Patent ID: 7356148

Claim:
An information processing method of receiving encoded image data compression-coded for each spatial rectangle region that constitutes an image and encrypting the encoded image data, characterized by comprising: repeatedly forming one spatial rectangle region group from a plurality of adjacent spatial rectangle regions and another spatial rectangle region group from a plurality of adjacent spatial rectangle region groups so as to define a hierarchical structure of spatial rectangle region groups, dividing encoded data of a spatial rectangle region located at a terminal of the hierarchical structure into a plurality of partial encoded data regarding resolution or quality, and arranging the partial encoded data toward the terminal in descending order based on the resolution or quality so that partial encoded data of lowest resolution or lowest quality is arranged at the terminal of the hierarchical structure, thereby defining a tree structure that has as nodes the respective spatial rectangle region groups, the respective spatial rectangle regions, and the respective partial encoded data; assigning identification information uniquely identifying each node to each node in the hierarchical structure; generating encryption key information for a node located at an uppermost layer of the tree structure for an entire image expressed by the encoded image data; executing, up to a node located at the terminal, processing for generating encryption key information for a node of interest on the basis of encryption key information generated for a node located at an upper layer, identification information assigned to the node of interest and a one-way function, so as to generate the encryption key information for each node; designating, in the tree structure, the position of a desired node among the plurality of partial encoded data; setting, as an object to be encrypted, partial encoded data designated in said designating step and partial encoded data at a higher layer than the layer of the designated partial encoded data; and encrypting each partial encoded data set in said setting step using the generated encryption key information corresponding to each node.