A PDF signature method and system for preventing seal copying

Abstract

The present invention discloses a PDF signature method and system for preventing seal copying, belonging to the technical field of electronic document security, including: obtaining an original electronic contract, configuring its signature field metadata, where the signature field metadata includes the signing order, signatory information, signature field information, and electronic seal pictures of all signatories; performing a transparency processing on each electronic seal picture, and embedding each transparently processed electronic seal picture into the corresponding position of the original electronic contract according to the signature field information to generate a pre-sealed electronic contract; based on the signing order, sequentially delivering the pre-sealed electronic contract to each signatory for digital signature through a chained signing mechanism, and finally outputting a target contract with a complete signature chain. This application can effectively prevent the movement or copying of seals within the preview software of the macOS system, contribute to maintaining the legal effect and security of electronic documents, and enhance users' confidence in the electronic signature system.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic document security, and particularly to a PDF signature method and system for preventing seal copying. Background Art

[0002] Since the Shang and Zhou dynasties, seals have been used as tools for identity verification and document integrity, playing an important role in official documents, commercial contracts, and personal tokens. Their uniqueness and the non-replicable nature of the seal impressions lay the foundation for legal validity. With the development of digitalization, electronic signature technology, based on the public key infrastructure (PKI) and encryption algorithms, binds digital certificates to the signer's identity and combines timestamping to solidify the signing sequence, achieving a modern upgrade of the traditional seal function.

[0003] Currently, electronic signature technology mainly follows international regulations such as eIDAS, and generally adopts the PDF format combined with the PADES (PDF Advanced Electronic Signatures) standard to form a solution that can not only ensure document integrity and consistency but also be recognized by the global judicial system. The mainstream electronic contract platforms in the industry all adopt this standard to achieve cross-platform rendering consistency and establish a security protection mechanism that automatically invalidates the document once it is tampered with.

[0004] However, this solution has obvious security risks in specific operating systems, especially in the macOS environment. The default PDF preview function in macOS treats the signature layer as an independently operable object, allowing users to perform unauthorized operations such as dragging or copying the signature image, which may lead to the legitimate signature being used for forging documents, bypassing digital certificate verification, and thus triggering the risk of identity theft. In addition, any modification to the signature position will damage the original document structure, resulting in hash verification failure and being difficult to be recognized by conventional detection tools. More importantly, there is no log record for such tampering behavior, increasing the difficulty of defining the legal liability subject.

[0005] These problems seriously weaken the security protection ability of the PADES standard, bringing three major crises: legal validity doubts, increased economic fraud risks, and decreased technical trust. Therefore, there is an urgent need for a method that can be compatible with existing standards and does not rely on a specific reader to prevent the illegal use of signature images while ensuring that the user experience is not affected. Summary of the Invention

[0006] The object of the present invention is to provide a PDF signature and seal method and system for preventing seal copying, so as to solve the security problem that the electronic seal directly embedded inside the signature field can be moved and copied at will in the preview software of the macOS system in the prior art, and the problem of poor user experience caused by the frequent prompt that the file has been changed in the electronic contract signature system when multiple signatures are required.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] A PDF signature and seal method for preventing seal copying in the present application includes the following steps:

[0009] Obtain the original electronic contract, and configure the signature field metadata of the original electronic contract, where the signature field metadata includes the signing order, signatory information, signature field information, and the electronic seal pictures of all signatories;

[0010] Perform transparency processing on each electronic seal picture, and embed each transparently processed electronic seal picture into the corresponding position of the original electronic contract according to the signature field information to generate a pre-sealed electronic contract;

[0011] Based on the signing order, sequentially deliver the pre-sealed electronic contract to each signatory for digital signature through a chained signing mechanism, generate an incremental version with hash encapsulation each time a signature is made, and finally output a target contract containing a complete signature chain.

[0012] Preferably, the signatory information includes the account of each signatory and its corresponding digital certificate;

[0013] The signature field information includes the page number, coordinates, width and height where each signature field is located, and the signing status.

