A system for handling files containing digitized images, such as digitized bank checks. Four digitized image-files are obtained for each check: front and back at the beginning of a process, and front and back at the end of the process. Four digital signatures are generated, one for each image-file. The four image-files are to be consolidated into a single composite file. However, for technical reasons, the content of the image-files must be altered somewhat. Thus, if the image-files are later extracted from the composite file, the extracted files will not correspond to the original image-files, and will produce different digital signatures. The invention allows the original image-files to be accurately extracted from the composite file.