| 摘要 |
<P>PROBLEM TO BE SOLVED: To actualize a hierarchial multicast distribution for controlling the quality and/or the resolution of video images for each recipient. <P>SOLUTION: In applying broadcast encryption (decryption) to a hierarchical encoding strategy for image data, etc., suitable for multicast distribution, the method generates a secret key of an upper layer subordinately from a secret key (master key) corresponding to a lower layer hierarchy image by using a one-way hash function, as for a plurality of secret keys required for each image of different stage. Moreover, a secret key in relation to the identical hierarchy image but different for each individual person is owned by each individual person in a mutually overlapped fashion. Further, only a public key for broadcast encryption and an individual secret key corresponding to the lowest hierarchy image are owned by each individual person, and a common key corresponding to each hierarchy is generated from the individual secret key according to the one-way hash function. <P>COPYRIGHT: (C)2010,JPO&INPIT |
