Patent ID: 7362860

Claim:
An image data encryption method of encrypting encoded image data which is constituted by a plurality of encoded data blocks, comprising: a step of inputting one of the plurality of encoded data blocks; a determination step of determining whether the data block inputted in said inputting step is an object to be encrypted; an encryption step of encrypting the data block when it is determined in the determination step that the data block as-is the object to be encrypted; a discrimination step of discriminating whether the data block is an object to be reproduced at a decoder in a scrambling mode or in a non-scrambling mode; and an addition step of adding terminating information to a starting position of the data block encrypted in the encryption step if it is discriminated in the discrimination step that the data block is an object to be reproduced in the non-scrambling mode, and adding the terminating information to an ending position of the data block encrypted in the encryption step if it is discriminated in the discrimination step that the data block is an object to be reproduced in the scrambling mode, wherein the terminating information is used to notify the decoder to not perform decoding for the subsequent data to the end of the data block.