[0014] Preferably, embedding each transparently processed electronic seal picture into the corresponding position of the original electronic contract according to the signature field information includes:

[0015] Parse the PDF document tree structure of the page to which the signature field belongs, and obtain the page content stream object corresponding to the signature field;

[0016] Convert the transparently processed electronic seal picture into a PDF standard XObject image object, and set its absolute position and size according to the page number, coordinates, and width and height of the corresponding signature field;

[0017] Write the configured XObject picture object into the page content stream object.

[0018] Preferably, generating the pre-sealed electronic contract includes:

[0019] After inserting all the electronically sealed images after transparency processing into the original electronic contract, call the save method of the PDF writing object to save the PDF page containing the newly inserted images as a new PDF file.

[0020] Preferably, the method further includes:

[0021] Before each signatory performs a digital signature, perform a will authentication operation on it.

[0022] Preferably, the pre-sealed electronic contract is sequentially delivered to each signatory for digital signature through a chained signing mechanism, and each signature generates an incremental version with hash encapsulation, including:

[0023] Send the pre-sealed electronic contract to the first-order signatory;

[0024] After the first-order signatory passes the will authentication, load the pre-sealed electronic contract and create a corresponding signature field for it;

[0025] Perform a hash digest on the PDF file after inserting the signature field, and perform a digital signature on the digest result according to the digital certificate of the first-order signatory;

[0026] Add the signature result to the signature field of the PDF file to form the first signed contract, and update the signature field status to signed;

[0027] Send the first signed contract to the second-order signatory for digital signature, and repeat the above steps until all signatories have completed signing.

[0028] Preferably, after creating the corresponding signature field, it further includes:

[0029] Set the absolute position and size of the signature field according to the signature field information included in the signature field metadata, and set the appearance of the signature field to be transparent.

[0030] A PDF signature and seal system for preventing seal copying, including:

[0031] A setting module for obtaining the original electronic contract and configuring the signature field metadata of the original electronic contract, where the signature field metadata includes the signing order, signatory information, signature field information, and the electronically sealed images of all signatories;

[0032] A contract processing module for performing transparency processing on each electronically sealed image and embedding each transparently processed electronically sealed image into the corresponding position of the original electronic contract according to the signature field information to generate a pre-sealed electronic contract;

[0033] A contract signing module, which is used to sequentially deliver the pre-stamped electronic contract to each signatory for digital signature through a chained signing mechanism based on the signing order. Each signature generates an incremental version with hash encapsulation, and finally outputs a target contract containing a complete signature chain.

[0034] An electronic device includes a memory and a processor. The memory is used to store one or more computer instructions. Among them, the one or more computer instructions are executed by the processor to implement a PDF signature method for preventing seal copying as described in any one of the above.

[0035] A computer-readable storage medium storing a computer program, where the computer program causes a computer to implement a PDF signature method for preventing seal copying as described in any one of the above when executed.

[0036] The present invention has the following beneficial effects:

[0037] Without violating the PDF signature standard, it can effectively prevent moving or copying seals in the preview software of the macOS system. This not only helps to maintain the legal effect and security of electronic documents, but also enhances users' confidence in the electronic signature system, and can promote the wide application of electronic contracts and digital signatures. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0039] Figure 1 It is a flowchart of a PDF signature method for preventing seal copying provided by an embodiment of the present application;

[0040] Figure 2 It is a schematic structural diagram of a PDF signature system for preventing seal copying provided by an embodiment of the present application;

[0041] Figure 3 It is a schematic diagram of an electronic device for implementing a PDF signature method for preventing seal copying provided by an embodiment of the present application. Detailed Embodiments

[0042] To make the technical solution of this application clearer, the following further elaborates on the present invention in conjunction with the accompanying drawings and specific embodiments. The terms "first", "second", etc. in the claims and the description of this application are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances. This is merely a way of distinguishing objects with the same attributes when describing the embodiments of this application. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, so that a process, method, system, product, or device including a series of units does not have to be limited to those units, but may include other units that are not clearly listed or are inherent to these processes, methods, products, or devices.

