V2FS: A Verifiable Virtual Filesystem for Multi-Chain Query Authentication

The rise of decentralized finance (DeFi), Web 3.0, and other blockchain-based applications has led to an increased demand for on-chain data analysis across multiple blockchains. Conducting advanced queries, such as data aggregation and correlation analysis, is essential for gaining valuable insights in this context. However, multi-chain queries pose several challenges for the querying system, including compatibility with existing blockchains, supporting diverse query types, and ensuring the integrity of query results. To tackle these challenges, we propose a novel paradigm called verifiable virtual filesystem (V2FS). V2FS extends the POSIX I/O interface, shifting the focus from verifying computation to verifying data. This innovative approach empowers query clients to leverage an off-the-shelf database engine to evaluate queries using verifiable data retrieved from an indexing service provider (ISP). Our solution ensures strong integrity guarantees and can be smoothly integrated with existing database engines to support various query types. To achieve blockchain compatibility, we utilize the DCert framework to certify blocks from different blockchains, making our system applicable to various blockchain systems. Furthermore, we propose cache-based algorithms and a bloom filter-integrated algorithm to optimize query performance and minimize network communication costs. Security analysis and empirical study validate the effectiveness and efficiency of the proposed system.