Digital Image Forensics: Progress and Challenges Ms. Neha Singh 1 , Dr. Sandeep Joshi 2 1Ph.D. Scholar, 2Associate Professor, Department of CSE, Manipal University Jaipur, India Abstract: The growth of sophisticated image processing and editing software has made the manipulation of digital images easy and imperceptible to the naked eyes. This has increased the demand to assess the trustworthiness of digital images when used in crime investigation, as evidence in court of law and for surveillance purposes. This paper presents a comprehensive investigation of the progress and challenges in the field of digital image forensics to help the beginners in developing the understanding, apprehending the requirements and identifying the research gaps in this domain. Keywords: Digital image forensics, forgery, image authentication, tampering detection, passive forensics, anti-forensics. 1. INTRODUCTION The development and ease of availability of image processing software and image capturing devices together with the ease of accessibility of the Internet has increased the ambivalence in the authenticity of the digital images [1-5]. Uses of digital images as evidence for decision making or judgments and as support for a scientific argument are examples where not only ownership of the images is required to be established, but it is equally important to establish their authenticity. Digital image watermarking and digital signatures have been used as active methods to restore the lost trust in digital images [3]. These approaches embed some self-authenticating information in the digital media with the objective of assessing the authenticity and integrity of the digital images. Digital image watermarking belongs to the class of active approach [1-3] for image forensics as it requires the knowledge of the authentication code and the method used to embed it into the image. The hidden information is generally imperceptible and robust against most of the intended and unintended attacks like histogram equalization, compression, rotation, cropping, resampling, filtering, addition of noise etc. But, a major disadvantage of active techniques is that they require manipulation of the original image either during capturing or during storage. Moreover, the need of generating the digital signature or watermark before saving the images calls for specially equipped image capturing devices. Thus, the use of digital signatures and watermarking as image forensic tools is not widely adopted [3]. Instead, passive digital image forensics [1-3] has been looked upon as the solution with the primary objective of validating the authenticity of the digital images by either detecting tampering or recovering information about their history. The passive authenticating methods are blind as these do not require the knowledge of the original image, but are based on the fact that most of the image capturing devices and image processing operations introduce distinct traces within the image generally referred to as the fingerprints [4, 5]. Passive digital image forensic methods study underlying fingerprints with respect to the two major working domains [3]. The first domain pertains to source authentication where the purpose is to identify the device used for capturing the image and reconstruct its generation process. The second realm of digital image forensics is concerned with the detection of tampering to establish if the image has been manipulated and possibly identify the processes involved. Counterfeiting a digital image without leaving any perceptible traces is not so difficult now with the advanced and user friendly image processing and image editing software. Fig. (1) depicts the generic active and passive image forensic methods. Fig. (1). Generic active and passive image forensic methods This paper presents a compendious study about the progress and challenges in the field of digital image forensics and is organized as follows: Section 2 elucidates the formation of images using a digital camera to understand the life cycle of a digital image. Section 3 offers a representation of the research aiming to identify and authenticate the device used to acquire a given digital image. Section 4 presents the major exploited prospect of research in digital image forensics domain that is, tampering detection. Section 5 sheds light on the countermeasures for digital image forensics. Finally section 6 concludes this paper and attempts to identify major challenges in this area.