20100045794 | METHOD FOR MARKING A DIGITAL IMAGE WITH A DIGITAL WATER MARK - The invention relates to a method for marking a digital document, especially a digital image, with a digital watermark for the purpose of manipulation recognition while inserting an integrity information and at least one multibit message. The method according to the invention comprises the following steps: converting the digital image to a converted digital image; dividing up the converted digital image into a plurality of blocks, every block having a plurality of coefficients; establishing a plurality of mapped message values for the at least one message, a plurality of first coefficients being mapped onto a vector that depends on a secret key; inserting every bit of every message into at least one of the mapped message values; establishing a plurality of mapped integrity values for the integrity information, a plurality of second coefficients being mapped onto a message-dependent vector, said message-dependent vector being derived from at least one of the messages and the secret key; inserting every piece of the integrity information into at least one of the mapped integrity values; updating every first coefficient that is used for establishing the mapped message values, using the inserted mapped message values, thereby achieving that the mapping of the updated first coefficients onto the secret key-dependent vector and the inserted mapped message values is identical; and updating every second coefficient that is used to calculate the mapped integrity values, using the inserted mapped integrity values, thereby achieving that the mapping of the updated second integrity coefficients onto the message-dependant vector and the inserted mapped integrity values is identical. | 02-25-2010 |