Robust watermarking method for authenticating authenticity of 3D printing model

Abstract

The invention provides a robust watermarking method for authenticating authenticity of a 3D printing model, which comprises a registration stage and a verification stage, and is characterized in that robust watermarking design and embedding of the 3D printing model are completed in the registration stage, and authentication of the 3D printing model is completed in the verification stage; according to the method, authentication information is converted into a binary bit string, and embedded binary bit watermark information is formed with the assistance of a verification data string and a positioning flag bit; selecting an area in which the watermark is embedded in the model; the joint structure in the printing process serves as a watermark carrier, the moving direction of a printer nozzle in an embedding area is modified according to watermark information, and embedding of the watermark information is achieved; and the watermark position in the model entity is positioned through the target detection network, and watermark information is extracted to judge the authenticity of the model. According to the method, the integrity of a model entity can be ensured in the process of authenticating the authenticity of the 3D printing model, the watermark is simple to embed and extract, the detection result is excellent, the anti-attack capability is high, and the robustness is high; and authentication cost is low and practicality is high.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to a robust watermark method for authenticating the authenticity of a 3D printed model. Background Art

[0002] As a rapid prototyping manufacturing technology, 3D printing has unparalleled advantages over traditional manufacturing in terms of designing object appearance, manufacturing speed, precision and material selection. 3D printing has been widely used in fields such as healthcare, automobile manufacturing and aerospace. With the development of 3D printing technology and the reduction of costs, it has become possible to use this technology to imitate products. Due to the characteristics of 3D printed models in physical form and manufacturing process, malicious users have brought challenges to law enforcement by counterfeiting products through reverse engineering. Therefore, the intellectual property protection and anti-counterfeiting certification of 3D printed models are crucial.

[0003] At present, some methods for authenticating the authenticity of 3D printed models have been proposed, most of which are authenticated by embedding watermarks. According to the source of the embedded watermark, it can be divided into authentication methods using exogenous watermarks and authentication methods using traces in the printing process as watermarks. Although these methods have certain authentication capabilities, they have certain disadvantages in terms of the security of embedded watermarks, the complexity of authentication schemes, and the cost of authentication. It is difficult to take both into account at the same time, and it is difficult to promote and apply them. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a robust watermark method for authenticating the authenticity of a 3D printed model. The present invention has the ability to efficiently authenticate the authenticity of a model, and can embed a watermark into a model and extract a watermark from a model in a simple manner. In addition, the robustness of the watermark can be improved.

[0005] The technical solution of the present invention is: a robust watermark method for authenticating the authenticity of a 3D printed model, comprising a registration phase and a verification phase, wherein the registration phase completes the robust watermark design and embedding of the 3D printed model, and the verification phase completes the authentication of the 3D printed model;

[0006] The registration phase includes the following steps:

[0007] S1), construct watermark information;

[0008] S2), performing slicing operation on the digital model to be printed;

[0009] S3), embedding watermark information into the digital model to be printed after the slicing operation;

[0010] S4), printing the digital model embedded with watermark information to obtain a model entity containing authentication watermark information;

[0011] S5), using the target detection network to detect the model entity and determine the authenticity of the entity model;

[0012] The verification phase includes the following steps:

[0013] A1), after obtaining the model entity to be inspected, searching for the existence of a joint structure at the corresponding position of the model entity according to the joint structure image retained in the dedicated model authentication database;

[0014] If it exists, then go to step A2), otherwise, the model entity to be checked is a forged model;

[0015] A2), using the same method and equipment as in step S6) of the registration phase to photograph the seam structure of the model entity to be inspected, and then input the image into the trained target detection network to identify and extract the watermark;

[0016] A3) Check the extracted watermark information and divide the complete watermark information according to the first and last positioning marks and the empty mark;

[0017] A4) The binary bit string containing the authentication information is reversely converted into authentication information by the method of step S1) in the registration phase, and matched with the authentication information pre-stored in the dedicated model authentication database. If the match is successful, the model entity can be identified as a genuine model, otherwise it is identified as a counterfeit model.

[0018] Preferably, in step S1), the authentication information is converted into a binary bit string, and the embedded binary bit watermark information is formed by the verification data string and the positioning flag.

