Cloud computing offers the opportunity of data outsourcing as well as data management. However, because of various privacy issues, confidential data must be encrypted before being outsourced to the cloud. But query processing over encrypted data without decrypting data is a very challenging task. Property-preserving encryption schemes allow encrypting data while still enabling efficient querying over encrypted data. The inherent merits of property-preserving encryption schemes make them very

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... table and efficient for cloud data outsourcing. However, the security of such schemes is still a challenge because they are vulnerable to statistical attacks. We present a new order-preserving scheme for indexing encrypted data, as an alternative to propertypreserving schemes, which hides data frequency to achieve a strictly stronger notion of security. The proposed indexing method is secure against statistical attacks. Hence, data cannot be recovered from indexes. Moreover, our scheme is still efficient for query processing.