Information processing method, apparatus, and information processing program
Even when encoded (compressed) image data appended with an error-detecting code is encrypted, the apparatus which receives and reproduces that image data can execute a normal process without any insignificant re-send request and the like. To this end, encoded image data is input, and first error-detecting encoding information contained in its header is checked to determine whether or not an error-detecting code is appended. If it is determined that the error-detecting code is appended, the first error-detecting encoding information is changed to indicate the absence of an error-detecting code, and is saved as second error-detecting encoding information. Then, the encoded image data is encrypted.
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.
2. The method according to claim 1 , wherein the first field is included in a main header defined in the JPEG 2000 standard format and the second field is included in a comment defined in the JPEG 2000 standard format.
3. An information processing apparatus for decrypting encrypted encoded image data, the apparatus comprising:
an input unit that receives 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;
a first determination unit that determines, based on the information stored in the second field, whether the encrypted encoded image data includes an error-detecting code;
a second determination unit that determines whether key information required to decrypt the encrypted encoded image data is available;
a modification unit that modifies 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;
a decryption unit that decrypts 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 that decrypts 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.
4. The information processing apparatus according to claim 3 , wherein the first field is included in a main header defined in the JPEG 2000 standard format and the second field is included in a comment defined in the JPEG 2000 standard format.
5. A computer-readable storage medium storing a program which, when executed, performs 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.
6. The computer-readable storage medium according to claim 5 , wherein the first field is included in a main header defined in the JPEG 2000 standard format and the second field is included in a comment defined in the JPEG 2000 standard format.