Patent ID: 7447314

Claim:
An information processing method of encrypting encoded image data including encoded data of each rectangle region obtained by dividing an image into N rectangle regions, encoded data of each rectangle region including data corresponding to each resolution of M resolutions arranged in ascending order of resolution or including data corresponding to each image quality of M qualities arranged in ascending order of image quality, comprising: a step of generating a key K unique to the encoded image data; a step of calculating, as a key KT n unique to a rectangle region n, an output value obtained by inputting an index n (n=1 to N) of the rectangle region n and the key K into a one-way function; a step of dividing encoded data of the rectangle region n into data D nm (m=1 to M) for each resolution or each image quality, wherein the data D nm having a smaller value for m is data of higher resolution or higher image quality; a step of generating a key KT nm unique to the data D nm , wherein the key KT nm =KT n if m=1, and the key KT nm =H(KT nm−1 ) using a one-way function H if m>1; and a step of encrypting the data D nm using the key KT nm .