Patent ID: 8055900

Claim:
A digital data providing apparatus comprising: an inputting unit that inputs digital image data; a processing unit that performs a JPEG compression process or a tonal level conversion process on the digital image data; a calculating unit that calculates an index value for the processed digital image data, wherein the index value is one of a Signal to Notice Rate (SNR), a Peak Signal to Notice Rate (PSNR), a Perceptive Evaluation Level (PEL), and a Just Noticeable Difference (JND); a judging unit that judges whether or not the process performed on the digital image data by the processing unit involves falsification, by comparing the index value calculated by the calculating unit with a predetermined value; a signature generating unit that generates a digital signature from the digital image data input by the inputting unit, if it is judged by the judging unit that the process performed on the digital image data by the processing unit does not involve falsification, and does not generate the digital signature if it is judged that the process involves falsification, wherein the digital signature is generated by (a) sequentially comparing bit planes of the digital image data inputted by the inputting unit with bit planes of the processed digital image data, from the bit plane near the most significant bit (MSB) toward the bit plane near the least significant bit (LSB), and using the bit planes having the same values to generate the digital signature, or (b) sequentially comparing frequency components converted from the digital image data inputted by the inputting unit with frequency components converted from the processed digital image data, from the high frequency components toward the low frequency components, and using the components having the same values to generate the digital signature; and an outputting unit that outputs the digital image data processed by the processing unit and the digital signature generated by the signature generating unit, wherein at least the processing unit, the calculating unit, and the signature generating unit are implemented by a CPU in the digital data providing apparatus.