IMAGE AUTHENTICATION TECHNIQUES seminars report

[seminar surveyer]

Prepared by:
C.Alekhya
Computer Science Engineering, J.N.T.University
SVPCET,RVS Nagar puttur

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Abstract

Automatic video surveillance (AVS) systems are used for continuous and effective monitoring of dangerous and remote sites. Video data acquired by the automatic video surveillance system can be recorded and presented as a proof in front of court law. But digital video data lacks legal validity due to the ease to manipulate them without leaving any trace of modification. Image authentication is the process of giving a legal validity to the video data. By authentication technique content tampering can be detected and we can indicate the true origin of the data.

INTRODUCTION

This paper explores the various techniques used to authenticate the visual data recorded by the automatic video surveillance system. Automatic video surveillance systems are used for continuous and effective monitoring and reliable control of remote and dangerous sites. Some practical issues must be taken in to account, in order to take full advantage of the potentiality of VS system. The validity of visual data acquired, processed and possibly stored by the VS system, as a proof in front of a court of law is one of such issues. But visual data can be modified using sophisticated processing tools without leaving any visible trace of the modification. So digital or image data have no value as legal proof, since doubt would always

A. AUTOMATIC VISUAL SURVEILLANCE SYSTEM
Automatic Visual Surveillance system is a self monitoring system which consists of a video camera unit, central unit and transmission networks
A pool of digital cameras is in charge of frame the scene of interest and sent corresponding video sequence to central unit. The central unit is in charge of analyzing the sequence and generating an alarm whenever a suspicious situation is detected. Central unit also transmits the video sequences to an intervention centre such as security service provider, the police department or a security guard unit. Somewhere in the system the video sequence or some part of it may be stored and when needed the stored sequence can be used as a proof in front of court of law. If the stored digital video sequences have to be legally credible, some means must be envisaged to detect content tampering and reliably trace back to the data origin .

B.AUTHENTICATION TECHNIQUES:
Authentication techniques are performed on visual data to indicate that the data is not a forgery; they should not damage visual quality of the video data. At the same time, these techniques must indicate the malicious modifications include removal or insertion of certain frames, change of faces of individual, time and background etc. Only a properly authenticated video data has got the value as legal proof. There are two major techniques for authenticating video data. They are as follows

1.Cryptographic Data Authentication
It is a straight forward way to provide video authentication, namely through the joint use of asymmetric key encryption and the digital Hash function. Cameras calculate a digital summary (digest) of the video by means of hash function. Then they encrypt the digest with their private key, thus obtaining a signed digest which is transmitted to the central unit together with acquired sequences. This digest is used to prove data integrity or to trace back to their origin. Signed digest can only read by using public key of the camera.

2.Watermarking- based authentication
Watermarking data authentication is the modern approach to authenticate visual data by imperceptibly embedding a digital watermark signal on the data. Digital watermarking is the art and science of embedding copyright information in the original files. The information embedded is called ‘watermarks ‘. Digital watermarks are difficult to remove without noticeably degrading the content and are a covert means in situation where copyright fails to provide robustness. In recent years, the distribution of works of art, including pictures, music, video and textual documents, has become easier. With the widespread and increasing use of the Internet, digital forms of these media (still images, audio, video, text) are easily accessible. This is clearly advantageous, in that it is easier to market and sell one's works of art. However, this same property threatens copyright protection. Digital documents are easy to copy and distribute, allowing for pirating. There are a number of methods for protecting ownership. One of these is known as digital watermarking.
Digital watermarking is the process of inserting a digital signal or pattern (indicative of the owner of the content) into digital content. The signal, known as a watermark, can be used later to identify the owner of the work, to authenticate the content, and to trace illegal copies of the work. Watermarks of varying degrees of obtrusiveness are added to presentation media as a guarantee of authenticity, quality, ownership, andsource. To be effective in its purpose, a watermark should adhere to a few requirements. In particular, it should be robust, and transparent. Robustness requires that it be able to survive any alterations or distortions that the watermarked content may undergo, including intentional attacks to remove the watermark, and common signal processing alterations used to make the data more efficient to store and transmit. This is so that afterwards, the owner can still be identified. Transparency requires a watermark to be imperceptible so that it does not affect the quality of the content, and makes detection, and therefore removal, by pirates less possible.The media of focus in this paper is the still image. There are a variety of image watermarking techniques, falling into 2 main categories, depending on in which domain the watermark is constructed: the spatial domain (producing spatial watermarks) and the frequency domain (producing spectral watermarks). The effectiveness of a watermark is improved when the technique exploits known properties of the human visual system. These are known as perceptually based watermarking techniques. Within this category, the class of image-adaptive watermarks proves most effective.In conclusion, image watermarking techniques that take advantage of properties of the human visual system, and the characteristics of the image create the most robust and transparentwatermarks.