CV algorithm to detect image tampering

High quality digital images are very common due to easiness in imaging devices and
inexpensive storage. However, they are easy to manipulate because of the availability of the
powerful editing software and tools. Some software such as Photoshop, 3DS Max are so
sophisticated that it is very hard to distinguish tampered images from their authentic
counterparts. This raises questions regarding the authenticity of digital images, damages trust in
visual media and creates unacceptable digital evidences for real life applications such as criminal
investigation. An example of content tampering is shown in the figure below. You are asked to
propose a CV algorithm to detect image tampering. Design a conceptual/block diagram, provide
justifications for each step and the specific order and techniques you adopt in combining
different components. Try to provide as much information as needed, including details of your
algorithm (either in stepwise fashion or in algorithm style). For example, if you use sharpening
filters, specify the specific type of filter you will use. Also mention two shortcomings of your
approach, where your algorithm will not work.