  Photographs are considered to be the most powerful and trustworthy media of
expression. For a long time, those were accepted as proves of evidences in
varied fields such as journalism, forensic investigations, military
intelligence, scientific research and publications, crime detection and legal
proceedings, investigation of insurance claims, medical imaging etc. Today,
digital images have completely replaced the conventional photographs from every
sphere of life but unfortunately, they seldom enjoy the credibility of their
conventional counterparts, thanks to the rapid advancements in the field of
digital image processing. The increasing availability of low cost and sometimes
free of cost image editing software such as Photoshop, Corel Paint Shop,
Photoscape, PhotoPlus, GIMP and Pixelmator have made the tampering of digital
images even more easier and a common practice. Now it has become quite
impossible to say whether a photograph is a genuine camera output or a
manipulated version of it just by looking at it. As a result, photographs have
almost lost their reliability and place as proves of evidences in all fields.
This is why digital image tamper detection has emerged as an important research
area to establish the authenticity of digital photographs by separating the
tampered lots from the original ones. This paper gives a brief history of image
tampering and a state-of-the-art review of the tamper detection techniques.
