Patent ID: 7484092

Claim:
A method of searching a plurality of encrypted files for which a data structure storing information related to contents of the plurality of encrypted files is provided, the method comprising: receiving information identifying a query element; determining a first set of files from the plurality of encrypted files wherein membership of the first set is based upon the query element and unencrypted information from the data structure, the first set of files comprising less than all of the plurality of encrypted files; decrypting each file in the first set of files; searching each decrypted file in the first set of files to identify a second set of files including files that contain the query element, wherein the search is performed using an unencrypted form of the query element, wherein the second set of files is a subset of the first set and identification is based on matching the unencrypted form of the query element with unencrypted data determined after the decrypting step, wherein the second set of files comprises a fewer set of files for at least one instance of the query element such that the first set of files can contain a document that does not contain the at least one instance of the query element; and outputting information identifying files in the second set of files, wherein the plurality of encrypted files are partitioned into entities according to a size parameter, each entity comprising portions of one or more files from the plurality of encrypted files, and at least one entity comprising portions of two or more files from the plurality of encrypted files.