Security on Fragile and Semi-fragile Watermarks Authentication

Abstract

ABSTRACT Digital image manipulation software is now readily available on personal computers. It is therefore very simple to tamper with any image and make it available to others. Ensuring digital image security has therefore become a major issue. Watermarking has become a popular technique for copyright enforcement and image The aim of this paper is to present an overview of some possible attacks which may cause harm the present watermarking techniques. Here we have identified the attacks which frequently attacks some very well known fragile and semifragile watermarking techniques.. General Terms Security, Watermarking and Authentication. Keywords Attack, image authentication, watermark, fragile, semi-fragile, security, private key, public key. attack threats. We have specially fo 1. INTRODUCTION In today's world, digital images and video are gradually replacing their classical analog counterparts. This is quite understandable because digital format is easy to edit, modify, and exploit. Digital images and videos can be readily shared via computer networks and conveniently processed for queries in databases. Also, digital storage does not age or degrade with usage. On the other hand, thanks to powerful editing programs, it is very easy even for an amateur to maliciously modify digital media and create perfect forgeries. It is usually much more complicated to tamper with analog tapes and images. Tools that help us establish the authenticity and integrity of digital media are thus essential and can prove vital whenever questions are raised about the origin of an image and its content. In the past few years, many new techniques and concepts based on data hiding or steganography have been introduced as a means for tamper detection in digital images and for image Fragile watermarks are designed to detect every possible change in pixel values. In many schemes, it can be shown that without the secret key, the probability of a modification that will not be detected can be related to a cryptographic element present in the scheme, such as a hash function. Semi-fragile watermarks are moderately robust and thus provide a softer evaluation criterion (authentication with a degree). Some schemes have been specifically designed to be compatible with certain distortion, such as JPEG or wavelet compression. There is another special group of authentication techniques that can be termed authentication. In those schemes, robustly extracted image features are embedded in the image in a semi-robust manner to help identify gross changes in the image. In the security domain, an integrity service is unambiguously defined as one, which ensures that the sent and received data are identical. This binary definition is also applicable to images. In real life situations, images can be transformed, their pixel values can be modified but not the actual meaning of the image. In order to provide an authentication service for still images, it is important to distinguish between malicious manipulations, which consist of changing the content of the original image and manipulations related to the use of images. In this paper, we focus on different attacks on different watermarking techniques. So many watermarking schemes have been designed to provide authenticity to the digital images. But many of the proposed ideas are not totally secure because of the cused on the identification of the attacks to which the proposed watermarking schemes are vulnerable..