Time-limited NFT permission protection method based on time interval signature

Abstract

The invention provides a time-limited NFT permission protection method based on a time interval signature, and belongs to the technical field of block chains. Firstly, the invention provides a time interval signature scheme, the signature uses a product zero-knowledge proof protocol as a constituent part of a signature structure, and on the basis of a TIS, a time-limited NFT permission protection method is provided and mainly comprises the following execution steps: 1, initializing a system; 2, asset storage; 3, generating NFT (Non-Fourier Transform); 4, transferring the use right of the NFT; 5, activating the transaction; and 6, the NFT right to use expires. According to the authority protection method, on the basis of a flexible timing signature scheme-time interval signature, authorization and revocation time of the NFT use right is supported to be preset, the NFT use right is flexibly managed through timing control, and timing transfer and automatic restoration of the NFT use right are promoted.

Description

Technical Field

[0001] The present invention relates to a time-limited NFT rights protection method based on time interval signature, which belongs to the technical field of blockchain. Background Art

[0002] Timed cryptography is a very important and promising field in cryptography research, providing innovative solutions for various practical applications. By integrating time constraints, timed cryptography extends the functionality of traditional cryptographic schemes and introduces new time-security properties to cryptographic primitives, improving the security and application flexibility of cryptographic primitives. A large number of timed cryptographic schemes have emerged, including time-lock puzzles (TLPs), verifiable delay functions (VDFs), timed-release encryption (TRE), and timed commitments (TCs). These schemes not only enrich the research field of cryptography, but also open up new possibilities for the application of cryptography.

[0003] Deferred Verifiable Functions (VDFs). In 1996, Rivest et al. introduced the first timed cryptographic primitive, called the RSW time-lock puzzle, for constructing the TRE scheme. The scheme ensures that encrypted data can only be decrypted after a predetermined time, even by an adversary with significant parallel computing power. In 2018, Boneh et al. introduced the concept and formal definition of a VDF, which requires a specified time to compute a unique output that can be quickly verified. De Feo et al. proposed a VDF construction based on elliptic curves and bilinear pairings, but this construction only allows a fixed time difficulty to be set at initialization. Subsequently, Pietrzak and Wesolowski proposed DVDF constructions based on the repeated square assumption and the Fia-Shamir (FS) heuristic, respectively. Attias et al. analyzed these two VDF constructions and showed that while Pietrzak's scheme provides better performance, the result is a larger proof. In contrast, Wesolowski's scheme generates smaller proofs but takes longer to verify. Ephraim et al. proposed a continuous VDF scheme based on the repeated square assumption and a variant of the FS heuristic for constant integer proofs.

[0004] Timed Signatures (TS). Thyagarajan et al. introduced the concept of Verifiable Timed Signatures (VTS) and gave specific constructions of BLS, Schnorr, and ECDSA signatures. In these schemes, the signer submits a signature within a period of time, during which anyone can verify whether the signature contains a valid signature. They also used VTS to implement an unlinkable payment channel network on the blockchain. However, the signature size and computational cost grow linearly with the number of signature shares. Zhou et al. proposed Verifiable Timed Adapter Signatures, a new cryptographic primitive that can reduce the computational complexity of VTS from linear to constant levels. Thyagarajan et al. developed Verifiable Timed Linkable Ring Signatures (VTLRS), which can hide linkable ring signatures within a predetermined time. VTLRS is then used to build a privacy-preserving payment channel protocol for the cryptocurrency Monero. Bao et al. proposed a verifiable timed RSA signature scheme based on trapdoor VDF and RSA signatures, which maintains a constant-size signature. Arun et al. developed a short-term signature scheme based on VDF, which introduces time constraints to ensure that the signature expires naturally after a predetermined time. It reduces the risk of misusing outdated information and databases.

