15-05-2013, 04:09 PM
Digital watermarking
Digital watermarking.doc (Size: 1,006.5 KB / Downloads: 19)
INTRODUCTION
The use of digital multimedia technology in a wide range of daily applications has been expanding continuously for the last two decades, because digital data has many advantages over analog data. Reliable and efficient storage, ease of transmission, sophisticated manipulation techniques, efficient distribution are some of its main advantages. The main focus of this thesis is digital audio data security and secret communication over audio objects. There has been much interest in using digital multimedia, such as images, audio, video, for the purpose of data hiding because of its inherent redundancy, perceptual properties and its inflating enlargement. Information hiding in digital audio can be used for such diverse applications as proof of ownership, access control authentication, integrity check, secret communication, fingerprinting, broadcast monitoring and event annotation. There are two well-known special cases of information hiding – digital watermarking and stegnography.
In the watermarking context, some copyright or copy control information is embedded into the cover host audio signals in order to prove the ownership of the cover object or preserve unauthorized copying of it. In addition to this, the watermarking can also be used for various other applications mentioned above. Detection of the hidden information by untrusted parties and reliable and or correct watermark extraction are two major problem areas in watermarking. Spread spectrum watermarking has been proposed as a solution to the latter problem. In spread spectrum watermarking, the embedded message is spread over very many samples or frequency bins so that the energy in one sample or bin is very small.
What is Watermarking ?
A digital watermark is a digital signal or pattern inserted into a digital image. Since this signal or pattern is present in each unaltered copy of the original image, the digital watermark may also serve as a digital signature for the copies. A given watermark may be unique to each copy (e.g. to identify the intended recipient), or be common to multiple copies (e.g. to identify the document source). In either case, the watermarking of the document involves the transformation of the original into another form. This distinguishes digital watermarking from digital fingerprinting, where the original file remains intact and a new created file 'describes' the original file's content.
Elements of a Watermarking System: -
A watermarking system can be viewed as a communication system consisting of three main elements: an embedder, a communication channel and a detector. Watermark information is embedded into the signal itself, instead of being placed in the header of a file or using encryption like in other security techniques, in such a way that it is extractable by the detector. To be more specific, the watermark information is embedded within the host signal before the watermarked signal is transmitted over the communication channel, so that the watermark can be detected at the receiving end, that is, at the detector. A general watermarking system is illustrated in Fig. 1. The dotted lines represent the optional components, which may or may not be required according to the application. First of all, a watermark Wo is generated by the watermark generator possibly with a secret watermark generation key Kg. The watermark Wo can be a logo, or be a pseudo-random signal.
Watermarking Requirements :-
In this section,studying a number of watermarking system requirements as well as the tradeoffs among them.
• Security: The security requirement of a watermarking system can differ slightly depending on the application. Watermarking security implies that the watermark should be difficult to remove or alter without damaging the host signal. As all watermarking systems seek to protect watermark information, without loss of generality, watermarking security can be regarded as the ability to assure secrecy and integrity of the watermark information, and resist malicious attacks
Digital Watermarking – Framework:
Watermarking is the process that embeds data called watermark into a media such that watermark can be detected or extracted later to make an assertion about the media. For example, a very simple yet widely used digital watermarking technique would be – for images – to add a visible seal on top of an existing image. Figure illustrates the basic principle behind watermarking. Watermarking is viewed as a process of combining two pieces of information in such a way that they can be independently detected by two very different detection processes. One piece of information is the media data So, which will be viewed (detected) by a human observer. The other piece of information is a watermark, which will be detected by a specially designed watermark detector. The first step is to encode the watermark into a form that will be easily inserted with the media. The watermark inserter then combines the encoded representation of the watermark with the document. If the watermarking insertion process is design correctly, the result is media that appears identical to the original when perceived by a human, but which yields the encoded watermark information when processes by a watermark detector.
Digital Watermarking – Examples:-
This section presents digital watermarking methods for text images and video. These medium differ in ways that present unique problems for watermarking. Still the principle of watermarking remains the same [figure].
