A 3D model encryption method based on coordinate regularization

Abstract

The application discloses a 3D model encryption method based on coordinate regularization, and relates to the technical field of 3D model encryption; the method comprises the following steps: acquiring vertex coordinate data of a 3D model, and constructing a vertex coordinate matrix; converting the vertex coordinate data into integers in the range of 0-255 through a regularization method, and constructing a two-dimensional numerical matrix; encrypting the two-dimensional numerical matrix by using an encryption method in a permutation-diffusion model and variants thereof; converting the encrypted two-dimensional numerical matrix into vertex coordinate data conforming to the format of the 3D model, and forming a format-compatible encrypted 3D model. In the application, the 3D model encryption method realizes data structure simplification by using coordinate regularization, designs multiple encryption prototypes (such as row-column permutation, XOR diffusion, modulo addition diffusion and AES encryption) to enhance security, realizes a more generalized encryption method, and is suitable for 3D data privacy protection in multimedia fields such as industrial manufacturing, medical treatment and 3D modeling.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of 3D model encryption, and particularly relates to a 3D model encryption method based on coordinate regularization. BACKGROUND

[0002] With the development of three-dimensional scanning technology and computer vision, 3D models have been widely used in many fields, such as industrial design, medical treatment, education and entertainment, etc. 3D modeling and 3D printing technology are also increasingly applied to life, and by using these technologies, lifelike objects in real life can be created, and the development of virtual reality is greatly promoted. Compared with 2D images, three-dimensional models contain more abundant and detailed object information; three-dimensional information is more comprehensive, and the projection between views is more accurate; the object can be observed from various angles; the interaction is strong, and the user experience is more abundant. However, the data used to describe the geometry, texture and other attributes of the 3D model has a high commercial value in the military, finance, cultural relic protection and highly confidential industries, and the leakage of the 3D model may cause incalculable losses. Therefore, the protection of 3D files is crucial to prevent illegal copying, tampering or unauthorized access.

[0003] Traditional 3D model encryption uses algorithms such as three-dimensional coordinates, mesh surfaces and textures to encrypt, so that the encrypted model only retains spatial and dimensional characteristics and cannot identify its visual features after encryption. A cascading chaotic system is constructed to encrypt the 3D model and select the encryption method. Some researchers use coordinate regularization to convert the coordinates into binary bytes, and through a sliding window, the tail of the binary bytes is encrypted to achieve format-compatible encryption of the 3D model. However, in the above encryption process, the vertex coordinate discrete value data is mainly encrypted, and compared with integer encryption, a more generalized encryption method cannot be achieved.

[0004] To overcome the above shortcomings, the application designs a more generalized encryption method, converts the coordinates into 0-255 integers through coordinate regularization, constructs a two-dimensional coordinate matrix, designs six encryption protocols, and encrypts the two-dimensional coordinate matrix to achieve 3D model encryption. SUMMARY

[0005] The purpose of the application is to provide a 3D model encryption method based on coordinate regularization to solve the problems of the prior art in the background art, such as mainly encrypting vertex coordinate discrete value data and being unable to achieve a more generalized encryption method.

[0006] To achieve the above purpose, the application adopts the following technical solutions:

[0007] The application provides a 3D model encryption method based on coordinate regularization, comprising the following steps:

[0008] S1, acquiring vertex coordinate data of a 3D model and constructing a vertex coordinate matrix;

[0009] S2, converting the vertex coordinate data into integers in the range of 0-255 through a regularization method and constructing a two-dimensional numerical matrix;

[0010] S3, encrypting the two-dimensional numerical matrix by using a substitution-diffusion model and encryption methods in variants thereof;

[0011] S4, converting the encrypted two-dimensional numerical matrix into vertex coordinate data conforming to the format of the 3D model and forming a format-compatible encrypted 3D model.

[0012] Preferably, the S1 specifically comprises the following steps:

[0013] The vertex coordinates of the 3D model are extracted from the storage data of various formats of the 3D model, and the vertex format is as follows:

[0014]

[0015]

[0016] The vertex coordinate matrix is constructed and represented as follows:

[0017]

[0018] wherein, P represents a vertex of the 3D model, represents the number of elements in the data set, contains three elements, i.e., the Cartesian coordinates of each vertex .

