Copyright protection and traceability method based on physical unclonable function watermark and blockchain

Abstract

The present invention belongs to the field of blockchain technology and relates to a copyright protection and traceability method based on a physical unclonable function watermark and blockchain. The method comprises: a PUF device registration step: constructing a PUF device and generating a device fingerprint through a challenge-response mechanism; registering the device fingerprint on the blockchain and generating a public-private key pair; and a copyright registration step: using a certified PUF device to submit a hash summary of a digital media file to the blockchain to create a copyright identifier. The present invention leverages the characteristics of a physical unclonable function to provide a method for generating a unique key for embedded devices, thereby embedding a physical unclonable function watermark for each digital media stored in the embedded device, thereby achieving the physical ownership of copyright. Registering the PUF device on the blockchain ensures the authenticity of the information of both parties in the copyright transfer process, thereby preventing identity forgery and achieving traceability on the blockchain in combination with a secure digital watermark extraction process.

Description

Technical Field

[0001] The present invention belongs to the field of blockchain technology and relates to a copyright protection and traceability method based on a physical unclonable function watermark and blockchain. Background Art

[0002] In recent years, the development of digital media technology has become a focal point. This innovation has prompted copyright holders and creators to enter the new media sector, further promoting information dissemination. Consequently, the issue of digital media copyright protection has become increasingly prominent. With increasing awareness of copyright, providing the public with reliable proof of copyright ownership and a traceable copyright transfer process has become a key factor in promoting the healthy development of digital media technology. Digital watermarking technology is commonly used to protect digital media copyright by confirming ownership and preventing unauthorized use. However, without reliable third-party oversight, these methods pose the risk of security vulnerabilities in the watermark extraction process. Furthermore, the lack of tangible ownership attributes of digital media poses challenges to secure copyright transfer and traceability.

[0003] Based on the Kerckhoff principle, everything in a modern cryptographic system, except the key, should be known. However, for most embedded devices, attackers have physical access to the integrated circuit, making the key encapsulated in the non-volatile memory of the integrated circuit easily stealable. A physically unclonable function (PUF) provides a single device with a unique digital fingerprint that identifies it. The PUF only generates a digital fingerprint when a challenge input is received, and the key generated using the digital fingerprint is immediately destroyed after use. Therefore, the presence of a PUF prevents memory probing attacks from reading the stored key from memory, thereby ensuring the uniqueness and authenticity of the embedded device. However, existing research focuses on the protection of integrated circuit designs and neural network models based on PUFs. These methods are limited to specific devices and are not directly applicable to protecting digital copyrights.

[0004] The essence of digital watermarking technology for hiding information lies in modifying the redundant bits of the digital media in which the watermark is embedded, without causing perceptually noticeable changes. This modification contains the secret information to be hidden. However, existing watermarking technologies overlook the conflict between digital watermarking and copyright verification: 1. The key generated when embedding the digital watermark is inevitably leaked during the verification process, making it easy for malicious actors to erase the watermark; 2. Traditional digital watermarks take the form of pseudo-random sequences or binary images, which are easily forged and therefore unsuitable for identity verification. Some research has explored integrating biometrics into digital watermarks as copyright verification, but asserting copyright through biometrics may inadvertently disclose sensitive personal information and still does not address the issue of key leakage.

[0005] Blockchain technology offers a novel decentralized architecture for distributed applications. This technology has flourished alongside smart contracts, self-executing agreements that automatically fulfill conditions for all parties involved and streamline processes. The immutable nature of blockchain provides robust traceability for on-chain information. Blockchain-based digital rights management systems can be used to manage the digital copyrights of design works, but this approach requires users to submit their private keys to the application, which introduces the risk of centralization, where decryption programs could misappropriate the private keys. Similarly, Ma et al. proposed a scheme combining blockchain and watermarking to detect the misuse of online images. However, their approach did not adequately address identity fraud in copyright transfers, limiting the ability to accurately locate copyright infringers during tracking. Once data is leaked from the system, none of these works provide mechanisms to prevent unauthorized redistribution, necessitating the introduction of trusted hardware for protection. Summary of the Invention

[0006] To address the challenges of existing technologies, this paper proposes a copyright protection and traceability method that combines physically unclonable functions (PUFs) with blockchain technology. PUF devices register on the blockchain using their unique fingerprints. These devices then incorporate invisible watermarking technology to embed digital watermarks into the media. The watermark verification process is confined to the device, maintaining confidentiality during extraction, verifying identity during copyright exchange, and facilitating blockchain-based copyright transfer traceability.