[0005] The protection of rights in NFT digital asset transactions has always been an important issue faced by the blockchain. Currently, two types of timed signatures have been developed. The first is called a verifiable timed signature (VTS), which implements a delay before the signature takes effect; the second type is a short-lived signature (SLS), which allows the expiration time of the signature to be set when the signature is created. The above two signature schemes can guarantee the smooth transfer and recovery of usage rights during NFT transactions to a certain extent. However, some application scenarios that require time-sensitive authorization require the setting of activation time and expiration time, and the existing timed signature schemes cannot meet this requirement. Therefore, the present invention proposes a time-limited NFT rights protection method based on time interval signatures. The time interval signature (TIS) scheme adopted by the present invention can flexibly set the effective time and expiration time of the signature, making the NFT digital asset rights division more flexible and secure. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the existing timed signature scheme causes the NFT usage rights to be unable to be flexibly and securely divided according to the wishes of the creator and the buyer, that is, the permission transfer and automatic restoration of NFT lack the guarantee of a suitable timed signature scheme, and proposes a time-limited NFT permission protection method based on time interval signature.

[0007] The objectives of the present invention are achieved through the following technical solutions.

[0008] First, the present invention proposes a time interval signature (TIS) scheme, which can flexibly set the validity time and expiration time of the signature. The signature uses a zero-knowledge proof of product (Zero-Knowledge Proof of Product, ZKPoP) protocol as a component of the signature structure. Based on TIS, a time-limited NFT rights protection method is proposed, named TimeGuardian, which flexibly manages NFT usage rights through timing control and promotes the timing transfer and automatic restoration of NFT usage rights.

[0009] 1. The product zero-knowledge proof (ZKPoP) protocol mainly includes the following three algorithms:

[0010] (1)ZK.Setup(1 λ )→pp: When a security parameter λ is input, the algorithm outputs a public parameter pp as the public input of other algorithms.

[0011] (2) ZK.Prove(α, ω) → π: Given a statement α and a witness ω, the algorithm outputs a proof π.

[0012] (3) ZK.Verify(α, π) → {1, 0}: Given a statement α and a proof π, the algorithm outputs 1 if π is valid, otherwise it outputs 0.

[0013] 2. The Time Interval Signature (TIS) scheme mainly includes the following six algorithms:

[0014] (1)TIS.KGen(1 λ )→(pk, sk): When a security parameter λ is input, the key generation algorithm outputs a public key pk and a private key sk.

[0015] (2)TIS.Sign(pk, sk, t 1 , t 2 , m, b)→(C, π 1 ): Enter a public key pk, a private key sk, and an activation time t 1 , an expiration time t2 , a message m and a beacon b, the signature algorithm outputs a commitment C of the signature for (m, b) and a proof π 1 .

[0016] (3)TIS.Verify(pk, C, π 1 , m, b) → {0, 1}: Input a public key pk, a commitment C, and a proof π 1 , a message m and a beacon b, the verification algorithm outputs 1 if the signature of (m, b) embedded in C is valid, otherwise it outputs 0.

[0017] (4)TIS.Open(pk, sk, C, m, b)→(σ, y): When inputting a public key pk, a private key sk, a commitment C, a message m and a beacon b, the open algorithm outputs a committed short-term valid signature tuple σ and a result y.

[0018] (5)TIS.OpenVer(pk, C, σ, y, m, b) → {0, 1}: Given a public key pk, a commitment C, a short-lived signature tuple σ, a result y, a message m, and a beacon b, the verification algorithm outputs 1 if the signature of (σ, y) embedded in C is valid, otherwise it outputs 0.

[0019] (6)TIS.ForceOp(pk, C, m, b)→(σ, y): Given a public key pk, a commitment C, a message m and a beacon b, the forgery open algorithm outputs a committed short-term valid signature tuple σ and a result y.

[0020] 3. Time-limited NFT permission protection method (TimeGuardian)

[0021] The system model of this permission includes 5 entities: creator, buyer, NFT market,

[0022] IPFS and blockchain.

[0023] Creator: A creator is an individual who owns a digital asset. These creators are responsible for the initial creation, uploading, and minting of digital asset NFTs. By generating a TIS-based transaction for the transfer of NFT usage rights, the asset creator grants the buyer the right to use the asset.

[0024] Buyer: A buyer is an individual who purchases the right to use virtual currency within a certain period of time.

[0025] NFT Market: NFT Market is a digital trading platform dedicated to displaying and selling NFTs. Buyers can easily browse and purchase NFTs on the market.

[0026] IPFS: IPFS is a distributed, peer-to-peer, permissionless file system for storing digital assets and their metadata.

