Stalin would have loved Photoshop

M&C Science & Nature reported on how some scientific journals are implementing new security measures, including digital photo testing to prevent fraud by authors such as the recent alleged stem cell research fraud. 

Photo manipulation has been around for ages, from hand tinting daguerreotypes  to early examples of revisionist history by Stalin and even more recent events such as the Toppling of the Saddam statue which according to reports was a staged event and creatively cropped to make the crowd look bigger. 

There's a paper on Digital Forensics by A.C. Popescu and H. Farid which has some examples showing the magnitudes of Fourier transforms on images.  A Fourier transform is also a common algorithm that can be used in content-based image retrieval (CBIR) systems.  The SystemOne Retrievr application is a great example of a CBIR, though I'm uncertain of the algorithms used in that application.

Other articles and sites of interest:
Digital Image Integrity
Forensic Resources (has a Free 2D Fourier Transform Plug-in)