[0007] The technical solution adopted by the present invention to solve the technical problem is: a copyright protection and traceability method based on a physical unclonable function watermark and blockchain, including:

[0008] PUF device registration steps: Build a PUF device and generate a device fingerprint through a challenge-response mechanism; the device fingerprint is registered on the blockchain and a public-private key pair is generated;

[0009] Copyright registration step: Use a certified PUF device to submit the hash summary of the digital media file to the blockchain to create a copyright identifier.

[0010] Furthermore, it also includes copyright transfer steps: the copyright owner negotiates transaction details with the purchaser and uses a smart contract to record transaction information; the copyright owner generates a copyright transfer identifier and signs it with a private key, and then converts the signature into a digital watermark and embeds it into the file; the copyright owner submits the watermark file and copyright transfer identifier to the blockchain and sends the watermark file to the purchaser; the purchaser uses the private key to decrypt the information, extracts the digital watermark after successful verification, uses the copyright owner's public key to verify the correctness of the watermark, and completes the payment through the blockchain; wherein, the copyright transfer identifier includes the ID of the copyright identifier recorded in the blockchain and the addresses of the two parties to the transaction.

[0011] Furthermore, the digital watermark embedding includes:

[0012] Use the elliptic curve digital signature algorithm to sign the copyright transfer mark and generate a digital watermark;

[0013] Generate an embedded position key using a PUF device;

[0014] The digital watermark is embedded into the digital medium according to an embedding position key, wherein the embedding position key includes a random number and a modification operation.

[0015] Furthermore, the digital watermark extraction includes:

[0016] Extract the embedded position key using a PUF device;

[0017] extracting a digital watermark from a digital medium based on an embedded position key;

[0018] The digital watermark signature is verified using the elliptic curve digital signature algorithm.

[0019] Furthermore, for copyright transfer, the copyright traceability and ownership verification can be achieved through the transaction information recorded in the blockchain and the watermark extraction process.

[0020] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects: the present invention provides a method for generating a unique key for an embedded device by means of the characteristics of a physical unclonable function, and then embeds a watermark based on a physical unclonable function for each digital media stored in the embedded device, thereby achieving the purpose of physical ownership of copyright. In order to solve the problem of privacy leakage in digital watermark extraction, a device that implements the properties of an unclonable function (PUF device) is used to implement a secure digital watermark extraction process to prevent the leakage of secrets in the copyright certification process. In order to ensure the traceability of copyright transfer, the PUF device is registered on the blockchain to ensure the authenticity of the information of both parties in the copyright transfer process, thereby preventing the problem of identity forgery and realizing traceability on the blockchain in combination with a secure digital watermark extraction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of a copyright protection and traceability method based on a physical unclonable function watermark and blockchain in an embodiment of the present invention;

[0022] Figure 2 This is the principle diagram of position key watermark technology;

[0023] Figure 3 Wiring diagram for the prototype system;

[0024] Figure 4 This is an information graphic about copyright transactions. Specific implementation plan

[0025] To facilitate understanding of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the present invention more thorough and comprehensive.

[0026] This paper proposes a copyright protection and traceability method based on physical unclonable function watermarks and blockchain. By leveraging the unclonable nature of trusted hardware security primitives and the traceability of blockchain, it achieves secure and traceable digital copyright management. In this paper, "copyright protection" is essentially a technical means of adding a physical device watermark to digital media, thereby binding it to the physical device. This technical means prevents copyright theft and tampering.

[0027] The process of this method is as follows Figure 1 As shown, it mainly includes the following steps: PUF device registration, copyright transfer process, digital watermark embedding and extraction, and blockchain traceability.