[0027] Blockchain: Blockchain is a decentralized ledger that records all transactions and the execution of smart contracts. In the blockchain, participants in the blockchain are responsible for verifying transactions, and blocks serve as beacons for TIS.

[0028] The threat model for this permission includes two types of malicious behavior: illegal transfer and transaction rejection.

[0029] Illegal transfer: adversary (i.e. malicious creators) attempt to illegally transfer the right to use NFTs by forging TIS transactions.

[0030] Transaction Rejection: Adversary Failure to disclose the short-term signature in the TIS hinders the execution of the NFT usage transfer transaction. This behavior prevents the buyer from obtaining the right to use the NFT even though the buyer has paid. The design goals of this right include three outcomes: time controllability, enforceability, and automatic expiration.

[0031] Time controllability: To solve the problem of illegal transfer, the creator can accurately define the buyer’s NFT usage period, from t 1 to 2 , effectively preventing transaction forgery.

[0032] Enforceability: To address the issue of transaction rejection, buyers are allowed to compulsorily disclose TIS, thereby guaranteeing the transfer of NFT usage rights.

[0033] Automatic expiration: The right to use the NFT automatically expires after a set period of time, ensuring the timely recovery of the right to use the NFT.

[0034] The present invention proposes a time-limited NFT rights protection method based on time interval signature, and the main execution steps are as follows: 1. System initialization. 2. Asset storage. 3. NFT generation. 4. NFT usage rights transfer. 5. Transaction activation. 6. NFT usage rights expiration. The present invention uses the TIS signature scheme to sign NFT usage rights transactions, clearly defines the activation and expiration time of these rights, and each NFT is associated with a unique global identifier tokenID, as follows:

[0035] 1. System initialization: Each user uses TIS.KGen(1 λ ) Generate a public-private key pair (pk, sk). Then, add a blockchain address for each user.

[0036] 2. Asset storage: This step consists of two sub-stages.

[0037] Upload assets: Upload digital assets (da), such as artwork images, video files, ENS domain names, or CryptoKitties, and IPFS returns a unique immutable address daUrl = H (da).

[0038] Metadata upload: Create a JSON file to store the metadata of the digital asset, including name, description, digital asset file address daUrl, author and copyright information. In addition, it stipulates that the purchased NFT usage rights are only for a certain period of time, after which the copyright and usage rights are automatically restored to the creator. This JSON file is then uploaded to IPFS, which returns a unique immutable address metaDataUrl = H (metadata)

[0039] 3. NFT generation: This step consists of two sub-stages.

[0040] NFT minting: The creator calls mint (add c , tokenId, metaDataUrl) to mint NFT. This process assigns ownership of the NFT tokenId to the creator's address add c , and record the relevant metadata link metaDataUrl.

[0041] NFT Listing: Once the blockchain network accepts the NFT transaction, it is permanently recorded on the blockchain and assigned a unique identifier tokenId and related metadata. The creator then lists their NFT on markets such as OpenSea or Rariable and sets a price.

[0042] 4. Transfer of NFT usage rights: This step includes two sub-stages.

[0043] NFT Sales: Buyers browse the marketplace, select the NFT they want, and purchase the rights to use it for a period of time.

[0044] ·Transaction creation: After the buyer completes the payment, the creator uses the transferFrom (add c , add b , tokenId) transfers the right to use the NFT to the buyer's address add b , thereby generating NFT usage rights transfer transaction tx fr From. Transaction tx fr From using TIS.Sign(pk, sk, t 1 , t 2 , tx frFrom, b) → (C, π 1 ) signature. Here, the beacon b = H (header), where header represents the latest block header. Specifically, transaction tx fr From through TIS (C, π 1 ) specifies the effective time t 1 and expiration time t 2 If tx fr From needs to take effect immediately, then t 1 Set to 0.

[0045] 5. Transaction Activation: This step consists of two sub-stages.

[0046] Transaction verification: Blockchain participants can use TIS.Verify(pk, C, π) on VTSLS 1 , tx fr From, H (header)) verify transaction tx fr From TIS(C,π 1 ). In addition, if the received transaction time exceeds t 2 +t, then transaction tx fr From is invalid, where t is the timestamp corresponding to the random beacon b=H(header).

