	US 7,581,115 B2
	Information processing method, apparatus, and information processing program
Junichi Hayashi, Kanagawa-ken (Japan); and Yuji Suga, Kanagawa-ken (Japan)
Assigned to Canon Kabushiki Kaisha, Tokyo (Japan)
Appl. No. 10/538,839 PCT Filed Jan. 23, 2004, PCT No. PCT/JP2004/000619 § 371(c)(1), (2), (4) Date Jun. 13, 2005, PCT Pub. No. WO2004/066552, PCT Pub. Date Aug. 05, 2004.
Claims priority of application No. 2003-015233 (JP), filed on Jan. 23, 2003.
Prior Publication US 2006/0069964 A1, Mar. 30, 2006
Int. Cl. G06F 11/30 (2006.01); G06F 12/14 (2006.01); G08C 25/00 (2006.01)

U.S. Cl. 713—189 [726/26; 714/758; 714/799]

6 Claims

1. An information processing method for decrypting encrypted encoded image data comprising steps of:

receiving the encrypted encoded image data and corresponding header data, the header data including a first field storing information indicating whether the encoded image data has an error detecting code for detecting an error in the encoded image data, wherein the first field is referenced by a decoding process, and a second field storing information indicating whether the encoded image data has the error detecting code for detecting the error in the encoded image data, wherein the second field is not referenced by the decoding process;

determining, based on the information stored in the second field, whether the encrypted encoded image data includes an error-detecting code;

determining whether key information required to decrypt the encrypted encoded image data is available;

modifying the first field to store information indicating that the encrypted encoded image data includes the error detecting code, if the information stored in the second field indicates that the encrypted encoded image data includes the error detecting code and the key information is available,

wherein, if the information stored in the second field does not indicate that the encrypted encoding image data includes the error detecting code and the key information is available, the first field is not modified, and

wherein, if the key information is not available, the first field is not modified;

decrypting the encrypted encoded image data to generate encoded image data, if the information stored in the second field indicates that the encrypted encoded image data includes the error detecting code and the key information is available; and

decrypting the encrypted encoded image data, if the information stored in the second field does not indicate that the encrypted encoding image data includes the error detecting code and the key information is available,

wherein, if the key information is not available, the encrypted encoded image data is not decrypted performing all of the above steps using at least one processor.