BBS: A secure and autonomous blockchain-based big-data sharing system

Chain of custody is needed to document the sequence of custody of sensitive big data such as various healthcare data. In this work, we propose a secure and autonomous big data sharing system (BBS) based on a permissioned blockchain. In our system, we refer to the data stored at a blockchain node but outside the ledger for sharing as “off-state”, such as the large amounts of data (called “big data”) that cannot be stored directly in a blockchain ledger in practice. To securely and autonomously share the off-state data, we further design an off-state sharing protocol. In the proposed protocol, a sender registers the big data with BBS for sharing. To acquire the big data, an authenticated and authorized receiver has to propose transactions and interact with BBS in five phases, including data transfer authorization, data transfer, two-time key request, and data decryption. The key advantage of BBS is its ability to defeat dishonest users and autonomously perform the aforementioned five phases. The corresponding transactions are recorded in the ledger, serving as chain of custody evidences that document the data trail. To demonstrate the effectiveness of our proposed system, we have designed and implemented prototypes of BBS for sharing big files over two representative permissioned blockchains, i.e., Hyperledger Fabric and Enterprise Ethereum. Extensive experiments are performed to validate the feasibility and performance of our system.