A method for encrypting a database includes the following step. Keywords in the database are encrypted to obtain encrypted search tags for the keywords. A table of reverse indices is generated for the encrypted search tags. A table of cross keyword indices is generated. A method for searching in an encrypted database includes the following steps. A search is formulated as a conjunct of two or more atomic search queries. One of the conjuncts is selected as a primary atomic search query. Search capabilities are generated for a secondary atomic search query using the primary atomic search query and the secondary atomic search query. Such methods mask query data and the actual composition of the database to reduce computation complexity and privacy leakage.