# A Non-Fungible Token and Blockchain-Based Cotton Lint Traceability Solution
## 3 Proposed Solution
### System Components  
Figure 1 presents the architecture of the traceability system designed for the cotton lint supply chain, which consists of five core components: participants, a decentralised application (DApp), an off-chain storage system, a blockchain platform and smart contracts. DApps allow stakeholders to interact with various system parts, including smart contracts, distributed storage and various on-chain resources. The smart contracts deployed on the blockchain empower stakeholders to interact with the blockchain ledger transparently.  
* Participants: In the proposed solution, the core participants include cotton-growing farms, producers, warehouse companies, the Market Supervision and Administration Bureau (MSAB) and textile companies, as well as the final customer. It is important to note that only authorised and qualified participants can initiate the NFT creation process. Any quality issues with the participant's products can be quickly traced back  
Figure 1: Proposed blockchain and NFT-based traceability architecture for cotton supply chain.  
to the source through the traceability information associated with the NFT [28]. This mechanism ensures supply chain transparency and effective accountability.
* Ether blockchain: The Ether blockchain, a second-generation decentralised platform, supports users in executing custom code and operations in a distributed environment. Compared to Bitcoin, the Ether network not only has its cryptocurrency, Ether, but it can also interact with Externally Owned Accounts (EOA) and Contract Accounts (CA) [29]. In this case, the EOA is directly controlled by the entity holding the private key, while the smart contract code governs the CA. In the constructed system, the NFT in the cotton lint supply chain and all the related transaction information are permanently and securely recorded on the Ethereum blockchain, thus ensuring the security and transparency of the supply chain data.
* Smart contract (SC): Smart contracts are self-executing protocols running on the blockchain whose terms are defined and enforced by code, ensuring the comparability and integrity of contract execution. We enable stakeholders to interact transparently with the blockchain ledger by deploying smart contracts. Smart contracts designed using the ERC-721 standard are embedded with identifiable information that gives each NFT a unique identity, thus allowing participants to trace the product flow by tracking the ownership history of their respective NFT [30]. Our solution has four core smart contract components: seed cotton NFT contracts, lint NFT contracts, inspection NFT contracts and a market management smart contract system. Among them, the ERC-721 standard-based smart contracts are responsible for generating, authorising and transferring different NFTs, while the marketplace SC focuses on managing and facilitating the trading activities of these NFTs.
* Interplanetary file system: We use a distributed storage solution based on content addressing with version control and a peer-to-peer hypermedia architecture for the storage of NFT-associated metadata. In the NFT ecosystem, the IPFS ensures that each file possesses uniqueness within the global namespace by using content identifiers (CID) [31]. All files and directories uploaded to the IPFS are indexed and located based on their cryptographic hash values. This mechanism enables all relevant stakeholders to access the file resources stored on the IPFS. At the NFT application level, the IPFS hosts detailed metadata related to the cotton lint's quality certification and transaction history, thus ensuring secure storage and transparent access to this crucial data.
* Decentralised applications: In the cotton lint supply chain, stakeholders interact with smart contracts through DApps. With this platform, users can manage NFT assets on their personal account pages and buy or sell products on the marketplace homepage, thus enabling the flexible manipulation and circulation of NFT resources [32].