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Recent research has demonstrated searchable blockchains that not only provide reliable search over encrypted distributed storage systems but ensure privacy is preserved. Yet, current solutions focus on single-keyword search over encrypted data on the blockchain. To extend such approaches to multi-keyword scenarios, they essentially perform a single-keyword search for multiple times and take the intersection of the results. However, such extensions suffer from privacy and efficiency issues. In particular, the service peers, which process the search requests, will be aware of the intermediate results, which include the data associated with each of the encrypted keywords. Moreover, these multiple traversals incur long delays in performing the search requests one after another with an extra cost in calculating the intersection of multiple sets. Finally, the service peers will charge the data owner a lot for writing the vast …