Blockchain-based searchable encryption with efficient result verification and fair payment

Abstract

Data outsourcing has become a popular application. Searchable encryption (SE) can provide data retrievability as well as keep data privacy. In the threat model of SE schemes, the cloud server is usually assumed to be Honest-But-Curious, but this may not be true in reality. The blockchain-based SE makes malicious cloud servers dare not to deviate from the protocol, and search results are validated by miners. However, rational miners would skip the validation step and accept the block directly to save computational resources. This situation is called the Verifier’s Dilemma which will make the blockchain-based SE scheme not real verifiable. Therefore, this paper proposes a verifiable blockchain-based public-key encryption scheme that outsources the verification to the TrueBit network. This design makes our scheme achieves effective verifiability which will minimize the computational cost of miners. Furthermore, our scheme also establishes a fair payment protocol between the multiple data owners and data users. Also, the data owner can revoke the permission of the document he/she shared before. We also present security proofs and analysis of the proposed scheme. Performance evaluation presents the overheads of performing search operations on the cloud server and conducting transactions on smart contracts in Ethereum. The experiment results demonstrate the practicability of our proposed scheme.