[0028] (1) PUF device registration

[0029] First, a PUF device is built in a secure environment. This secure environment ensures that the response to the challenge generated by the PUF device cannot be stolen or forged. After the PUF device is initialized, the manufacturer should select a random number c, which is then sent to the PUF device as a challenge. The PUF device builds a digital fingerprint DF and auxiliary data FE on SRAM, and uses the function Gen(DF,FE,c) to confuse the random number to produce the original output o c , and then use the hash function Hash(o c ) generates a response r, the PUF device sends the response to the manufacturer, who then replaces the device identifier id assigned to the device during manufacturing with the challenge-response pair<c,r> Stored in a secure database,<c,r> It is to verify the security fingerprint of the PUF device.

[0030] Next, the manufacturer selects a blockchain node as a certification authority, whose role is limited to the registration of the PUF device. It connects to the secure database for device authentication and then specifies the public parameters required to generate the public-private key pair, including the finite field F p Elliptic curve E on a,b :y 2 =x 3 +ax+b, where p is a large prime number, and a and b satisfy condition 4a 3 +27b 2 ≠0mod p,a,b∈F p . Then the certification body in F pChoose a large prime number n and its generator P∈E a,b , select a random number sk in n c As the private key, and calculate the public key pk c =sk c P. The certification authority stores the private key and publishes the public parameters and public key.

[0031] Finally, the PUF device needs to be registered on the blockchain. The PUF device selects a random number sk∈n as the device private key based on the public parameters and calculates the device public key pk=sk·P. The device uses the function Gen(DF,FE,sk) to confuse sk to produce the original output o sk The PUF device then sends an authentication request to the certification authority. Through key negotiation, the two parties jointly generate a temporary symmetric key for encrypting sensitive information. All subsequent communications are encrypted. The PUF device provides the certification authority with the device identifier id. The certification authority accesses the secure database to obtain the challenge random number c corresponding to the id and sends it to the PUF device. The PUF device uses Gen(DF, FE, c) to generate the original output o c , and then rely on the hash function Hash(o c ) Regenerate the response r and send it to the certification authority, which verifies<c,r> If the verification passes, the certification authority publishes a transaction on the chain to register the device as a certified device and stores the parameter pk. The hash value of pk is used as the address addr of the certified device on the blockchain. If the verification fails, the certification authority will send a notification to the device, requesting it to restart the registration process.

[0032] (2) Copyright transfer process

[0033] During the copyright transfer process, an authentication device is introduced as the holder of the digital copyright, and its fingerprint is embedded in the digital media. Copyright transfers only recognize authentication devices registered on the blockchain. Therefore, users participating in copyright transfers must possess the authentication device to ensure that their identities cannot be forged during the copyright transfer process. Copyright transfers involve two steps: copyright file registration and copyright file transaction.

[0034] A. Copyright File Registration

[0035] Digital media must be registered on the blockchain before it can be accepted as copyrighted. The only way to register digital media as copyrighted is for the authentication device to upload the file hash digest to the blockchain to generate a copyright identifier. A copyright identifier should contain: the file hash digest H(f) and the copyright owner's address addr. Suppose there is an external memory device storing a digital media f that requires copyright authentication. Authentication device A calculates the hash digest H(f) of f and packages H(f) and device A's address addr into the transaction TX.r The data is then sent to the blockchain. After verification, the blockchain's verification nodes verify the transaction and record it in a block. At this point, the original file remains on device A and has not been leaked.

[0036] B. Copyright File Transactions

[0037] 1. Initiate a transaction: Authentication device B wants to purchase document f from authentication device A. The two parties negotiate the transaction details, such as the price, the deadline for A to deliver the document, the deadline for B to pay, and the deadline for B to confirm receipt. These details are written into a smart contract and deployed on the blockchain.

[0038] 2. Payment: B deposits the negotiated price token into the smart contract, which notifies A to start the delivery process.

[0039] 3. Generate copyright transfer mark: A constructs a copyright transfer mark ctm AB , including the ID of the copyright identifier recorded in the blockchain and the addresses of both parties to the transaction. Then A embeds a digital watermark into the file f to obtain a new copyright file f′ and the embedding position key lk. Finally, A combines the hash summary H(f′) of f′ and ctm AB Assemble into transaction TX u The transaction is sent to the smart contract, which verifies the transaction and records it in the blockchain.