[0019] Preferably, in step S1), constructing watermark information specifically includes the following steps:

[0020] S11), converting the authentication information into a binary bit string, and obtaining a cyclic redundancy check code by performing a cyclic redundancy check code calculation on the binary bit string;

[0021] S12), performing a parity check on the cyclic redundancy check code to obtain a parity check bit; and sequentially splicing the binary bit string, the cyclic redundancy check code, and the parity check bit;

[0022] S13), adding a positioning flag bit '1' and a null flag bit to the beginning of the binary bit string;

[0023] S14), adding a null mark and a positioning mark '0' at the end of the parity bit to form a complete embedded watermark information, and saving the embedded watermark information in the model authentication database.

[0024] Preferably, in step S12), the splicing is to append a cyclic redundancy check code to the end of the bit string; and to append a parity check result of the cyclic redundancy check code to the end of the CRC-5 check code.

[0025] Preferably, in step S2), the slicing operation is performed on the digital model to be printed, which specifically includes the following steps:

[0026] S21), importing the digital model to be printed into the slicing software, adjusting the placement of the digital model, selecting the location of the joint structure on the inner side of the digital model, and marking it;

[0027] S22), the digital model that has been set is sliced ​​by slicing software to generate a G-code file.

[0028] Preferably, in step S21), the number of layers of the selected seam structure is greater than the number of embedded watermark information.

[0029] Preferably, in step S21), during the embedding process, the head end of the watermark information corresponds to the low-order printing layer of the digital model, and the tail end of the watermark information corresponds to the high-order printing layer of the digital model.

[0030] Preferably, in step S21), the G-code code segment of the outermost circle of the printing layer corresponding to the seam structure area marked in step S21) is adjusted, specifically:

[0031] When the embedded watermark information bit is '1', the G-code is sorted in reverse order, so that the printer nozzle moves in the opposite direction to the original setting direction when printing the outermost circle;

[0032] When the embedded watermark information bit is '0', the execution order of the G-code code segment of this segment is maintained, and the moving direction of the printer nozzle is maintained in the outermost circle;

[0033] When the embedded watermark information bit is empty, the original moving direction is maintained, the starting and ending coordinates of the G-code code segment are set at the edge of the model, and the coordinates of each step of the code are adjusted according to the model contour.

[0034] Preferably, in step S3), the G-code code segment at the seam structure is adjusted according to the embedded watermark information to complete the embedding of the watermark information and save it as a G-code code file to be printed.

[0035] Preferably, in step S4), the G-code file to be printed is input into a 3D printer for printing to obtain a model entity containing authentication watermark information.

[0036] Preferably, in step S5), an image of the internal joint structure of the model entity is obtained, and detection is performed through a target detection network. The detection result is analyzed and compared with the original authentication information to determine the authenticity of the model entity.

[0037] Preferably, in step S6), the target detection network adopts the YOLOv10 target detection network.

[0038] Preferably, in step A3), the verification of the watermark information specifically includes the following steps:

[0039] A31), dividing the watermark sequence segment, cyclic redundancy check code segment, and parity check bit of the authentication information;

[0040] A32), using the parity check bit to perform parity check on the cyclic redundancy check code;

[0041] A33) Use the verified cyclic redundancy check code to verify the binary bit string containing the authentication information. Only after both verifications pass can we proceed to step A4), otherwise the model entity is judged to be a forged model.

[0042] The beneficial effects of the present invention are:

[0043] 1. The present invention is divided into two parts: the registration phase and the verification phase. The registration phase completes the robust watermark design and embedding of the 3D printing model, and the verification phase completes the authentication of the 3D printing model.

[0044] 2. The present invention can ensure the integrity of the model entity in the process of authenticating the authenticity of the 3D printed model. The watermark embedding and extraction methods are simple, the detection results are excellent, the anti-attack ability is strong, and the robustness is high. The authentication method is low-cost and highly practical.

[0045] 3. The present invention utilizes the change in the moving direction of the printer nozzle to embed watermark information, and the anti-attack performance of the watermark carrier is enhanced;

[0046] 4. The present invention uses a trained target detection model to locate and extract watermarks for images containing seam structures, thereby ensuring the authentication effect and reducing the complexity and cost of authentication. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0048] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0049] like Figure 1As shown, this embodiment provides a robust watermark method for authenticating the authenticity of a 3D printed model, including a registration phase and a verification phase, wherein the registration phase includes the following steps:

[0050] S1) Construct watermark information

[0051] This embodiment converts the authentication information into a binary bit string, and uses the verification data string and the positioning flag bit to form the embedded binary bit watermark information; specifically, the following steps are included:

[0052] S11), obtaining a cyclic redundancy check code by performing cyclic redundancy check code calculation on the binary bit string;

[0053] S12), performing a parity check on the cyclic redundancy check code to obtain a parity check bit; and sequentially splicing the binary bit string, the cyclic redundancy check code, and the parity check bit; wherein the splicing is to attach the cyclic redundancy check code to the end of the bit string; and calculating the parity check result of the cyclic redundancy check code and attaching it to the end of the CRC-5 check code;

[0054] S13), adding a positioning flag bit '1' and a null flag bit to the beginning of the binary bit string;

[0055] S14), adding a null mark and a positioning mark '0' at the end of the parity bit to form a complete embedded watermark information, and saving the embedded watermark information in the model authentication database.

[0056] S2) Slice the digital model to be printed

[0057] S21), importing the digital model to be printed into the slicing software, adjusting the placement of the digital model, and setting appropriate printing parameters, then selecting the location of the joint structure on the inner side of the digital model and marking it. In this embodiment, the number of layers marked on the joint structure should be greater than the length of the complete watermark sequence to be embedded;

[0058] S22), the digital model that has been set is sliced ​​by slicing software to generate a G-code file.

[0059] S3), adjusting the G-code code segment at the seam structure according to the embedded watermark information, completing the embedding of the watermark information, and saving it as a G-code code file to be printed;

[0060] In this embodiment, the head end of the watermark information corresponds to the low-order printing layer of the digital model, and the tail end of the watermark information corresponds to the high-order printing layer of the digital model. And the G-code code segment of the outermost circle of the printing layer corresponding to the seam structure area marked in step S21) is adjusted; when the embedded watermark information bit is '1', the G-code code segment is reversed, so that the movement direction of the printer nozzle when printing the outermost circle is opposite to the original set direction;

[0061] When the embedded watermark information bit is '0', the execution order of the G-code code segment of this segment is maintained, and the moving direction of the printer nozzle is maintained in the outermost circle;

[0062] When the embedded watermark information bit is empty, the original moving direction is maintained, the starting and ending coordinates of the G-code code segment are set at the edge of the model, and the coordinates of each step of the code are adjusted according to the model contour.

[0063] S4), inputting the G-code file to be printed into the 3D printer for printing, and obtaining a model entity containing authentication watermark information;

[0064] S5), obtaining an image of the internal seam structure of the model entity, and detecting it through a target detection network, parsing the detection result and comparing it with the original authentication information to determine the authenticity of the model entity; this embodiment adopts the YOLOv10 target detection network, which is trained with a large number of images of the seam structure of the real printed model, and can accurately identify the seam structure of the real model and extract the watermark information embedded therein.

[0065] In this embodiment, the verification phase includes the following steps:

[0066] A1), after obtaining the model entity to be inspected, searching for the existence of a joint structure at the corresponding position of the model entity according to the joint structure image retained in the dedicated model authentication database;

[0067] If it exists, then go to step A2), otherwise, the model entity to be checked is a forged model;

[0068] A2), using the same method and equipment as in step S6) of the registration phase to photograph the seam structure of the model entity to be inspected, and then input the image into the trained target detection network to identify and extract the watermark;

[0069] A3) Check the extracted watermark information and divide the complete watermark information according to the first and last positioning marks and the empty mark; specifically, the following steps are included:

[0070] A31), dividing the watermark sequence segment, cyclic redundancy check code segment, and parity check bit of the authentication information;

[0071] A32), using the parity check bit to perform parity check on the cyclic redundancy check code;

[0072] A33) Use the verified cyclic redundancy check code to verify the binary bit string containing the authentication information. Only after both verifications pass can we proceed to step A4), otherwise the model entity is judged to be a forged model.

[0073] A4) The binary bit string containing the authentication information is reversely converted into authentication information by the method of step S1) in the registration phase, and matched with the authentication information pre-stored in the dedicated model authentication database. If the match is successful, the model entity can be identified as a genuine model, otherwise it is identified as a counterfeit model.

[0074] It can be seen from Tables 1 and 2 that the watermark designed by the method of this embodiment has high robustness and a high authentication success rate of the detection method, among which:

[0075] Table 1 shows the authentication success rate of the detection method under different parameter settings for the digital model

[0076]

[0077]

[0078] Table 2 The success rate of authentication after attacking and destroying the watermark on the inner side of the digital model

[0079]

[0080] The above embodiments and descriptions are only for illustrating the principles and best embodiments of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, all of which fall within the scope of the present invention to be protected.