[0043] Embodiment 1

[0044] As Figure 1 shown, a PDF signature method for preventing seal copying includes the following steps:

[0045] S110. Obtain the original electronic contract and configure the signature field metadata of the original electronic contract. The signature field metadata includes the signing order, signatory information, signature field information, and the electronic seal pictures of all signatories;

[0046] S120. Perform transparency processing on each electronic seal picture, and embed each transparently processed electronic seal picture into the corresponding position of the original electronic contract according to the signature field information to generate a pre-stamped electronic contract;

[0047] S130. Based on the signing order, sequentially deliver the pre-stamped electronic contract to each signatory through a chained signing mechanism for digital signature. Each signature generates an incremental version with hash encapsulation, and finally outputs a target contract containing a complete signature chain.

[0048] In this embodiment, the initiator of the signing process first logs in to the electronic signature system to create a signing process.

[0049] Specifically, the initiator of the signing process uploads the original electronic contract to the electronic signature system and sets the signature information. Signature information generally refers to the marking information used to confirm the authenticity, integrity, and identity of the signatory in documents, contracts, agreements, or other legal documents. In this embodiment, each signature information is a signature field metadata (SignatuteMeta). The signature field metadata is a series of additional information related to digital signatures embedded in the electronic document, used to describe key details such as the generation environment of the signature, the identity of the signatory, the signature time, and the signature algorithm. It is usually bound to the signature field (Signature Field) and is an important part of the signature object.

[0050] In this embodiment, the signature field metadata includes the signing order, the account of each signatory and the visual appearance picture of the corresponding digital certificate electronic seal, as well as the signature field information. The signature field information specifically includes the page number, coordinates, width and height, and signing status of each signature field. Among them, the signing order is used to specify the order of signing for each signature field; the account of the signatory and its digital certificate are used for subsequent identity verification and signature operations; the page number and coordinates of the signature field are used to specify the position of the signature field on the PDF page, specifically including the page number (Page), the horizontal coordinate X, and the vertical coordinate Y; the signing status is used to indicate the status of the signature field. For example, before signing, its status is set to "to be signed", and after signing is completed, its status will be updated to "signed". Then, the signature field metadata is saved to the database, and these metadata are associated with the current signing process for subsequent processing.

[0051] The electronic signature system loads and reads the original electronic contract PDF file uploaded by the signing process initiator. This can be done through the PdfReader class, which is responsible for reading the content of the PDF file and providing access to the pages. Then, a new PDF writing object is created through a PDF processing library such as the PdfStamper class of iText. This object allows modification and addition of content based on the original PDF document. Then, the pages are processed and the electronic seal picture is inserted.

[0052] Furthermore, the PDF document tree structure of the page to which the signature field belongs is parsed to obtain the page content stream object corresponding to the signature field;

[0053] The electronically signed picture after transparency processing is converted into a PDF standard XObject image object, and its absolute position and size are set according to the corresponding signature field coordinates and width and height;

[0054] The configured XObject picture object is written into the page content stream object.

[0055] Specifically, determine the page where the signature field should exist based on the signature field information, that is, the page where the electronic seal image needs to be inserted. First, obtain the page object (PdfPage) of the specified page number through the getPage(int pageNumber) method of the PdfDocument object in the PDF processing library such as iText. It should be noted that the pageNumber parameter here starts from 1, that is, the page number of the first page is 1, the page number of the second page is 2, and so on. Then, call the getOverContent() method of the PdfStamper class to obtain the PdfContentByte object from the page object. This object is used to draw or write additional content on the specified page. Here, it should be noted that the page content stream is one of the core parts of the PDF document because it determines the specific presentation of the page. Whether it is static text, dynamically generated content, or embedded images, their positions, styles, and other properties need to be defined through the page content stream. In the iText library, the PdfContentByte object is an abstract representation of the page content stream. It provides a convenient interface for users to directly add drawing instructions to the PDF page without having to manually write the underlying PDF content stream syntax.

