A system, method, computer program product, and data management service that allows any comparison operation to be applied on encrypted data, without first decrypting the operands. The encryption scheme of the invention allows equality and range queries as well as the aggregation operations of MAX, MIN, and COUNT. The GROUPBY and ORDERBY operations can also be directly applied. Query results produced using the invention are sound and complete, the invention is robust against cryptanalysis, and its security strictly relies on the choice of a private key. Order-preserving encryption allows standard database indexes to be built over encrypted tables. The invention can easily be integrated with existing systems.