1. A computer-implemented method, comprising steps of: separately encrypting a set of plain text data using two or more encryption functions, thereby producing an encrypted domain comprising at least two distinct groups of encrypted data items, wherein the two or more encryption functions comprise (i) a brute force safe function and (ii) a range safe function; converting a range query over plain text data items into a query over at least one of the distinct groups of encrypted data items; and combining results from the query over the distinct groups of encrypted data items, thereby generating a final encrypted result to the range query; wherein the steps are carried out by at least one computing device.