[0056] Next, use image processing technology to make the visual image of the electronic seal transparent. For example, the JAVA native BufferedImage class can be used to process the image, and transparency can be achieved by modifying the Alpha channel (transparency channel) of the image to avoid obscuring the text in the PDF. Then, convert the data of the transparent image into a PDF image XObject object. In PDF terms, XObject is used to represent images or other forms of data independent of the page content. When adding a picture to a PDF, a picture XObject object needs to be created first, and then the absolute coordinate position (X, Y) of the picture object in the PdfPage and the width (Width) and height (Height) of the picture are set according to the coordinates and dimensions of the corresponding signature field. Finally, the picture XObject is inserted into the PdfContentByte object to complete the drawing of the picture on the PDF page. Repeat the above steps to process all the signature field metadata in sequence and insert all the electronic seal images into the PDF.

[0057] Furthermore, after inserting all the transparent electronic seal images into the original electronic contract, call the save method of the PDF writing object to save the PDF page containing the newly inserted images as a new PDF file.

[0058] After completing the editing of all pages that will have signature fields, call the save method of the PDF writing object, such as the close() method of PdfStamper, to save the PDF pages containing the newly inserted pictures as a new PDF file. This new PDF file is the actual electronic contract to be signed, that is, the electronic contract to be signed. In this embodiment, it is also referred to as the pre-signed electronic contract.

[0059] The essence of this step is to pre-insert all the electronic seals involved in the signing process into the specified signature positions for pre-stamping. In this way, all the electronic seals will exist as part of the content in the PDF document, so that even in the preview software of the macOS system, the seals cannot be moved or copied casually, thus ensuring the authenticity and integrity of the electronic contract.

[0060] Then, according to the settings of the signing process, notify each signatory to sign in the signing order. The notification content includes the link to the electronic contract to be signed. In this embodiment, it is implemented through a chained signing mechanism, that is, first notify the first signatory in the signing order to sign.

[0061] Among them, the chained signing mechanism is a method to ensure that an electronic contract is digitally signed by multiple signatories in a predetermined order. Each signature will generate an incremental updated version with a hash encapsulation (that is, including the hash value of the previous version), and update the status of the signature field until all signatories complete the signature, and then output the target contract with a complete digital signature chain.

[0062] Exemplarily, the signing order is A -> B -> C. According to the chained signing mechanism, first send the electronic contract to be signed to A for signature. After A completes the signature, a file E containing A's signature is generated. Then send file E to B for signature. After B receives file E and completes the signature, a file F containing A's and B's signatures is generated; then send file F to C for signature. After C receives file F and completes the signature, the target signed contract containing A, B, and C's signatures is generated.

[0063] Furthermore, send the pre-signed electronic contract to the first signatory;

[0064] After the first signatory passes the will authentication, load the pre-signed electronic contract and create a corresponding signature field for it;

[0065] Perform a hash digest on the PDF file after inserting the signature field, and digitally sign the digest result according to the digital certificate of the first signatory;

[0066] Add the signature result to the signature field of the PDF file to form the first signed contract, and update the status of the signature field to signed;

[0067] Send the first signed contract to the second signatory for digital signature, and repeat the above steps until all signatories have completed signing.

[0068] The first signatory clicks on the link to be signed to log in to the electronic signature system for preview of the electronic contract. If they agree to sign the electronic contract, first perform the signatory's intention authentication. In this embodiment, the way of intention authentication can be face swiping, SMS verification, or email verification code verification, that is, there is no restriction on the specific authentication method, which can be determined according to actual needs.

[0069] After the intention authentication is passed, perform the signing of the electronic contract. In this embodiment, the signing of the electronic contract follows the PADES signature standard of PDF.

[0070] Specifically, load the pre-signed electronic contract, create a signature field, set the page number (PageNumber), coordinates (X, Y), width (Width), and height (Height) of the signature field according to the signature field metadata, and set the appearance of the signature field to a transparent PNG. Essentially, it is to insert a transparent signature field at the position where the electronic seal picture is inserted, perform a digest on the PDF after inserting the signature field, and digitally sign the digest with the digital certificate of the current signatory, then add the signature result to the place where the signature result is placed in the signature field, and at the same time modify the status of the signature field to signed.

[0071] Then send the electronic contract signed by the first signatory to the second signatory for signing through the link, that is, the PDF electronic contract signed this time is the contract to be signed by the next signatory. For example, after the first signatory signs and forms the signed document A, the second signatory signs the signed document A.