[0019] Preferably, the S2 specifically comprises the following steps:

[0020] S201, converting the vertex coordinate floating point number into a 32-bit binary number according to the IEEE754 standard;

[0021] S202, converting the coordinate data of each vertex into a 32-bit binary form, so that each vertex obtains a 96-bit bit stream;

[0022] S203, converting each vertex coordinate bit stream into a decimal number every 8-bit binary bit, forming 12 integers in the range of 0-255 through conversion;

[0023] S204, taking the converted vertex coordinates as columns and the number of vertices as rows to form a final two-dimensional matrix Q;

[0024] The two-dimensional matrix Q is expressed as:

[0025]

[0026] in, For the i Vertex j integers.

[0027] Preferably, the S3 specifically includes the following steps:

[0028] S301, designing a secret key generation method to generate a random sequence;

[0029] S302, the encryption method in the substitution-diffusion model and its variants uses a random sequence to encrypt a two-dimensional numerical matrix.

[0030] Furthermore, the S301 is specifically as follows:

[0031] Generate a secret key using the SHA-256 function , the secret key Divided into 5 parts:

[0032]

[0033] in, is a 32-bit binary number, The first 4 bits are converted into 4 values ​​as the 4 parameters of the pseudo-random function in the next step. , Control the number of iterations of the pseudo-random function;

[0034] The pseudo-random function is as follows:

[0035]

[0036] The iteration of the pseudo-random function ends and two random sequences are generated.

[0037] Furthermore, the substitution-diffusion model in S302 and its variants include 6 encryption methods, which are row-column substitution encryption, block substitution encryption, XOR diffusion encryption, modular diffusion encryption, XOR and row-column substitution encryption, and AES encryption. Any one of the 6 encryption methods is used to encrypt a two-dimensional numerical matrix.

[0038] Specifically, there are 6 encryption methods, as follows:

[0039] S3021, row-column permutation encryption: For two random sequences, sort the random sequences by numerical value, obtain the sorted sequence numbers, and use them as row and column indices; re-sort the sequences according to the row and column indices, and the re-sorted two-dimensional matrix is ​​the encrypted two-dimensional matrix;

[0040] S3022. Block permutation encryption: For two random sequences, select one of them, remap the subscripts of the random sequence to form a regularized vector, and organize the vector into a matrix T in a row-first manner;

[0041] The matrix T is:

[0042]

[0043] Set the block size to , the two-dimensional matrix Q is Rows are grouped into blocks ; The matrix T is also divided into the same blocks ; By Sort the values ​​in ;according to chaos The data in is obtained to obtain the encrypted two-dimensional matrix;

[0044] S3023, XOR Diffusion Encryption: Matrix constructed by S3022 , obtained by removing the identifier ,Will Multiply , obtained by rounding down , its formula is expressed as:

[0045]

[0046] in, An integer in the range ;

[0047] right Modulo 256 operation to obtain an integer in the range 0-255 , its formula is expressed as:

[0048]

[0049] Similarly, Converted into 8-bit binary bytes; finally the two-dimensional matrix Q and Perform bitwise XOR operation to obtain the encrypted two-dimensional matrix;

[0050] S3024, Modular Diffusion Encryption: Matrix constructed by S3022 T ,WillT multiplied by , and rounded down to get , the formula is:

[0051]

[0052] two-dimensional matrix Q and sum operation and then modulo 256, get encrypted two-dimensional matrix; formula for modulo addition operation:

[0053]

[0054] S3025, XOR and row-column permutation encryption: first according to S3023 on two-dimensional matrix XOR diffusion encryption, and then according to S3021 row-column permutation encryption, get encrypted two-dimensional matrix;

[0055] S3026, AES encryption: using CFB mode; the initialization vector 128-bit vector and 256-bit key input to the AES function, generate 128-bit output; every 16 8-byte integers into a block , AES encryption output and data block XOR operation, get encrypted results C ; as the new initialization vector, continue to encrypt the next block of data, in turn, until all blocks are encrypted, get encrypted two-dimensional matrix; C

[0056] wherein block method as shown in the following formula:

[0057]

[0058]

[0059] wherein, each block has 16 integers that is 128 bytes.

[0060] Preferably, the S4 specifically includes the following steps:

[0061] S401, encrypted two-dimensional matrix each value into 8-bit binary number, and then combined into a binary 96-bit form of matrix;

[0062] S402, according to IEEE 754 standard, every 32-bit into real number N, conversion formula as follows:

[0063]

[0064] wherein, m binary mantissa part, e binary exponent part,​s is a binary identifier, usually 0, 1;

[0065] S403, forming the encrypted vertex coordinate matrix , the format is:

[0066]

[0067] S404, obtain the encrypted 3D model by aggregating the encrypted points and surfaces.