[0047] Signature disclosure: If the creator 1 After that, without actively disclosing the short-lived signature tuple σ embedded in C, the buyer can execute TIS.ForceOp(pk, C, tx fr From, H (header)) is forced to be disclosed, thereby activating the transaction tx fr From. Then, broadcast tx to the blockchain network fr From. The buyer can use the smart contract’s tokenURI (tokenId) to obtain a metadata link that allows access to the purchased digital assets.

[0048] 6. NFT usage rights expire: This step includes two sub-stages.

[0049] Transaction verification: Participants use a short-term signature verification algorithm to verify the transaction tx fr From's short-lived signature tuple σ.

[0050] Signature expires: at time t 2 After that, anyone can use the short-term signature forging algorithm to forge the short-term signature tuple σ. This means that the signature tuple σ is not valid for tx fr From has expired, thus allowing the seller to reclaim the right to use the NFT from the buyer.

[0051] Beneficial Effects

[0052] 1. This invention proposes a time-limited NFT rights protection method called TimeGuardian. This method is based on a flexible timing signature scheme, Time Interval Signature (TIS), supports pre-setting the authorization and revocation time of NFT usage rights, flexibly manages NFT usage rights through timing control, and promotes the timing transfer and automatic restoration of NFT usage rights.

[0053] 2. The TIS signature scheme proposed in the present invention can flexibly set the effective time and expiration time, and set the effective time of the signature within the minimum time period that meets the requirements, which can effectively prevent the leakage and cracking of the signature outside the effective time, and enhance the protection ability of the signature. At the same time, compared with the existing verifiable timed signature schemes VT-BLS, VT-Schnorr, VT-ECDSA, and VT-RSA, the signature size of the TIS signature scheme is reduced by 98.68%, 98.67%, 98.67%, and 57.14%, respectively, which reduces the bandwidth pressure of communication on the blockchain and has higher signature efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Transaction verification and signature expiration graph;

[0055] Figure 2 Timing signature comparison chart. DETAILED DESCRIPTION

[0056] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0057] Example

[0058] First, the present invention proposes a time interval signature (TIS) scheme, which can flexibly set the validity time and expiration time of the signature. The signature uses a zero-knowledge proof of product (Zero-Knowledge Proof of Product, ZKPoP) protocol as a component of the signature structure. Finally, based on TIS, a time-limited NFT rights protection method is proposed, named TimeGuardian, which flexibly manages NFT usage rights through timing control and promotes the timing transfer and automatic restoration of NFT usage rights.

[0059] 1. The product zero-knowledge proof (ZKPoP) protocol mainly includes the following three algorithms:

[0060] (1)ZK.Setup(1 λ)→pp: When a security parameter λ is input, the algorithm outputs a public parameter pp as the public input of other algorithms.

[0061] (2) ZK.Prove(α, ω) → π: Given a statement α and a witness ω, the algorithm outputs a proof π.

[0062] (3) ZK.Verify(α, π) → {1, 0}: Given a statement α and a proof π, the algorithm outputs 1 if π is valid, otherwise it outputs 0.

[0063] 2. The time interval signature (TIS) scheme mainly includes the following 6 algorithms:

[0064] (1)TIS.KGen(1 λ )→(pk, sk): When a security parameter λ is input, the key generation algorithm outputs a public key pk and a private key sk.

[0065] (2)TIS.Sign(pk, sk, t 1 , t 2 , m, b)→(C, π 1 ): Enter a public key pk, a private key sk, and an activation time t 1 , an expiration time t 2 , a message m and a beacon b, the signature algorithm outputs a commitment C of the signature for (m, b) and a proof π 1 .

[0066] (3)TIS.Verify(pk, C, π 1 , m, b) → {0, 1}: Input a public key pk, a commitment C, and a proof π 1 , a message m and a beacon b, the verification algorithm outputs 1 if the signature of (m, b) embedded in C is valid, otherwise it outputs 0.

[0067] (4)TIS.Open(pk, sk, C, m, b)→(σ, y): When inputting a public key pk, a private key sk, a commitment C, a message m and a beacon b, the open algorithm outputs a committed short-term valid signature tuple σ and a result y.