[0072] After each signatory signs, a new PDF containing the current signature is generated, ensuring that each signature is independent and valid, avoiding the occurrence of the prompt "The file has been changed" during the multiple signature process, and improving the user experience and the security of the signature.

[0073] Repeat the above process until the status of all signature fields is signed, that is, all signatories have completed signing in the signing order, and mark this signing process as completed.

[0074] This embodiment can effectively prevent the movement or copying of the seal within the preview software of the macOS system without violating the PDF signature standard. This not only helps to maintain the legal effect and security of electronic documents, but also enhances users' confidence in the electronic signature system, and can promote the wide application of electronic contracts and digital signatures.

[0075] Embodiment 2

[0076] As shown in Figure 2 Figure , a PDF signature system for preventing seal copying includes:

[0077] A setting module for obtaining an original electronic contract and configuring signature field metadata of the original electronic contract. The signature field metadata includes signing order, signatory information, signature field information, and electronic seal pictures of all signatories;

[0078] A contract processing module for performing transparency processing on each electronic seal picture and embedding each transparently processed electronic seal picture into the corresponding position of the original electronic contract according to the signature field information to generate a pre-sealed electronic contract;

[0079] A contract signing module for sequentially delivering the pre-sealed electronic contract to each signatory for digital signature through a chained signing mechanism based on the signing order. Each signature generates an incremental version with hash encapsulation, and finally outputs a target contract containing a complete signature chain.

[0080] This embodiment is used to implement the method provided in the above embodiment and has the corresponding beneficial effects of the above method. For technical details not described in detail in this embodiment, reference can be made to the methods provided in all the foregoing embodiments of the present invention.

[0081] Embodiment 3

[0082] As shown in Figure 3 Figure , an electronic device includes a memory 301 and a processor 302. The memory 301 is used to store one or more computer instructions. Among them, the one or more computer instructions are executed by the processor 302 to implement the above-mentioned PDF signature method for preventing seal copying.

[0083] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working process of the above-described electronic device can refer to the corresponding process in the foregoing method embodiment and will not be elaborated herein.

[0084] A computer-readable storage medium storing a computer program, and the computer program, when executed by a computer, implements the above-mentioned PDF signature method for preventing seal copying.

[0085] Exemplarily, the computer program can be divided into one or more modules / units. One or more modules / units are stored in the memory 301 and executed by the processor 302, and the input / output (I / O) interface transmission of data is completed by the input interface 305 and the output interface 306 to complete the present invention. One or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and the instruction segments are used to describe the execution process of the computer program in the computer device.

[0086] The computer device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The computer device may include, but is not limited to, a memory 301 and a processor 302. Those skilled in the art can understand that this embodiment is only an example of the computer device, and does not constitute a limitation on the computer device. It may include more or fewer components, or combine certain components, or different components. For example, the computer device may also include an input device 307, a network access device, a bus, etc.

[0087] The processor 302 can be a Central Processing Unit (CPU), or other general-purpose processors 302, Digital Signal Processors (DSPs) 302, Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor 302 can be a microprocessor 302 or the processor 302 can also be any conventional processor 302, etc.

[0088] The memory 301 can be an internal storage unit of the computer device, such as the hard disk or memory of the computer device. The memory 301 can also be an external storage device of the computer device, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. equipped on the computer device. Further, the memory 301 can also include both the internal storage unit and the external storage device of the computer device. The memory 301 is used to store computer programs and other programs and data required by the computer device. The memory 301 can also be used to temporarily store in the output device 308, and the aforementioned storage media include various media such as USB flash drives, mobile hard disks, read-only memory ROM 303, random access memory RAM 304, diskettes, or optical discs that can store program codes.