[0068] Compared with the prior art, the beneficial effects of the present application are:

[0069] (1) The present application proposes a coordinate regularization 3D model encryption method, which solves the challenge of complex data structure of 3D objects to encryption. The present application realizes data structure simplification by using coordinate regularization, converts the data structure of a three-dimensional model into a two-dimensional numerical matrix, simplifies the complexity of the traditional three-dimensional object encryption method, enables existing two-dimensional image encryption technology to be directly applied to three-dimensional objects, realizes a more generalized encryption method, and significantly reduces the design and implementation difficulty of the encryption algorithm.

[0070] (2) The 3D model encryption method in the present application designs multiple encryption prototypes (such as row-column permutation, XOR diffusion, modulo addition diffusion, and AES encryption) to enhance security, and the encrypted three-dimensional object has good anti-statistical properties, such as high randomness and strong uniformity, which is difficult to infer the characteristics of the original object through statistical analysis.

[0071] (3) The encryption mechanism proposed by the 3D model encryption method in the present application can maintain the format compatibility of the three-dimensional model, without changing the format of the original data, so that the encrypted three-dimensional model can seamlessly adapt to existing three-dimensional model processing systems and application scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0072] Figure 1 is a flowchart of the 3D model encryption method based on coordinate regularization in the present application;

[0073] Figure 2 is a flowchart of generating a random sequence in the present application;

[0074] Figure 3 is a schematic diagram of the change of the two-dimensional numerical matrix in the present application. DETAILED DESCRIPTION

[0075] With reference to the drawings and embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0076] Embodiment 1

[0077] As shown in the following, the 3D model encryption method based on coordinate regularization includes the following steps: Figure 1

[0078] In the first step, the vertex coordinate data of the 3D model is obtained, and a coordinate matrix is constructed.

[0079] In the vertex coordinate data of the 3D model, the 3D model is stored in a format that can be understood by a computer, which includes but is not limited to obj, stl, stp and max, etc. The 3D file format can store four key features: the geometric shape of the model, the surface texture of the model, the scene details and any animation of the model.

[0080] In this embodiment, the geometric shape of the 3D model is mainly used to obtain the vertex coordinate data of the 3D model, wherein the vertex format is:

[0081]

[0082]

[0083] wherein, P is the vertex of the 3D model, represents the number of elements in the data set, contains three elements, i.e. the Cartesian coordinates of each vertex .

[0084] The vertex coordinate matrix is constructed, and the format is:

[0085]

[0086] In the second step, the vertex coordinate data is regularized to an integer in the range of 0-255, and a two-dimensional numerical matrix is constructed.

[0087] According to the IEEE754 standard, the vertex coordinate floating point number is converted into a 32-bit binary number.

[0088] The coordinate data of each vertex ​All are converted into 32-bit binary form, that is, each vertex can be represented as a 96-bit bit stream. For each vertex coordinate bit stream, every 8-bit binary is converted to decimal to form an integer of 0~255, and 12 integers are formed by conversion. The converted vertex coordinates are used as columns, and the number of vertices is used as rows to form the final two-dimensional matrix Q.

[0089] where the two-dimensional matrix Q is:

[0090]

[0091] where, is the i th integer of the j th vertex.

[0092] Third, the permutation-diffusion model and its variants are used to encrypt the two-dimensional numerical matrix.

[0093] First, generate a random sequence; Figure 2 The generation process of the random sequence is described, and further detailed as follows:

[0094] Generate a secret key by SHA-256 function Further divide the secret key into 5 parts:

[0095]

[0096] where, is a 32-bit binary number, is 128 bits. The first 4 bits are converted into 4 values as the 4 parameters of the next pseudo-random function controls the number of iterations of the pseudo-random function.

[0097] The further pseudo-random function is as follows:

[0098]

[0099] Two random number sequences are generated by the above method.

[0100] Second, design 6 encryption methods using permutation and diffusion model and its variants; Figure 3 The generation process of the encrypted two-dimensional numerical matrix is described, and the encryption protocol is as follows:

[0101] 1) Row and column permutation protocol: Sort the generated random sequences by value, get the sorted sequence number as row index and column index; reorder according to the row and column indexes, and the reordered two-dimensional matrix is the encrypted two-dimensional matrix.

