| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an apparatus whereby no unequal security of keys used for making information (contents) to be protected available is caused among terminals, the unequal security caused by differences of frequencies of use of the information to be protected among the terminals. <P>SOLUTION: In order to solve the problem, the management apparatus is utilized, which comprises: a second key generation section; a use condition information update section; and a first key generation information re-encryption section or the like. The second key generation section generates a second key on the basis of use condition information. The use condition information update section updates the use condition information. The use condition information is updated not always by the use of the contents but by various triggers (or causes). Then the second key generation section generates a new second key on the basis of the updated use condition information, and the first key generation information re-encryption section uses the new second key to re-encrypt first key generation information. That is, the apparatus is characterized in that the second key is updated accompanied by the update of the use condition information. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
