How can I tell if someone modified the EXIF data in a photograph?

Question

Is it possible to detect if someone modified the EXIF data in a photograph? How would someone detect that the EXIF data has been modified?

Answer 1

See Can digital cameras sign images to prove authenticity? (from http://photo.stackexchange.com) for an post about this.

There is a way to "sign" them, but as far as I know, this does (a) not work with every camera and (b) requires additional hardware like Canons Original data security kit