Claims

1. A robust watermarking method for authenticating the authenticity of a 3D printed model, characterized in that: It includes a registration phase and a verification phase. The registration phase completes the robust watermark design and embedding of the 3D printing model, and the verification phase completes the authentication of the 3D printing model. The registration phase includes the following steps: S1), construct watermark information; S2), performing slicing operation on the digital model to be printed; S3), embedding watermark information into the digital model to be printed after the slicing operation; S4), printing the digital model embedded with watermark information to obtain a model entity containing authentication watermark information; S5), using the target detection network to detect the model entity and determine the authenticity of the entity model; The verification phase includes the following steps: A1) obtaining a model entity to be inspected, and searching for a joint structure at a corresponding position of the model entity; If it exists, then go to step A2), otherwise, the model entity to be checked is a forged model; A2) photographing the joint structure of the model entity to be inspected, and then inputting the image into the trained target detection network for watermark recognition and extraction; A3) Check the extracted watermark information and divide the complete watermark information according to the first and last positioning marks and the empty mark; A4) Reversely convert the binary bit string containing the authentication information into the authentication information, and match it with the authentication information pre-stored in the dedicated model authentication database. If the match is successful, the model entity can be identified as a genuine model, otherwise it can be identified as a counterfeit model.

2. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 1, characterized in that: In step S1), the authentication information is converted into a binary bit string, and the embedded binary bit watermark information is formed by the verification data string and the positioning flag.

3. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 2, characterized in that: Step S1) specifically includes the following steps: S11), obtaining a cyclic redundancy check code by performing cyclic redundancy check code calculation on the binary bit string; S12), performing a parity check on the cyclic redundancy check code to obtain a parity check bit; and sequentially splicing the binary bit string, the cyclic redundancy check code, and the parity check bit; S13), adding a positioning flag bit '1' and a null flag bit to the beginning of the binary bit string; S14), adding a null mark and a positioning mark '0' at the end of the parity bit to form a complete embedded watermark information, and saving the embedded watermark information in the model authentication database.

4. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 3, characterized in that: In step S12), the splicing is to add the cyclic redundancy check code to the end of the bit string; The parity check result of the cyclic redundancy check code is added to the end of the CRC-5 check code.

5. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 1, characterized in that: In step S2), the digital model to be printed is sliced; specifically, the following steps are included: S21), importing the digital model to be printed into the slicing software, adjusting the placement of the digital model, selecting the location of the joint structure on the inner side of the digital model, and marking it; S22), the digital model that has been set is sliced ​​by slicing software to generate a G-code file.

6. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 5, characterized in that: In step S3), the watermark information is embedded into the digital model to be printed after the slicing operation, specifically: S31), adjusting the G-code code segment at the seam structure according to the embedded watermark information, completing the embedding of the watermark information, and saving it as a G-code code file to be printed.

7. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 6, characterized in that: In step S31), during the embedding process, the head end of the watermark information corresponds to the low-order printing layer of the digital model, and the tail end of the watermark information corresponds to the high-order printing layer of the digital model.

8. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 7, characterized in that: In step S31), the G-code code segment of the outermost circle of the printing layer corresponding to the seam structure area marked in step S21) is adjusted.

9. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 8, characterized in that: In step S31), when the embedded watermark information bit is '1', the G-code code is sorted in reverse order, so that the printer nozzle moves in the opposite direction to the original set direction when printing the outermost circle; When the embedded watermark information bit is '0', the execution order of the G-code code segment of this segment is maintained, and the moving direction of the printer nozzle is maintained in the outermost circle; When the embedded watermark information bit is empty, the original moving direction is maintained, the starting and ending coordinates of the G-code code segment are set at the edge of the model, and the coordinates of each step of the code are adjusted according to the model contour.

10. A robust watermark method for authenticating the authenticity of a 3D printed model according to claim 1, characterized in that: In step A3), the verification of the watermark information specifically includes the following steps: A31), dividing the watermark sequence segment, cyclic redundancy check code segment, and parity check bit of the authentication information; A32), using the parity check bit to perform parity check on the cyclic redundancy check code; A33) Use the verified cyclic redundancy check code to verify the binary bit string containing the authentication information. Only after both verifications pass can we proceed to step A4), otherwise the model entity is judged to be a forged model.

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