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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.

Privacy preserved outsourced data access control is a hard task under the control of third–party storage server. To overcome obstacles in the third party based scenario, Attribute-based signcryption system with bilinear pairing tool is one of the most suitable methods in cloud. It maintains the basic features of security like, authenticity, confidentiality, public verifiability, owner privacy, etc. Although, this method has some challenges like a centralized authority used for user secret key generation for de-signcryption operation, and lack in competent attribute revocation. To overcome the issues, we have proposed a scheme of attribute revocable privacy preserved outsourced based data access control mechanism using Attribute-based signcryption. The proposed method allows multi-authorities for assigning both attribute and secret keys for users along with trusted certified authority, which provides security parameters. The analysis of the proposed method shows less computation cost in decryption and authentication verification. The almost same performance and efficiency is found while comparing with the existing schemes after adding new features. [ABSTRACT FROM AUTHOR]