[0089] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A PDF signature method for preventing seal copying, characterized in that, It includes the following steps: Obtain the original electronic contract and configure the signature field metadata of the original electronic contract, where the signature field metadata includes the signing order, signatory information, signature field information, and the electronic seal pictures of all signatories; Perform transparency processing on each electronic seal picture, and embed each transparently processed electronic seal picture into the corresponding position of the original electronic contract according to the signature field information to generate a pre-sealed electronic contract; Based on the signing order, sequentially deliver the pre-sealed electronic contract to each signatory for digital signature through a chained signing mechanism. Create a transparent signature field covering the transparent electronic seal picture before each signature, and perform a hash digest on the page where the signature field is located. Generate an incremental version with hash encapsulation for each signature, and finally output the target contract with a complete signature chain; Among them, embedding each transparently processed electronic seal picture into the corresponding position of the original electronic contract according to the signature field information includes: Parse the PDF document tree structure of the page to which the signature field belongs, and obtain the page content stream object corresponding to the signature field; Convert the transparently processed electronic seal picture into a PDF-standard XObject image object, and set its absolute position and size according to the page number, coordinates, width, and height of the corresponding signature field; Write the configured XObject picture object into the page content stream object.

2. The PDF signature method for preventing seal copying according to claim 1, wherein The signatory information includes the account number of each signatory and its corresponding digital certificate; The signature field information includes the page number, coordinates, width, height, and signing status of each signature field.

3. A PDF signature method for preventing seal copying according to claim 2, characterized in that, Generating the pre-sealed electronic contract includes: After inserting all the transparently processed electronic seal pictures into the original electronic contract, call the save method of the PDF writing object to save the PDF page containing the newly inserted pictures as a new PDF file.

4. A PDF signature method for preventing seal copying according to claim 2, characterized in that, The method further includes: Before each signatory performs a digital signature, perform a willingness authentication operation on it.

5. A PDF signature method for preventing seal copying according to claim 4, characterized in that, Sequentially delivering the pre-sealed electronic contract to each signatory for digital signature through a chained signing mechanism, and generating an incremental version with hash encapsulation for each signature includes: Send the pre-sealed electronic contract to the first-order signatory; After the first-order signatory passes the willingness authentication, load the pre-sealed electronic contract and create a corresponding signature field for it; Perform a hash digest on the PDF file after inserting the signature field, and perform a digital signature on the digest result according to the digital certificate of the first-order signatory; Add the signature result to the signature field of the PDF file to form the first signed contract, and update the signature field status to signed; Send the first signed contract to the second-order signatory for digital signature, and repeat the above steps until all signatories have completed signing.

6. A PDF signature method for preventing seal copying according to claim 5, characterized in that, After creating the corresponding signature field, it further includes: Set the absolute position and size of the signature field according to the signature field information included in the signature field metadata, and set the appearance of the signature field to transparent.

7. A PDF signature system for preventing seal copying, characterized in that, It includes: A setting module for obtaining an original electronic contract and configuring signature field metadata of the original electronic contract, where the signature field metadata includes a signing order, signatory information, signature field information, and electronic seal images of all signatories; A contract processing module for performing transparency processing on each electronic seal image and embedding each transparently processed electronic seal image into a corresponding position of the original electronic contract according to the signature field information to generate a pre-sealed electronic contract; A contract signing module for sequentially delivering the pre-sealed electronic contract to each signatory for digital signature through a chained signing mechanism based on the signing order, creating a transparent signature field covering the transparent electronic seal image before each signature, performing a hash digest on the page where the signature field is located, generating an incremental version with hash encapsulation for each signature, and finally outputting a target contract with a complete signature chain; Among them, the contract processing module embedding each transparently processed electronic seal image into a corresponding position of the original electronic contract according to the signature field information includes: Parsing the PDF document tree structure of the page to which the signature field belongs to obtain a page content stream object corresponding to the signature field; Converting the transparently processed electronic seal image into a PDF-standard XObject image object and setting its absolute position and size according to the page number, coordinates, and width and height of the corresponding signature field; Writing the configured XObject image object into the page content stream object.

8. An electronic device, characterized in that, It includes a memory and a processor, where the memory is used to store one or more computer instructions, and the one or more computer instructions are executed by the processor to implement a PDF signature method for preventing seal copying as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, The computer program, when executed by a computer, implements a PDF signature method for preventing seal copying as described in any one of claims 1 to 6.

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