficients; S52, selecting n different identity numbers and inputting them into the polynomial f(x) respectively, to obtain n encrypted DC mapping values; S53, respectively fill the n encrypted DC mapping values ​​into the binary bits of the difference to generate n encrypted binary tuples; if the binary bits extracted in S41 are α, then fill each DC mapping value into the lowest α bits; if the binary bits extracted in S41 are ds p binary bits, each DC-mapped value is filled into the lowest ds p Bit; S54, verify whether the differences corresponding to the generated n encrypted binary groups all satisfy that their DC coefficients are within the range In which Q 00 is the quantization coefficient of the quantization table at the coordinate (0,0); if any two-tuple does not meet the conditions, a set of coefficients of the polynomial f(x) is randomly selected again, and the above steps S52 and S53 are repeated until all the generated n encrypted two-tuples meet the conditions.

5. The JPEG thumbnail protection method based on Galois field polynomial secret sharing according to claim 4, characterized in that: The specific method of S6 is as follows: S61, the image owner extracts the binary bits of the non-zero AC coefficients according to the modification amount β of the AC coefficients; when β≤s q When β>s q When the lowest s is extracted q binary bits; S62, mapping the binary bits extracted in S61 to corresponding Galois field numbers, recorded as AC mapping number b0;.

6. The JPEG thumbnail protection method based on Galois field polynomial secret sharing according to claim 5, characterized in that: The specific method of S7 is as follows: S71. The image owner constructs a (k-1)-order polynomial g(x) on the corresponding Galois field using the AC mapping number b0 of each non-zero AC coefficient as a basis and k-1 numbers randomly selected in the Galois field as coefficients; S72, selecting n different identity numbers and inputting them into the polynomial g(x) to obtain n encrypted communication mapping values; S73, respectively fill the n encrypted AC mapping values ​​into the non-zero coefficient binary bits to generate n encrypted triples; if the β binary bits extracted in S61 are filled in, fill in the lowest β bits; if the s binary bits extracted in S61 are filled in, q binary digits, fill in the lowest s q Bit.

7. The JPEG thumbnail protection method based on Galois field polynomial secret sharing according to claim 6, characterized in that: The specific method of S8 is as follows: S81, the image owner generates n encrypted JPEG images based on n different identity numbers and combining the encryption binary and encryption triplet corresponding to each identity number; S82. Distribute n encrypted JPEG images, n identity numbers, modification amounts α, β, and n and k to n receivers respectively, wherein each receiver obtains an encrypted JPEG image, an identity number, modification amounts α, β, and n and k.

8. A JPEG thumbnail protection encryption and decryption system based on Galois field polynomial secret sharing, characterized in that: include: An encryption system for generating an encrypted JPEG image and storing it in the cloud according to the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing as described in claim 1; The decryption system is used to decrypt the encrypted JPEG image according to the inverse process of the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing.

9. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by the processor, the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing as claimed in claim 1 can be implemented.

10. A computer electronic device, characterized in that: including memory and processor; The memory is used to store computer programs; The processor is used to implement the JPEG thumbnail protection encryption method based on Galois field polynomial secret sharing as claimed in claim 1 when executing the computer program.

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