Abstract
These days, for the copyright protection and security of multimedia data in this age of the tech-savvy world, watermarking is a very important technique. Moreover, with the inclusion of biometrics for the watermarking schemes, the concept of “something you are” is included in the watermark and/or cover image. This thereby increases the security intensity in the multimedia data. And to give a glimpse of the technique the concepts of Watermarking, biometric and watermarking using biometrics is discussed. Finally, a particular case of real time watermarking of data using biometric is discussed by specifying a practical example.
TopIntroduction
The practice of hiding a message about an image, audio clip, video clip, or other work of multimedia within that work itself is called watermarking. It is mainly of two basic types; visible and invisible. Visible ones are commonly available in currency notes, stamp papers, etc. The invisible or the imperceptible variant is the one that will be discussed here. Alternately, watermarking can be considered as the practice of imperceptibly altering a work to embed a message about that work. Watermarking has been practiced and has existed for quite long, at least several centuries, if not the millennia—the field of digital watermarking only gained widespread popularity as a research topic in the latter half of the 1990s as per the earlier books that have devoted substantial space to the subject of digital watermarking. However, here in this chapter the watermarking involves a special data type which is related to us the biological beings as our individualistic traits, either characteristic wise or behavioral, i.e., the biometric.
Watermarking, information hiding and steganography are the three fields that have a great deal of overlapping but there are fundamental philosophical differences affecting the requirements. Information or data hiding encompasses a wide range of problems beyond that of embedding messages in content, referring to make the information imperceptible or keeping the existence of the information secret or even maintaining anonymity while using a network and keeping part of a database secret from unauthorized users unlike watermarking. Steganography is derived from the Greek words “steganos” and “graphia,” which mean “covered,” and “writing.” It thus indicates the art of concealed communication where the very existence of a message is secret. Thereby these three techniques are not to be confused among each other.
Other than embedding of watermark in image and video formats of multimedia, watermarking has been done on the speech and audio signals as well. The audio signal watermarking is normally done with the pre-requisite that it does not degrade the audibility of the signal. Some of the popular audio watermarking methods are least significant bit (LSB) coding, echo hiding scheme and spread spectrum watermarking.
The word “biometrics” comes from the Greek words bio (life). It may be a characteristic which is a measurable biological and behavioral characteristic that can be used for automated recognition or a process that encompasses automated methods of recognizing an individual based on some measurable biological and behavioral characteristic. Biometric identification is generally preferred over traditional methods (e.g. passwords, smart-cards) because its information is virtually impossible to steal as it is “something you are.” A number of biometric characteristics are being used in various applications as Universality, Uniqueness, Measurability, Performance, Acceptability, and Circumvention. When we say watermarking of biometric data, it may be in either way. That is, it might be a biometric image template being watermarked for its authenticity or a host/carrier image being watermarked by the user’s or author’s biometric for copyright issues. We hereby discuss a few different techniques of either type that have been employed concerning a few established works.
Rao (2009) have discussed a method for copyright protection of digital images by watermarking the images with the fingerprint features of the author/owner. Here the minutiae points were extracted from the fingerprint, and their coordinates are represented as a matrix to utilize them as the watermark. The transform domain used is a hybrid form of the discrete cosine transform and the singular value decomposition. This type of watermarking is done mainly to solve cases of any ownership dispute on the image. This is done by extracting the coordinates of the minutiae points from the watermarked image and compared with those extracted from the fingerprint of the person claiming the ownership. Thereby the biometric feature is utilized along with the watermarking scheme to ascertain that the digital image information is authenticated and secure.
Key Terms in this Chapter
Visual Secret Sharing: Visual Secret Sharing (VSS) is a sub class of Secret Sharing (SS) scheme of 1970s, called (??,??) threshold schemes, to encode a secret into ?? pieces (“shadows” or “shares”) so that the pieces can be distributed to ?? participants at different locations. The secret can only be reconstructed from ?? or more pieces (?? = ??)). Since Shamir's scheme is a basic secret sharing scheme and is easy to implement, it is commonly used in many applications. However, the computation complexity of different schemes are different, varying from ?? (??log 2 ??) for the polynomial evaluation and interpolation in deterministic, while it may be (??, ??)-secret sharing scheme for grayscale images. So in general it is something like a secret picture to be shared among n number of participants. The picture is divided into n transparencies (shares) such that if any k transparencies are placed together, the picture becomes visible, but if fewer than m transparencies are placed together, nothing can be seen. Such a scheme is constructed by viewing the secret picture as a set of black and white pixels and handling each pixel separately. The schemes are perfectly secure and easily implemented without any cryptographic computation. Because a secret kept in a single scheme could be easily lost or damaged or even been detected, and later replaced to give wrong information at receiver end as well. Thus multiple schemes may be preferred. A further improvement allows each transparency (share) to be an innocent picture (e.g. a picture of a landscape or a picture of a building), thus concealing the fact that secret sharing is taking place.
