Comprehensive image index and detection of tampering in a digital image

Integrity of digital image is of prime importance in areas relating to police investigation, evidence in the court, medical science and biometric images. With easy availability of image editing software and large volume of digital images in daily life, detection of image tampering has become a serious challenge for image processing community. Image content based hash function for authenticating an image is being widely used. In this paper we define Comprehensive Image Index that tells about the type of tampering done in a digital image. Most of the existing hashing technique extract one feature of the image and develop a single index hash function for image tampering detection. Proposed technique uses a new 3-tupled comprehensive image index which incorporates indices corresponding to structural tampering, brightness level adjustment and contrast manipulation. This technique is found to be robust against content preserving manipulations at the same time it is sensitive to malicious tampering.