A method comprises receiving, by a processor, a copy of a database containing records, each record having a plurality of attributes. The method also comprises determining, by the processor, whether a first attribute in each record results in a predetermined value in modulo P when hashed with a key and determining, by the processor, whether a second attribute in each record results in the predetermined value in modulo P when hashed with a key. For a first record whose first attribute results in the predetermined value in modulo P when hashed with a key and a second record whose second attribute also results in the predetermined value in modulo P when hashed with a key, the method further comprises swapping by the processor the second attributes between the first and second records.