Image: Watermarks for natural images typically modify pixel intensities or transform coefficients, although it is conceivable that a watermark could alter other features such as edges or textures. An image may be subject to a great deal of manipulation such as filtering, cropping, geometric transformations, compression and compositing with other images and hostile attacks. Thus imperceptibility, robustness are usually the most important properties of image watermarks. Also since many images are compressed (JPEG, GIF) watermarking algorithms that operate in the transform or wavelet domain may be useful. One potential difficulty in image watermarking is the finite bandwidth available. As the image size decreases, the permissible message length decreases.
Software Implementation
In this the user is required to perform the following implementation:
i. Objects browsing such as Image, Audio, Video .
ii. Select particular object and encrypt it.
iii. Browsing source file and add secret key & save results as destination.
iv. Finally hide message in object.
v. Then unhide that message using decryption technique, it opposite to encryption.
This thesis has two main interests, one is digital multimedia security and the other is robust audio hashing. The audio hashing problem can be considered both as a database search and retrieval problem and a multimedia security problem, in that the expected signature can be instrumental in watermarking. More explicitly, the signature obtained by robust hashing could be used as part of watermarking scheme security. It is known that one of the general requirements of data hiding is security. Security does not only mean to be unbroken. Detection of the presence of the hidden data some times might be a weak point of the system, especially in steganographic techniques. Some statistical tests in order to detect the very presence of the hidden information have been developed for image security. However there is no such general method for audio in literature. In this thesis one of our goals is to design an automatic detection system, which detects the very presence of hidden information in audio signals. Although the stegoobjects, in principle perceptually very similar to cover objects, they are not identical and that they may contain some telltale effects, some extra information in it. Thus they have distinct statistics. Our approach has been to exploit those statistical differences in order to develop a hidden message detector. That intend to design a universal detector that should function irrespective of the specific algorithm used for embedding, of the embedding strength and of the message size. One way to sense the artifacts caused in the cover message by data hiding is to use objective audio quality.
System Architecture:-
Watermarking is the process that embeds data called watermark into a media such that watermark can be detected or extracted later to make an assertion about the media. For example, a very simple yet widely used digital watermarking technique would be – for images – to add a visible seal on top of an existing image. Encryption is the process of transforming the information Generic to insure its security. With the huge growth of computer networks and the latest advances in digital technologies, a huge amount of digital data is being exchanged over various types of networks. It is often true that a large part of this information is either confidential or private. As a result, different security techniques have been used to provide the required protection. The security of digital images has become more and more important due to the rapid evolution of the Internet in the digital world today. The security of digital images has attracted more attention recently, and many different image encryption methods have been proposed to enhance the security of these images Image encryption techniques try to convert an image to another one that is hard to understand. On the other hand, image decryption retrieves the original image from the encrypted one.
Description
In addition to digital watermarking, the general idea of hiding some information in digital Content has a wider class of applications that go beyond mere copyright protection and authentication. The techniques involved in such applications are collectively referred to as information hiding. For example, an image printed on a document could be annotated by information that could lead an user to its high resolution version. Metadata provides additional information about an image. Although metadata can also be stored in the file header of a digital image, this approach has many limitations. Usually, when a file is transformed to another format (e.g., from TIFF to JPEG or to bmp), the metadata is lost. Similarly, cropping or any other form of image manipulation destroys the metadata. Finally, the metadata can only be attached to an image as long as the image exists in the digital form and is lost once the image is printed.
Conclusions:
Watermarking is the process that embeds data called watermark into a media such that watermark can be detected or extracted later to make an assertion about the media. For example, a very simple yet widely used digital watermarking technique would be – for images – to add a visible seal on top of an existing image Digital watermarking is a rapidly evolving area of research and development. Only discuss the key problems in this area and presented some known solutions in this chapter. One key research problem that still face today is the development secure watermarking technique for different digital media including images, video and audio. The solution to these problem will require application of known results and development of new results in the fields of information and coding theory, adaptive signal processing, game theory, statistical decision theory, and cryptography.