[0068] (5)TIS.OpenVer(pk, C, σ, y, m, b) → {0, 1}: Given a public key pk, a commitment C, a short-lived signature tuple σ, a result y, a message m, and a beacon b, the verification algorithm outputs 1 if the signature of (σ, y) embedded in C is valid, otherwise it outputs 0.

[0069] (6)TIS.ForceOp(pk, C, m, b)→(σ, y): Given a public key pk, a commitment C, a message m and a beacon b, the forgery open algorithm outputs a committed short-term valid signature tuple σ and a result y.

[0070] 3. Time-limited NFT permission protection method (TimeGuardian)

[0071] The system model of this permission includes 5 entities: creator, buyer, NFT market,

[0072] IPFS and blockchain.

[0073] Creator: A creator is an individual who owns a digital asset. These creators are responsible for the initial creation, uploading, and minting of digital asset NFTs. By generating a TIS-based transaction for the transfer of NFT usage rights, the asset creator grants the buyer the right to use the asset.

[0074] Buyer: A buyer is an individual who purchases the right to use virtual currency within a certain period of time.

[0075] NFT Market: NFT Market is a digital trading platform dedicated to displaying and selling NFTs. Buyers can easily browse and purchase NFTs on the market.

[0076] IPFS: IPFS is a distributed, peer-to-peer, permissionless file system for storing digital assets and their metadata.

[0077] Blockchain: Blockchain is a decentralized ledger that records all transactions and the execution of smart contracts. In the blockchain, participants in the blockchain are responsible for verifying transactions, and blocks serve as beacons for TIS.

[0078] The threat model for this permission includes two types of malicious behavior: illegal transfer and transaction rejection.

[0079] Illegal transfer: adversary (i.e. malicious creators) attempt to illegally transfer the right to use NFTs by forging TIS transactions.

[0080] Transaction Rejection: Adversary Failure to disclose the short-term signature in the TIS hindered the execution of the NFT usage rights transfer transaction. This behavior prevented the buyer from obtaining the right to use the NFT even though the buyer had already paid.

[0081] The design goals of this permission include three outcomes: time controllability, enforceability, and automatic expiration.

[0082] Time controllability: To solve the problem of illegal transfer, the creator can accurately define the buyer’s NFT usage period, from t 1 to 2 , effectively preventing transaction forgery.

[0083] Enforceability: To address the issue of transaction rejection, buyers are allowed to compulsorily disclose TIS, thereby guaranteeing the transfer of NFT usage rights.

[0084] Automatic expiration: The right to use the NFT automatically expires after a set period of time.

[0085] Ensures timely recovery of NFT usage rights.

[0086] Figure 1 The entity interaction relationship and method execution steps of the limited-time NFT rights protection method. Consistent with the technical solution process protected by the invention content, the creator first uploads the created digital assets and metadata to IPFS, then mints the NFT, and sends the NFT list to the NFT market for buyers to choose. The buyer selects the desired NFT and purchases the right to use the NFT for a specified time. The creator then uses VTSLS to generate the NFT transfer transaction selected by the buyer, writes it into the smart contract, and deploys it to the blockchain. The buyer opens VTSLS to upload the NFT transfer transaction to the chain, uses the latest block as the transaction beacon, triggers the smart contract to complete the transaction, and enables the buyer to have the right to use the NFT for that time period until the signature expires.

[0087] Figure 2 This is a visual illustration of the two existing timing signature schemes and the TIS scheme proposed in the present invention. 1 After the forward timing signature takes effect at time t 2 After the expiration, these two signatures can only be effective around a certain time point. The TIS solution proposed in the present invention is effective at time t 1 and time t 2 It has more flexible and secure application potential. In the distribution of digital content, such as video, music or software, content owners can use TIS solutions to limit access or usage periods to ensure that digital content can only be accessed within authorized time intervals. In contracts and agreements, TIS solutions can be used to ensure that legal and commercial contracts automatically take effect or expire at a predetermined time. In scenarios where temporary access control or permission allocation is required, such as employee access to sensitive data or systems, the solution can ensure that permissions automatically expire after a specified time. In voting protocols, such as voting systems during elections, TIS solutions can ensure that ballots are only valid during the election and automatically expire after the election.

