A method of securely storing electronic information includes a step in which target electronically stored information is encrypted with a first encryption key and then partitioned into a first set of encrypted ESI partitions a subset of which is able to reconstruct the unpartitioned encrypted ESI. This...http://www.google.com.tw/patents/US8150038?utm_source=gb-gplus-share專利 US8150038 - Revocation of a system administrator in an encrypted file system