[0040] 4. File delivery: A encrypts lk using B’s public key, and then can send f′ and the encrypted lk ​​to B directly or indirectly.

[0041] 5. Verification and transfer: B uses the private key to decrypt the information and obtain f′ and lk. B first calculates the hash summary H(f′) of the file and compares it with the hash summary recorded in the blockchain. If they are not equal, B cancels the transaction; if they are equal, B extracts the digital watermark from f′ and then calculates ctm AB The hash of the digital watermark is used to verify the correctness of A's public key. Then, B sends a confirmation message to the smart contract, and the smart contract transfers the frozen tokens to A's address.

[0042] (3) Embedding and extraction of digital watermarks

[0043] The privacy risk of digital watermarks lies in the fact that extracting the watermark requires disclosing the key to the verifier. This means that a malicious verifier with access to the key can privately erase the watermark. Introducing a trusted third party as a verifier also introduces centralization risks. The PUF watermark proposed in this paper performs both the embedding and extraction processes on the authentication device.

[0044] A. Digital watermark embedding

[0045] Using the ECDSA algorithm, the private key pair ctm stored by the authentication device A is used. AB Signature, then convert the signature into binary bit form to generate a digital watermark w with physical ownership AB Then, based on the least significant bit watermark embedding algorithm, a watermark embedding and extraction algorithm that relies on the embedding position key is designed, such as Figure 2 As shown in the figure, the principle is that the low bits of the bits of information stored in digital media are randomly distributed, with 0 and 1 accounting for half each. Therefore, the combination of the second lowest bits can be used as the condition for modifying the lowest bit. For example, for a 24-bit true color image, a pixel p ij The corresponding RGB format is R = {r0, r1, ..., r7}, G = {g0, g1, ..., g7}, B = {b0, b1, ..., b7}, and the second lowest bit information group {r6, g6, b6} can be extracted. Then, a random number generator is used to generate a random number x of appropriate length and perform bitwise XOR operation with the information group to obtain the feature group. Then, based on the amount of information to be embedded and the defined rules, the feature groups are classified and the modification actions for the lowest bit are defined. Taking the image format as an example, for any pixel in the image format, four modification actions are defined:

[0046] 1. Lowest bit replacement (LSBR): For a pixel p in RGB format ij One color channel rgb ij and a bit m of the ciphertext m b , replace the next bit of the ciphertext with the lowest bit.

[0047]

[0048] 2. Lowest bit match (LSBM): pixel p in RGB format ij-1 The lowest bit of the pixel is filled with a random number. ij One color channel rgb ij and a bit m of the ciphertext m b , match the next bit of the ciphertext to the lowest bit.

[0049]

[0050] Where rand is 1 or -1.

[0051] 3. Random number filling: For RGB format pixel p ij The lowest bit of the color channel rgb ij Fill with random numbers.

[0052] 4. Unchanged: RGB format pixel p ij The lowest bit remains unchanged.

[0053] lk is constructed through x and modification actions, where the modification actions can be independently defined according to the file format to improve security.

[0054] B. Digital Watermark Extraction

[0055] Authentication device B uses its own device private key to decrypt lk, and processes the file according to x in lk and the defined modification action to obtain the digital watermark w AB , and then verify the digital watermark w according to the transaction records on the chain AB In this process, malicious verifiers do not have relevant information about lk and therefore cannot remove the watermark without destroying the file, thus ensuring the effectiveness of copyright protection.

[0056] (4) Blockchain traceability

[0057] During the copyright transfer process, the authentication device records transaction information on the blockchain, ensuring that each copyright transfer has a traceable record. Specifically, authentication device C requests the purchase of file f′ from authentication device B. The two parties complete the file transaction according to the steps defined in the copyright transfer process. B sends the copyright file f″ containing the watermark and the location key lk′ to C and records the copyright transfer identifier ctm on the blockchain. BC In this process, only when the hash digest matches ctm AB Only when B encrypts f′, C then uses the key lk′ to extract the watermark and verify it, thus confirming that the copyright transfer path is Realize the traceability of copyright transfer.

