| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a further effective method for continuously safeguarding and at the same time protecting a digital asset. <P>SOLUTION: When a safeguarded file is secret even if a proper access right is given, at least a security use permission key is required. The secured file has two portions, namely a header portion and a secured data portion. The header includes security information that indicates or includes an access rule, a protection key, and a file key. The access rule facilitates access to the safeguarded data portion, and determines who can substantially access a safeguarded document. The file key is used for enciphering/decoding the safeguarded data section, and is protected by the protection key. When contents in the safeguarded file are handled secretly, the file key is protected jointly not only by the use permission key but also by the protection key regarding a user who tries to access the safeguarded file. <P>COPYRIGHT: (C)2003,JPO</p> |