Multimedia Data: Different, basic data types: text, images, audio, video, etc., are typically the elements for the building blocks of the generalized multimedia environments, platforms, or integrating tools. They comprise of ASCII based text data, typically stored in processor files, spreadsheets, databases and annotations on more general multimedia objects. With availability and proliferation of GUIs, text fonts the job of storing text is becoming complex allowing special effects (color, shades, etc.). For image or picture data, there is great variance in the quality and size of storage for still images. Digitalized images are sequence of pixels that represents a region in the user's graphical display. The space overhead for still images varies on the basis of resolution, size, complexity, and compression scheme used to store image. The popular image formats are jpg, png, bmp, tiff. An increasingly popular datatype being integrated in most of applications is audio as it is quite space intensive. One minute of sound can take up to 2-3 Mbs of space. Several techniques are used to compress it in suitable format. One on the most space consuming multimedia data type is digitalized video. The digitalized videos are stored as sequence of frames. Depending upon its resolution and size a single frame can consume upto 1 MB. Also to have realistic video playback, the transmission, compression, and decompression of digitalized require continuous transfer rate. These days, in the age of 3D movies we have graphic objects a data type as well. This consists of special data structures used to define 2D and 3D shapes through which we can define multimedia objects. These include various formats used by image, video editing applications. Examples are CAD / CAM objects.
Cryptography: Cryptography is the practice and study of techniques for secure communication in the presence of third parties or adversaries. So it is nothing but the art of protecting information by transforming it (encrypting it) into an unreadable format, called cipher text. Thus it is in general an idea of constructing and analyzing protocols that overcome the influence of adversaries and which are related to various aspects in information security such as data confidentiality, data integrity, and authentication. A person who possesses the secret key, which can be even his biometric information, can decrypt/decipher the message to readable/understandable format. Encrypted messages can sometimes be broken by cryptanalysis, also called codebreaking, although modern cryptography techniques are virtually unbreakable or rather claim to be so till some hacker breaks into it. Cryptography systems can be broadly classified into symmetric-key systems that use a single key that both the sender and recipient have, and public-key systems that use two keys, a public key known to everyone and a private key that only the recipient of messages uses. Modern cryptography intersects the disciplines of mathematics, computer science, and electrical engineering. Applications of cryptography include ATM cards, computer passwords, and electronic commerce.
Watermarking: The process of embedding information/data of any type into another digital signal(audio/video/text/image), to verify its authenticity or owner identification. It is similar to paper/currency notes bearing visible watermarks for visual authentication and identification. A signal may carry several different watermarks at the same time. It may be visible (where watermark is visible in the picture/video) or invisible (not visible to naked eye but can be extracted digitally).
Transform: Change of data from one domain to another is called transform. The most popular variants of transform normally transform a particular signal from time domain to frequency domain or vice versa. The signal in discussion may be of any form, i.e., speech, audio, image, video, etc. Fourier Transform is one of the most popular transform that converts a time domain signal to frequency domain and its inverse transform works the other way round converting frequency to time. Other than this there are many more such transforms starting from wavelt transform, Z-transform, Laplace transform, Wavelet transform,etc.
Real Time Systems: Real-time systems are those systems that must deliver services in a timely manner. It may not mean to be necessarily fast, but must meet some timing deadline. The deadline may be varying application to application. In general an embedded system is hidden from view within a larger system, rather many real-time and embedded systems exist, often without the awareness of their users (Washing machine, photocopier, mobile phone, car, aircraft, industrial plant, microwave oven, toothbrush, CD player, medical devices, etc.). Moreover their validation for correctness is very important, mainly for those embedded real-time systems that are safety critical, i.e., if they do not complete on a timely basis, serious consequences result. Bugs in embedded real-time systems are often difficult or expensive to fix, so before deployment proper testing is a must.
Steganography: Watermarks may be for wide spread use. But a modification for that is steganography, where the transmitting end communicates a secret message embedded in the digital signal to the receiver. The main objective is to add owner descriptive information or any other form of authenticating information to the signal concerned, such that is difficult to remove. Moreover, to covert communication between individuals, some hidden embedded information could be used as well.
Biometrics: As per information technology, biometrics refers to technologies that measures and analyzes biological characteristics, such as DNA, fingerprints, eye retinas and irises, voice patterns, facial patterns and hand measurements, for authentication purposes. Authentication by biometric verification is becoming increasingly common in corporate and public security systems, consumer electronics and point of sale (POS) applications. In addition to security, the driving force behind biometric verification has been convenience. They are mainly good at preventing identity theft, by encryption of one’s biometric data somewhere to authenticate the legitimate user.