Data sharing is ubiquitous in the metaverse, which adopts blockchain as its foundation. Blockchain is employed because it enables data transparency, achieves tamper resistance, and supports smart contracts. However, securely sharing data based on blockchain necessitates further consideration. Ciphertext-policy attribute-based encryption (CP-ABE) is a promising primitive to provide confidentiality and fine-grained access control. Nonetheless, authority accountability and key abuse are critical issues that practical applications must address. Few studies have considered CP-ABE key confidentiality and authority accountability simultaneously. To our knowledge, we are the first to fill this gap by integrating non-interactive zero-knowledge (NIZK) proofs into CP-ABE keys and outsourcing the verification process to a smart contract. To meet the decentralization requirement, we incorporate a decentralized CP-ABE scheme into the proposed data sharing system. Additionally, we provide an implementation based on smart contract to determine whether an access control policy is satisfied by a set of CP-ABE keys. We also introduce an open incentive mechanism to encourage honest participation in data sharing. Hence, the key abuse issue is resolved through the NIZK proof and the incentive mechanism. We provide a theoretical analysis and conduct comprehensive experiments to demonstrate the feasibility and efficiency of the data sharing system. Based on the proposed accountable approach, we further illustrate an application in GameFi, where players can play to earn or contribute to an accountable DAO, fostering a thriving metaverse ecosystem.

翻译：数据共享在元宇宙中无处不在，而元宇宙以区块链为基础。采用区块链是因为它能实现数据透明性、达到防篡改性并支持智能合约。然而，基于区块链的安全数据共享仍需进一步考量。密文策略属性基加密（CP-ABE）是一种能提供机密性和细粒度访问控制的前沿密码原语。然而，权威机构问责与密钥滥用是实际应用必须解决的关键问题。现有研究很少同时考虑CP-ABE密钥的机密性与权威机构问责。据我们所知，我们首次通过将非交互式零知识（NIZK）证明集成到CP-ABE密钥中，并将验证过程外包给智能合约，填补了这一空白。为满足去中心化要求，我们将一种去中心化CP-ABE方案纳入所提出的数据共享系统。此外，我们提供了一种基于智能合约的实现，用于判定一组CP-ABE密钥是否满足访问控制策略。我们还引入了一种开放的激励机制，以鼓励诚实地参与数据共享。因此，密钥滥用问题通过NIZK证明和激励机制得以解决。我们提供了理论分析并进行了全面实验，以证明该数据共享系统的可行性与效率。基于所提出的可问责方法，我们进一步阐述了其在GameFi中的应用场景：玩家可通过游戏赚取收益或为一个可问责的DAO做出贡献，从而促进繁荣的元宇宙生态系统。