| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To dispense with controlling a plurality of keys with respect to picture data having a plurality of tiles and a plurality of hierarchical structures even when encryption is made by using a different encryption key for every tile and every hierarchical structure. <P>SOLUTION: A code stream c compressed and coded in tile units is input. An encryption tile part designation section constitutes one tile group with a plurality of adjacent tiles and in addition, repeats the constitution of another tile group with the adjacent tile groups to define the hierarchical structure of the tile groups. In such a case, what tile group in what hierarchy should be involved in encryption is determined and output as encryption tile information ta. Meanwhile, a key matrix generation section 12 generates an encryption key ck for the entire input code stream c, successively generates the encryption key for each node in the hierarchical structure, and outputs the result as a key matrix ka. An encryption section 13 enciphers a tile being an encryption object by using a key generated for the tile and outputs an enciphered code stream c'. <P>COPYRIGHT: (C)2004,JPO</p> |
