VQL: Efficient and Verifiable Cloud Query Services for Blockchain Systems

Haotian Wu, Zhe Peng, Songtao Guo, Yuanyuan Yang, Bin Xiao*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

58 Citations (Scopus)


Despite increasingly emerging applications, a primary concern for blockchain to be fully practical is the inefficiency of data query. Direct queries on the blockchain take much time by searching every block, while indirect queries on a blockchain database greatly degrade the authenticity of query results. To conquer the authenticity problem, we propose a Verifiable Query Layer (VQL) that can be deployed in the cloud to provide both efficient and verifiable data query services for blockchain systems. The middleware layer extracts data from the underlying blockchain system and efficiently reorganizes them in databases. To prevent falsified data from being stored in the middleware, a cryptographic fingerprint is calculated based on each constructed database. The database fingerprint will be first verified by miners and then written into the blockchain. Moreover, public users can verify the entire databases or several databases that interest them in the middleware layer. We implement VQL together with the verification schemes and conduct extensive experiments based on a practical blockchain system. The evaluation results demonstrate that VQL can efficiently support various data query services and guarantee the authenticity of query results for blockchain systems.
Original languageEnglish
Pages (from-to)1393-1406
Number of pages14
JournalIEEE Transactions on Parallel and Distributed Systems
Issue number6
Early online date20 Sept 2021
Publication statusPublished - 1 Jun 2022

Scopus Subject Areas

  • Signal Processing
  • Hardware and Architecture
  • Computational Theory and Mathematics

User-Defined Keywords

  • blockchain systems
  • Cloud query service
  • data authenticity
  • verifiable query
  • Costs
  • Distributed ledger
  • Bitcoin
  • Blockchains
  • Peer-to-peer computing
  • Data mining
  • Middleware


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