Privacy-Preserving Searchable Encryption Framework for Permissioned Blockchain Networks

Enabling keyword search directly over the data stored on the blockchain is a desirable technique that can help in the effective utilization of the data while preserving the privacy. Searchable Encryption (SE) is a well-known technique that allows search queries over the encrypted Cloud data, however, existing solutions are based on the assumption of the Cloud Server being "trusted-but-curious" or "honest-but-curious". This leads to a compelling case to use permissioned blockchain technology to ensure greater levels of security when the Cloud Server is malicious. The amalgamation of SE and permissioned blockchain empowers a client to place complete trust on the Cloud Server and the services it has to offer. This paper presents a novel privacy-preserving framework to facilitate keyword search over encrypted data stored on the blockchain network. The framework for the first time studies SE over a permissioned blockchain network i.e., Hyperledger-Fabric. The SE scheme is privacy-preserving as it is based on probabilistic trapdoors. As a result the framework guarantees prominent security and privacy gains.