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.