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On query execution over encrypted data



To ensure the confidentiality of the encrypted data in a database-as-a-service model, the sensitive data need to be encrypted. When this encrypted data are queried, complete record has to be decrypted to fetch the actual results. This paper is concentrating on improving the performance of different query operations, that is, non-aggregate, aggregate, and user-defined query operations on encrypted data. The performance of these query operations over the encrypted data is compared with that of the available methods in terms of the execution time, and it is found that the efficiency of the proposed approach is better than that of the traditional approach. Effectiveness of different types of non-aggregate query operations is identified in terms of filter ratio and false ratio. The analysis has shown that the filter ratio increases and the false ratio decreases with increase in size of sensitive string and the reachability matrix generated for non-aggregate attribute. Copyright © 2014 John Wiley & Sons, Ltd.