Digital signature method for images without additional files, robust to JPEG compression and metadata removal

The article discusses a method for digitally signing images that does not use metadata or additional files. The method is resistant to jpeg compression. The object of the digital signature is 8x8 pixel blocks after a discrete cosine transform applied, which make up the jpeg file. A method to achieve resistance to jpeg compression is to quantize (reduce the precision) of the values in the blocks so that when calculating the signature, they remain unchanged up to a certain compression level.