[0088] The present invention proposes a time-limited NFT permission protection method based on time interval signature. The method is based on a flexible timing signature scheme, namely time interval signature (TIS), supports pre-setting of authorization and revocation time of NFT usage rights, flexibly manages NFT usage rights through timing control, promotes the timing transfer and automatic restoration of NFT usage rights, and makes the division of NFT digital asset rights more flexible and secure.

Claims

1. A time-limited NFT rights protection method based on time interval signature, characterized in that: The main execution steps are as follows:

1. System initialization; 2. Asset storage; 3. NFT generation; 4. NFT usage rights transfer; 5. Transaction activation; 6. NFT usage rights expiration. The present invention uses a time interval signature scheme to sign NFT usage rights transactions, clearly defines the activation and expiration times of these rights, and each NFT is associated with a unique global identifier tokenID.

2. A time-limited NFT rights protection method based on time interval signature as described in claim 1, characterized in that: First, the present invention proposes a time interval signature (TIS) scheme, which can flexibly set the validity time and expiration time of the signature. The signature uses a zero-knowledge proof of product (ZKPoP) protocol as a component of the signature structure. Finally, based on TIS, a time-limited NFT rights protection method is proposed, named TimeGuardian, which flexibly manages the NFT usage rights through timing control and promotes the timing transfer and automatic restoration of NFT usage rights. The product zero-knowledge proof ZKPoP protocol mainly includes the following three algorithms: (1)ZK.Setup(1 λ )→pp: When a security parameter λ is input, the algorithm outputs a public parameter pp as the public input of other algorithms; (2) ZK.Prove(α, ω) → π: Given a statement α and a witness ω, the algorithm outputs a proof π. (3) ZK.Verify(α, π) → {1, 0}: Given a statement α and a proof π, the algorithm outputs 1 if π is valid, otherwise it outputs 0. The time interval signature TIS scheme mainly includes the following 6 algorithms: (1)TIS.KGen(1 λ )→(pk, sk): When a security parameter λ is input, the key generation algorithm outputs a public key pk and a private key sk; (2) TIS.Sign(pk, sk, t1, t2, m, b) → (C, π1): When a public key pk, a private key sk, an activation time t1, an expiration time t2, a message m and a beacon b are input, the signature algorithm outputs a commitment C and a proof π1 of the signature for (m, b); (3) TIS.Verify(pk, C, π1, m, b) → {0, 1}: When a public key pk, a commitment C, a proof π1, a message m and a beacon b are input, the verification algorithm outputs 1 if the signature of (m, b) is embedded in C and is valid, otherwise it outputs 0; (4) TIS.Open(pk, sk, C, m, b) → (σ, y): Given a public key pk, a private key sk, a commitment C, a message m, and a beacon b, the open algorithm outputs a committed short-term valid signature tuple σ and a result y; (5) TIS.OpenVer(pk, C, σ, y, m, b) → {0, 1}: When a public key pk, a commitment C, a short-term valid signature tuple σ, a result y, a message m and a beacon b are input, the verification algorithm outputs 1 when the signature of (σ, y) is embedded in C and is valid, otherwise it outputs 0; (6) TIS.ForceOp(pk, C, m, b) → (σ, y): When a public key pk, a commitment C, a message m and a beacon b are input, the forgery open algorithm outputs a committed short-term valid signature tuple σ and a result y; The time-limited NFT rights protection method (TimeGuardian) The system model of this permission includes 5 entities: creator, buyer, NFT market, IPFS and blockchain, as follows: Creator: A creator is an individual who owns digital assets. These creators are responsible for the initial creation, uploading, and minting of digital asset NFTs. By generating TIS-based transactions for the transfer of NFT usage rights, asset creators grant buyers the right to use the assets; Buyer: A buyer is an individual who purchases the right to use virtual currency within a certain period of time; NFT Marketplace: NFT Marketplace is a digital trading platform dedicated to displaying and selling NFTs, where buyers can easily browse and purchase NFTs on the market; IPFS: IPFS is a distributed, peer-to-peer, permissionless file system for storing digital assets and their metadata. Blockchain: Blockchain is a decentralized ledger that records all transactions and the execution of smart contracts. In the blockchain, participants in the blockchain are responsible for verifying transactions, and blocks serve as beacons for TIS; The threat model for this permission includes two malicious behaviors: illegal transfer and transaction rejection Illegal transfer: adversary (i.e. malicious creators) attempt to illegally transfer the right to use NFTs through forged TIS transactions; Transaction Rejection: Adversary Failure to disclose the short-lived signature in the TIS, thereby hindering the execution of the NFT usage rights transfer transaction, which prevents the buyer from obtaining the right to use the NFT even though the buyer has paid; The design goals of this permission include three outcomes: time controllability, enforceability, and automatic expiration. Time controllability: In order to solve the problem of illegal transfer, the creator can accurately define the buyer's NFT usage period, from t1 to t2, effectively preventing transaction forgery; Enforceability: To address the issue of transaction rejection, buyers are allowed to compulsorily disclose TIS, thereby guaranteeing the transfer of NFT usage rights; Automatic expiration: The right to use the NFT automatically expires after a set period of time, ensuring the timely recovery of the right to use the NFT.

