| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To enable it to obtain high cipher strength, without being dependent on memory management method of a system. <P>SOLUTION: If a term of an arbitrary encryption key invalidates, a re-encryption instruction of data for re-encryption is outputted from a re-encryption means 57, as data for re-encryption, an encryption data enciphered by the encryption key to which the term was invalidated. Then, the encryption key made to correspond to the attributes of data for re-encryption is changed and the encryption key after changing is formed. Moreover, a decoding key according to the attributes of data for re-encryption is formed.When all the datas for re-encryption were decoded, a decoding key made to correspond to the attributes of data for re-encryption is changed. Next, the data for re-encryption is decoded using the decoding key in an encoding means 54a and is passed to an encryption means 53a. And, the data for re-encryption is enciphered using the encryption key after changing by an encryption means 53a. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
