Searchable encryption allows a secret key holder to issue search tokens for keywords that enable other parties to perform equality comparisons with ciphertexts. Assume a set of text documents with overall w keywords where each document is associated with m of these (possibly identical) keywords. A querier is asking the secret key holder to issue him a search token t for n distinct keywords. The ciphertext of a document matches the search token if the set of n keywords of the search token is a subset of the set of m keywords of the document. Searchable encryption has many practical applications.