The cost of digital dental X-ray equipment is still too high for many clinical dental departments. When considering the balance of cost and effectiveness for clinical dental departments, using a scanner to scan traditional X-ray film to acquire secondary capture (SC) images appears to be an acceptable solution. Unfortunately, there is no effective way of preventing the creation of fraudulent SC images. The implementation of medical SC images has to conform to security regulations, such as prevention of data modification and authentication of identity, by law. In this paper, we suggest a method, called software-embedded digital signature, to ensure the integrity and authentication of Digital Imaging and Communications in Medicine (DICOM) of SC image scanned from X-ray film and captured in digital form. During the scanning process, the image is converted into DICOM format and the digital signature was added. The scanning, converting and signing processes are locked with a scanner controller, digital signature module, and patient-identifiable data, and all of these are processed in the scanning system before saving the digital image onto a computer.