Fair Data Trading Protocol based on Passive Proxy Re-encryption with Smart Contracts

With the diversity of data generated in daily life and the high economic benefits of effective use of data in various aspects, data trading has become a trend, and the fairness of data trading has also received increasing attention in recent years. Fairness means that the buyer and seller either get what they want or neither, which is one of the most basic requirements of transactions. Studies have shown that it is difficult to design a fair agreement based on buyers and sellers alone. Therefore, existing fair agreements generally rely on Trusted Third Parties (TTP) for transactions, and their fairness is based on the behavior of TTP and the trust of both parties in TTP. After the emergence of blockchain and smart contracts, their decentralization and transparency make them excellent candidates for replacing TTP. Therefore, this paper attempts to design a secure and fair data transaction protocol based on smart contracts. In order to ensure the security of data, we use an advanced Passive Proxy Re-Encryption (PPRE) scheme to enable the smart contract to transfer the decryption right to the buyer after receiving the buyer’s payment. In addition, based on smart contracts and PPRE, a fair protocol for data trading is proposed, and the fairness of the protocol is guaranteed by an arbitration protocol. The protocol supports ciphertext publicity and repeatable sale, thereby reducing the number of interactions. Comprehensive experimental results verify the feasibility and effectiveness of the proposed protocol.