Toward Achieving Anonymous NFT Trading

With the rapid development of Non-Fungible Token (NFT) market, various types of digital artwork are published via NFT in recent years for sale. In the current NFT system, owner’s address of each NFT is stored in plaintext. This leads to a severe privacy problem: once a person’s blockchain address is known, all his NFT assets are viewable, which may further cause problems related to the privacy of holding sensitive NFT or premeditated scams to high-value NFT owners. However, due to the limitation of Ethereum and smart contract, it is hard to prevent others from tracking the owner of NFT. Meanwhile, current state-of-the-art NFT research usually assumes the relation between blockchain address and owner’s identity is unknown, thus creating the so-called anonymity. In this paper, based on the most popular NFT marketplace OpenSea’s system, we propose a new exchange scheme to hides the address of NFT owner during trading. To achieve our goal, a proof of commitment scheme is exploited to bind the owner to an NFT while hiding the identity. Moreover, An anonymous payment method is designed to prevent attackers from tracing the Ether flow in NFT trading. Our scheme is proven to be secure against curious users and malicious active attackers. Implementation on testnet also shows that the increased gas cost is acceptable, meaning it is suitable for application.