[0102] 2) Block permutation protocol: through the two random sequences generated above, one of the sequences is selected, the subscripts of the random sequence are remapped to form a normalized vector, and the vector is organized into a matrix T in row priority;

[0103] The matrix T is:

[0104]

[0105] The block size is set to The two-dimensional matrix Q is divided into a block by rows ; the matrix T is also divided into the same block ; the values in are sorted to obtain ; according to , the data in is scrambled to obtain the encrypted two-dimensional matrix.

[0106] 3) XOR encryption protocol: through 2) to construct the matrix , through the de-identifier to obtain , multiply by a large number , the range is , and is obtained by rounding down

[0107] Its formula is:

[0108]

[0109] Then take the modulus of and 256 to obtain an integer in the range of 0-255

[0110] Its formula is:

[0111]

[0112] Similarly, can be converted into 8-bit binary bytes; finally, the two-dimensional matrix Q and are bitwise XORed; the encrypted two-dimensional matrix is obtained.

[0113] 4) Modulus encryption protocol: through 2) to construct the matrix T , multiply T by a sufficient number , and round down to obtain , whose formula is:

[0114]

[0115] Two-dimensional matrix Q and Summation operation is then performed and modulo operation with 256 is performed to obtain the encrypted two-dimensional matrix;

[0116] The modulo addition operation formula is:

[0117]

[0118] 5) XOR and row-column permutation encryption: first, according to 3), the two-dimensional matrix is encrypted by XOR, and then according to 1), the row-column permutation is performed to obtain the encrypted two-dimensional matrix.

[0119] 6) AES encryption protocol: CFB (Cipher Feedback) mode is adopted. The 128-bit vector of the initialization vector and the 256-bit key are input into the AES function to generate a 128-bit output. Every 16 8-byte integers can be divided into a block , the AES encryption output is XORed with the data block to obtain the encrypted result C . Take C as the new initialization vector to continue encrypting the next data block, and the cycle is repeated until all blocks are encrypted to obtain the encrypted two-dimensional matrix.

[0120] wherein The block method is shown in the following formula:

[0121]

[0122]

[0123] Each block has 16 integers, that is, 128 bytes.

[0124] Fourthly, the encrypted matrix two-dimensional value is converted into a format compatible encrypted 3D model.

[0125] Each value of the encrypted two-dimensional matrix is converted into an 8-bit binary number, then combined into a binary 96-bit matrix, and then according to the IEEE 754 standard, each 32-bit is converted into a real number N, and the conversion formula is as follows:

[0126]

[0127] wherein, m is the binary mantissa part, e is the binary exponent part, s is the binary identifier, usually 0, 1.

[0128] Finally, the encrypted vertex coordinate matrix is formed, and the format is:

[0129]

[0130] The encrypted 3D model is obtained by aggregating the encrypted points and surfaces.

[0131] In summary, the application proposes a 3D model encryption method based on coordinate regularization. First, the vertex coordinate data of the 3D model is obtained, and a coordinate matrix is constructed. The vertex coordinate data is converted into integers in the range of 0-255 through coordinate regularization, and a two-dimensional numerical matrix is constructed. The two-dimensional numerical matrix is encrypted using the substitution-diffusion model and its variants. The encrypted matrix two-dimensional numerical value is converted into vertex data conforming to the 3D model format, forming a format-compatible encrypted 3D model. This method is suitable for 3D data privacy protection in multimedia fields such as industrial manufacturing, medical treatment, and 3D modeling.

[0132] The above is only used to help understand the method of the application and its core essence, but the protection scope of the application is not limited thereto. For those skilled in the art, within the technical scope disclosed by the application, equivalent replacement or change according to the technical solution and inventive concept of the application should be covered within the protection scope of the application. In summary, the content of this specification should not be understood as a limitation of the application.

Claims

1. A 3D model encryption method based on coordinate regularization, characterized in that, Comprise the following steps: S1, obtain the vertex coordinate data of the 3D model, construct the vertex coordinate matrix; The vertex coordinate data of the 3D model is extracted from the storage data of various formats of the 3D model, and the vertex format is: The vertex coordinate matrix is constructed, which is represented as: wherein, P represents a vertex of a 3D model, represents the number of elements in the dataset, contains three elements, namely the Cartesian coordinates of each vertex ; S2, convert the vertex coordinate data into integers in the range of 0-255 by regularization method, and construct a two-dimensional numerical matrix; S201, according to IEEE 754 standard, convert the vertex coordinate floating point number into 32-bit binary number; S202, the coordinate data of each vertex Converted to 32-bit binary form, each vertex gets a 96-bit bit stream; S203, for each vertex coordinate bit stream, convert every 8-bit binary number into decimal number to form 0~255 integer, and form 12 integers through conversion; S204, the converted vertex coordinates are taken as columns, and the number of vertices is taken as rows to form the final two-dimensional matrix Q; The two-dimensional matrix Q is represented as: wherein is the first i is the first j is the first S3, encrypt the two-dimensional numerical matrix by using the permutation-diffusion model and its variants encryption method; S4, convert the encrypted two-dimensional numerical matrix into vertex coordinate data conforming to the format of the 3D model, and form a format compatible encrypted 3D model.