3. A time-limited NFT rights protection method based on time interval signature as described in claim 1 or 2, characterized in that: The time-limited NFT rights protection method is as follows:

1. System initialization: Each user uses TIS.KGen(1 λ ) Generate a public-private key pair (pk, sk), and then add a blockchain address for each user; 2. Asset storage: This step includes two sub-stages Upload assets: Upload digital assets (da), such as artwork images, video files, ENS domain names or CryptoKitties, etc. IPFS returns a unique immutable address daUrl = H (da); Metadata upload: Create a JSON file to store the metadata of the digital asset, including name, description, digital asset file address daUrl, author and copyright information. In addition, it stipulates that the purchased NFT usage rights are only for a certain period of time, after which the copyright and usage rights are automatically restored to the creator. This JSON file is then uploaded to IPFS, which returns a unique immutable address metaDataUrl = H (metadata); 3. NFT generation: This step includes two sub-stages NFT minting: The creator calls mint (add c , tokenId, metaDataUrl) to mint NFT, this process assigns the ownership of NFT tokenId to the creator's address add c , and record the relevant metadata link metaDataUrl; NFT Listing: Once the blockchain network accepts the NFT transaction, it is permanently recorded on the blockchain and assigned a unique identifier tokenId and related metadata. The creator then lists their NFT on a marketplace such as OpenSea or Rariable and sets a price.

4. Transfer of NFT usage rights: This step includes two sub-stages NFT Sales: Buyers browse the marketplace, select the NFT they want, and purchase the right to use it for a period of time; ·Transaction creation: After the buyer completes the payment, the creator uses the transferFrom (add c , add b , tokenId) transfers the right to use the NFT to the buyer's address add b , thereby generating NFT usage rights transfer transaction tx fr From, transaction tx fr From uses TIS.Sign(pk, sk, t1, t2, tx fr From,b)→(C,π1) signature, where the beacon b=H(header), where header represents the latest block header, specifically, transaction tx fr From specifies the validity time t1 and expiration time t2 through TIS(C,π1). If tx fr If From needs to take effect immediately, t1 is set to 0; 5. Transaction Activation: This step consists of two sub-stages Transaction verification: Blockchain participants can use TIS.Verify(pk, C, π1, tx fr From,H(header)) verify transaction tx fr From's TIS(C,π1), in addition, if the received transaction time exceeds t2+t, then transaction tx fr From is invalid, where t is the timestamp corresponding to the random beacon b=H(header); Signature disclosure: If the creator does not proactively disclose the short-lived signature tuple σ embedded in C after time t1, the buyer can execute TIS.ForceOp(pk, C, tx fr From,H(header)) is forced to be disclosed, thereby activating the transaction tx fr From, then, broadcasts tx to the blockchain network fr From, the buyer can use the smart contract’s tokenURI (tokenId) to obtain a metadata link that allows access to the purchased digital assets; 6. NFT usage rights expire: This step includes two sub-stages Transaction verification: Participants use a short-term signature verification algorithm to verify the transaction tx fr From's short-lived signature tuple σ; Signature expiration: After time t2, anyone can use the short-term signature forgery algorithm to forge a short-term signature tuple σ, which means that the signature tuple σ is not valid for tx fr From has expired, thus allowing the seller to reclaim the right to use the NFT from the buyer.

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