Being in law enforcement, I recently attended a seminar - 'Forensic Digital Photography'
A statement made by a presenter: "Digital photography is MORE secure than film." This from a man who is an expert in determining if a photo is original or not. The main item is noise. Each camera produces noise (which is unique to that camera) and it is evenly spread on the picture. Any modifications change the noise pattern in that area and allows them to detect alterations.
Where as with film, it is easy to change a photo, photograph that photo
and have an original negative that is very difficult to determine if it
had been altered. Altering photos has been with us since the beginning,
it's just that digital makes it much easier for the lay person.