Abstract: A search system includes a storage device and a search server. The storage device stores an index database storing an index encrypted with an index key and the index key encrypted with a user key and associated with the encrypted index and stores a document database storing a document encrypted with a document key and the document key encrypted with the user key and associated with the encrypted document. The search server extracts a term for search from a requested search query, decrypts the encrypted index key with a user key which belongs to a user requesting the search query, encrypts the extracted term with the decrypted index key without storing the decrypted index key in a non-transitory storage device, searches the index database with the index encrypted using the encrypted first term, and sends a search result to a terminal.

Abstract: A search system includes a storage device and a search server. The storage device stores an index database storing an index encrypted with an index key and the index key encrypted with a user key and associated with the encrypted index and stores a document database storing a document encrypted with a document key and the document key encrypted with the user key and associated with the encrypted document. The search server extracts a term for search from a requested search query, decrypts the encrypted index key with a user key which belongs to a user requesting the search query, encrypts the extracted term with the decrypted index key without storing the decrypted index key in a non-transitory storage device, searches the index database with the index encrypted using the encrypted first term, and sends a search result to a terminal.

Abstract: To reduce the size of backup data, increase the backup speed, and solve a problem that the amount of unnecessary writing could undesirably increase in a restoration process, which would otherwise require physical disks with a capacity greater than the size of a virtual volume. On a backup server having mounted thereon a virtual volume that is the target to be backed up and restored, read/write access to only the blocks of data areas is performed by a device driver that filters I/O access to a device from a file system on the basis of the data mapping information of the virtual volume, whereby read/write access to unnecessary portions is avoided. Thus, it is possible to reduce the size of backup data, increase the backup speed, and prevent an increase in the amount of unnecessary writing to the virtual volume in a restoration process.