## 2 The Related Literature  
### NFTs and Traditional Tokens  
The origin of NFT can be traced back to \"colorful coins\", a method of representing real-world assets on the Bitcoin blockchain [17], including digital and physical assets. However, due to the limitations of the Bitcoin scripting language, the functionality of colored coins is limited [18]. Therefore, a more scalable blockchain has been proposed and continuously developed--the Etherchain. According to [PERSON], the founder of Ethereum, his main motivation for developing Ethereum was that \"the concept of blockchain can be used for more than just money\" [19]. Ethereum represents a blockchain with a built-in Turing complete programming language. It provides an abstract layer that allows anyone to write smart contracts and decentralized applications, where they can create their own arbitrary rules, including ownership rules, transaction formats, and state transition functions [20]. Of course, beyond the Ethereum blockchain, emerging blockchains such as Flow, Tezos, and Algorand have also been increasing their support for NFT. The introduction and adoption of smart contract interface standards have aided the development process of decentralized applications. This has facilitated a consistent application interaction, as well as creating, managing, and transferring tokens in a universal and uniform way [21]. ERC20 [22] and ERC721 [23] are the two most popular standards. ERC-20 is the standard interface for Ethereum-issued tokens, providing interoperability and fungibility to tokens. ERC721 standard was introduced by [PERSON], a contributor to the Ethereum source code library and founder of the digital collectibles game CryptoKitties. It established the concept and status of NFTs, known as the \"gold standard\" [24]. On the basis of ERC-20, ERC-721 has added interfaces such as tokenId and ownerOF, which endowed each token with unique and indivisible characteristics and left the initial impression of NFT on the public. In addition to these two standards, other standards such as ERC-998 (composite NFTs) [25], ERC-1155 (semi fungible Token) [26], and ERC-725 (attachable data key/value store) [27] are also constantly innovating and reshaping the creative space of NFTs. Tokens are a type of digital asset issued on blockchain technology, which can represent a certain equity, value, or physical object. According to actual functions, tokens are divided into three categories: payment tokens, utility tokens, and asset tokens [28; 29]. Table 1 provides a comparative analysis of them. Payment tokens, also known as cryptocurrencies or fungible tokens, are mainly used to pay for goods or services. Utility tokens are designed to provide digital access to an application or service. Asset tokens refer to broad tradable assets with investment or collection attributes, including security tokens and NFTs. Compared to payment tokens, NFTs have uniqueness, cannot be replaced with each other, cannot be divided, and do not have payment functionality. Compared with securities tokens with investment attributes, NFTs have a more prominent collection attribute and are not security vouchers with a certain future cash flow, and they cannot be considered financial products. Similar to traditional tokens, research on NFT is mainly distributed in the three fields of economics and finance, computer science, and law [30], focusing on the market, technology, and legal risks they face. Under the theme of market risk, scholars use economic and financial methods to explore the value of NFT. Research shows that in the early market, the price of NFT showed inefficiency, and the value steadily increased [31]. In addition, factors such as the situation of the cryptocurrency market [32], macroeconomic conditions, and public attitudes [33] are related to the value of NFT. Under the theme of technological risk, scholars are committed to developing and improving computer science technology.