BDTS: A Blockchain-based Data Trading System with Fair Exchange

Trading data through blockchain platforms is hard to achieve \textit{fair exchange}. Reasons come from two folds: Firstly, guaranteeing fairness between sellers and consumers is a challenging task as the deception of any participating parties is risk-free. This leads to the second issue where judging the behavior of data executors (such as cloud service providers) among distrustful parties is impractical in traditional trading protocols. To fill the gaps, in this paper, we present a \underline{b}lockchain-based \underline{d}ata \underline{t}rading \underline{s}ystem, named BDTS. The proposed BDTS implements a fair-exchange protocol in which benign behaviors can obtain rewards while dishonest behaviors will be punished. Our scheme leverages the smart contract technique to act as the agency, managing data distribution and payment execution. The solution requires the seller to provide consumers with the correct decryption keys for proper execution and encourages a \textit{rational} data executor to behave faithfully for \textit{maximum} benefits. We analyze the strategies of consumers, sellers, and dealers based on the game theory and prove that our game can reach the subgame perfect Nash equilibrium when each party honestly behaves. Further, we implement our scheme based on the Hyperledger Fabric platform with a full-functional design. Evaluations show that our scheme achieves satisfactory efficiency and feasibility.