Digital watermarking.doc (Size: 1,006.5 KB / Downloads: 19)
INTRODUCTION
The use of digital multimedia technology in a wide range of daily applications has been expanding continuously for the last two decades, because digital data has many advantages over analog data. Reliable and efficient storage, ease of transmission, sophisticated manipulation techniques, efficient distribution are some of its main advantages. The main focus of this thesis is digital audio data security and secret communication over audio objects. There has been much interest in using digital multimedia, such as images, audio, video, for the purpose of data hiding because of its inherent redundancy, perceptual properties and its inflating enlargement. Information hiding in digital audio can be used for such diverse applications as proof of ownership, access control authentication, integrity check, secret communication, fingerprinting, broadcast monitoring and event annotation. There are two well-known special cases of information hiding – digital watermarking and stegnography.
In the watermarking context, some copyright or copy control information is embedded into the cover host audio signals in order to prove the ownership of the cover object or preserve unauthorized copying of it. In addition to this, the watermarking can also be used for various other applications mentioned above. Detection of the hidden information by untrusted parties and reliable and or correct watermark extraction are two major problem areas in watermarking. Spread spectrum watermarking has been proposed as a solution to the latter problem. In spread spectrum watermarking, the embedded message is spread over very many samples or frequency bins so that the energy in one sample or bin is very small.
What is Watermarking ?
A digital watermark is a digital signal or pattern inserted into a digital image. Since this signal or pattern is present in each unaltered copy of the original image, the digital watermark may also serve as a digital signature for the copies. A given watermark may be unique to each copy (e.g. to identify the intended recipient), or be common to multiple copies (e.g. to identify the document source). In either case, the watermarking of the document involves the transformation of the original into another form. This distinguishes digital watermarking from digital fingerprinting, where the original file remains intact and a new created file 'describes' the original file's content.
Elements of a Watermarking System: -
A watermarking system can be viewed as a communication system consisting of three main elements: an embedder, a communication channel and a detector. Watermark information is embedded into the signal itself, instead of being placed in the header of a file or using encryption like in other security techniques, in such a way that it is extractable by the detector. To be more specific, the watermark information is embedded within the host signal before the watermarked signal is transmitted over the communication channel, so that the watermark can be detected at the receiving end, that is, at the detector. A general watermarking system is illustrated in Fig. 1. The dotted lines represent the optional components, which may or may not be required according to the application. First of all, a watermark Wo is generated by the watermark generator possibly with a secret watermark generation key Kg. The watermark Wo can be a logo, or be a pseudo-random signal.
Watermarking Requirements :-
In this section,studying a number of watermarking system requirements as well as the tradeoffs among them.
• Security: The security requirement of a watermarking system can differ slightly depending on the application. Watermarking security implies that the watermark should be difficult to remove or alter without damaging the host signal. As all watermarking systems seek to protect watermark information, without loss of generality, watermarking security can be regarded as the ability to assure secrecy and integrity of the watermark information, and resist malicious attacks
Digital Watermarking – Framework:
Watermarking is the process that embeds data called watermark into a media such that watermark can be detected or extracted later to make an assertion about the media. For example, a very simple yet widely used digital watermarking technique would be – for images – to add a visible seal on top of an existing image. Figure illustrates the basic principle behind watermarking. Watermarking is viewed as a process of combining two pieces of information in such a way that they can be independently detected by two very different detection processes. One piece of information is the media data So, which will be viewed (detected) by a human observer. The other piece of information is a watermark, which will be detected by a specially designed watermark detector. The first step is to encode the watermark into a form that will be easily inserted with the media. The watermark inserter then combines the encoded representation of the watermark with the document. If the watermarking insertion process is design correctly, the result is media that appears identical to the original when perceived by a human, but which yields the encoded watermark information when processes by a watermark detector.
Digital Watermarking – Examples:-
This section presents digital watermarking methods for text images and video. These medium differ in ways that present unique problems for watermarking. Still the principle of watermarking remains the same [figure].