[0058] To verify the feasibility of this invention, a prototype system was developed. This prototype system uses the NXP Semiconductors LPC55S69-EVK development board, equipped with a dual-core Arm Cortex-M33 microcontroller, and uses SRAM PUF to establish a root of trust. The blockchain part uses go-ethereum, an Ethereum protocol implemented in Golang, to build a private blockchain network. The system connection and configuration are as follows: Figure 3 shown.

[0059] The authentication server stores the physical unclonable information of the two development boards. After establishing a secure connection with the server, the development board proves its identity to the authentication server by submitting a correct response, and then registers the public key address in the blockchain. Then, a Lena image in BMP format is used as an experimental example. In the seller's development board, the image is registered in the blockchain. The copyright is as follows Figure 4As shown in (a) above, the seller and buyer then reach an agreement on the copyrighted file, with the buyer publishing a smart contract on the blockchain. On the development board, the seller constructs a copyright transfer identifier and signs it using the device's private key. This content is then embedded into an image to generate a watermarked Lena image, with a peak signal-to-noise ratio of 55.387 dB.

[0060] Then calculate the hash value of the embedded watermark image, construct a transaction and upload it to the blockchain. The transaction content is as follows: Figure 4 As shown in (b) above, after the buyer obtains the file, the development board decrypts the position key and then verifies the watermark signature. Throughout this process, the position key remains intact, preventing the buyer from obtaining the original image by erasing the watermark.

[0061] The present invention also considers an attack method, namely the malicious selling behavior of the seller, such as repeatedly selling copyrighted files that have been registered on the chain. After the development board detects the existence of copyrighted files with the same hash, it will refuse to register them; or the seller registers on the chain by modifying the file hash and completes the transaction process. If other users find similar content on the chain, they can determine the original ownership of the file through the timestamp and traceability of the on-chain transaction, and ban the development board by reporting it to the blockchain to avoid it from suffering economic losses.

Claims

1. A copyright protection and traceability method based on physical unclonable function watermark and blockchain, characterized by: include: PUF device registration steps: Build a PUF device and generate a device fingerprint through a challenge-response mechanism; The device fingerprint is registered on the blockchain and a public-private key pair is generated; Copyright registration step: Use a certified PUF device to submit the hash summary of the digital media file to the blockchain to create a copyright identifier; The copyright transfer process includes the following steps: the copyright owner negotiates the transaction details with the buyer and uses a smart contract to record the transaction information; the copyright owner generates a copyright transfer identifier and signs it with a private key, then converts the signature into a digital watermark and embeds it into the file; the copyright owner submits the watermark file and copyright transfer identifier to the blockchain and sends the watermark file to the buyer; the buyer uses the private key to decrypt the information, extracts the digital watermark after successful verification, verifies the correctness of the watermark with the copyright owner's public key, and completes the payment through the blockchain; the copyright transfer identifier includes the copyright identifier recorded in the blockchain and the addresses of the two parties to the transaction.

2. The copyright protection and traceability method based on physical unclonable function watermark and blockchain according to claim 1 is characterized in that: The digital watermark embedding includes: Use the elliptic curve digital signature algorithm to sign the copyright transfer mark and generate a digital watermark; Generate an embedded position key using a PUF device; The digital watermark is embedded into the digital medium according to an embedding position key, wherein the embedding position key includes a random number and a modification operation.

3. The copyright protection and traceability method based on physical unclonable function watermark and blockchain according to claim 1 is characterized in that: The extracting of digital watermark comprises: Extract the embedded position key using a PUF device; extracting a digital watermark from a digital medium based on an embedded position key; The digital watermark signature is verified using the elliptic curve digital signature algorithm.

4. The copyright protection and traceability method based on physical unclonable function watermark and blockchain according to claim 1 is characterized in that: For copyright transfer, the copyright traceability and ownership verification are achieved through the transaction information recorded in the blockchain and the watermark extraction process.

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