2. The 3D model encryption method based on coordinate regularization according to claim 1, characterized in that, The S3 specifically comprises the following steps: S301, design a key generation method to generate a random sequence; S302, the permutation-diffusion model and its variants encryption method encrypt the two-dimensional numerical matrix using the random sequence.

3. The 3D model encryption method based on coordinate regularization according to claim 2, characterized in that, The S301 is specifically as follows: Generating a secret key by SHA-256 function dividing the secret key into 5 parts: wherein, k i is a 32-bit binary number, , is 128-bit, the first 4 bits are converted into 4 values as 4 parameters of the next pseudo-random function , controls the number of iterations of the pseudo-random function; The pseudo-random function is as follows: The iteration of the pseudo-random function ends, generating two random sequences.

4. The 3D model encryption method based on coordinate regularization according to claim 3, characterized in that, The permutation-diffusion model and its variants in the S302 include six encryption methods, which are row-column permutation encryption, block permutation encryption, XOR diffusion encryption, modulo addition diffusion encryption, XOR and row-column permutation encryption, and AES encryption, and any one of the six encryption methods is used to encrypt the two-dimensional numerical matrix.

5. The 3D model encryption method based on coordinate regularization according to claim 4, characterized in that, The encryption method in the S302 is specifically as follows: S3021, row-column permutation encryption: for the two random sequences, sort the random sequences according to the numerical value, obtain the sorted sequence number as the row index and column index; reorder according to the row and column index, and the reordered two-dimensional matrix is the encrypted two-dimensional matrix; S3022, block permutation encryption: for the two random sequences, select one of the sequences, remap the subscript of the random sequence to form a regularized vector, and organize the vector into a matrix T in row-major manner; The matrix T is: Set the block size to , the two-dimensional matrix Q is Rows are grouped into blocks ; The matrix T is also divided into the same blocks ; By Sort the values ​​in ;according to chaos The data in is obtained to obtain the encrypted two-dimensional matrix; S3023, exclusive or diffusion encryption: the matrix constructed by S3022 , obtained by de-identifier , multiply by , obtained by rounding down , the formula is: wherein is an integer ranging from ; To and 256 modulo operation obtains an integer in the range 0-255 which is expressed in formula as: Similarly, the converted into 8-bit binary bytes; the last two-dimensional matrix Q and performs a bitwise XOR operation; obtains the encrypted two-dimensional matrix; S3024, Modular Diffusion Encryption: Matrix constructed by S3022 T ,Will T Multiply , round down to get , its formula is expressed as: The two-dimensional matrix Q and The summation operation is then performed and modulo 256 operation is performed to obtain the encrypted two-dimensional matrix; the modulo addition operation formula is: S3025, XOR and row-column permutation encryption: first, encrypt the two-dimensional matrix by XOR diffusion encryption according to S3023, and then encrypt the two-dimensional matrix by row-column permutation encryption according to S3021 to obtain the encrypted two-dimensional matrix; S3026, AES encryption: using CFB mode; input the 128-bit vector of initialization vector and 256-bit key into the AES function to generate 128-bit output; divide each 16 8-byte integers into a block , XOR the AES encryption output and the data block to obtain the encrypted result C ; use C as the new initialization vector to continue encrypting the next data block, and sequentially loop until all blocks are encrypted to obtain the encrypted two-dimensional matrix; wherein The block method is shown in the following equation: Each block has 16 integers, that is, 128 bytes.

6. The 3D model encryption method based on coordinate regularization according to any one of claims 2-5, characterized in that, The S4 specifically comprises the following steps: S401, convert each value of the encrypted two-dimensional matrix into 8-bit binary number, and then combine into a binary 96-bit matrix; S402, according to IEEE 754 standard, convert every 32 bits into real number N, and the conversion formula is as follows: wherein, m is a binary significand part, e is a binary exponent part, s is a binary identifier; S403, forming the encrypted vertex coordinate matrix with the format: S404, obtain the encrypted 3D model by aggregating the encrypted points and surfaces.

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