Image: Watermarks for natural images typically modify pixel intensities or transform coefficients, although it is conceivable that a watermark could alter other features such as edges or textures. An image may be subject to a great deal of manipulation such as filtering, cropping, geometric transformations, compression and compositing with other images and hostile attacks. Thus imperceptibility, robustness are usually the most important properties of image watermarks. Also since many images are compressed (JPEG, GIF) watermarking algorithms that operate in the transform or wavelet domain may be useful. One potential difficulty in image watermarking is the finite bandwidth available. As the image size decreases, the permissible message length decreases.
Software Implementation
In this the user is required to perform the following implementation:
i. Objects browsing such as Image, Audio, Video .
ii. Select particular object and encrypt it.
iii. Browsing source file and add secret key & save results as destination.
iv. Finally hide message in object.
v. Then unhide that message using decryption technique, it opposite to encryption.
This thesis has two main interests, one is digital multimedia security and the other is robust audio hashing. The audio hashing problem can be considered both as a database search and retrieval problem and a multimedia security problem, in that the expected signature can be instrumental in watermarking. More explicitly, the signature obtained by robust hashing could be used as part of watermarking scheme security. It is known that one of the general requirements of data hiding is security. Security does not only mean to be unbroken. Detection of the presence of the hidden data some times might be a weak point of the system, especially in steganographic techniques. Some statistical tests in order to detect the very presence of the hidden information have been developed for image security. However there is no such general method for audio in literature. In this thesis one of our goals is to design an automatic detection system, which detects the very presence of hidden information in audio signals. Although the stegoobjects, in principle perceptually very similar to cover objects, they are not identical and that they may contain some telltale effects, some extra information in it. Thus they have distinct statistics. Our approach has been to exploit those statistical differences in order to develop a hidden message detector. That intend to design a universal detector that should function irrespective of the specific algorithm used for embedding, of the embedding strength and of the message size. One way to sense the artifacts caused in the cover message by data hiding is to use objective audio quality.
System Architecture:-
Watermarking is the process that embeds data called watermark into a media such that watermark can be detected or extracted later to make an assertion about the media. For example, a very simple yet widely used digital watermarking technique would be – for images – to add a visible seal on top of an existing image. Encryption is the process of transforming the information Generic to insure its security. With the huge growth of computer networks and the latest advances in digital technologies, a huge amount of digital data is being exchanged over various types of networks. It is often true that a large part of this information is either confidential or private. As a result, different security techniques have been used to provide the required protection. The security of digital images has become more and more important due to the rapid evolution of the Internet in the digital world today. The security of digital images has attracted more attention recently, and many different image encryption methods have been proposed to enhance the security of these images Image encryption techniques try to convert an image to another one that is hard to understand. On the other hand, image decryption retrieves the original image from the encrypted one.
Description
In addition to digital watermarking, the general idea of hiding some information in digital Content has a wider class of applications that go beyond mere copyright protection and authentication. The techniques involved in such applications are collectively referred to as information hiding. For example, an image printed on a document could be annotated by information that could lead an user to its high resolution version. Metadata provides additional information about an image. Although metadata can also be stored in the file header of a digital image, this approach has many limitations. Usually, when a file is transformed to another format (e.g., from TIFF to JPEG or to bmp), the metadata is lost. Similarly, cropping or any other form of image manipulation destroys the metadata. Finally, the metadata can only be attached to an image as long as the image exists in the digital form and is lost once the image is printed.
Conclusions:
Watermarking is the process that embeds data called watermark into a media such that watermark can be detected or extracted later to make an assertion about the media. For example, a very simple yet widely used digital watermarking technique would be – for images – to add a visible seal on top of an existing image Digital watermarking is a rapidly evolving area of research and development. Only discuss the key problems in this area and presented some known solutions in this chapter. One key research problem that still face today is the development secure watermarking technique for different digital media including images, video and audio. The solution to these problem will require application of known results and development of new results in the fields of information and coding theory, adaptive signal processing, game theory, statistical decision theory, and cryptography.