digital watermarking

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A digital watermark is a kind of marker covertly embedded in a noise-tolerant
signal In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio signal processing, sound, image processing, images, and scientific measurements. Sig ...
such as audio, video or image data. It is typically used to identify ownership of the copyright of such signal. "Watermarking" is the process of hiding digital information in a
carrier signal In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform (usually sinusoidal) that is Modulation, modulated (modified) with an information-bearing signal (electrical engineering), signal for the purpose of conveying i ...
; the hidden information should,Ingemar J. Cox: ''Digital watermarking and steganography''. Morgan Kaufmann, Burlington, MA, USA, 2008 but does not need to, contain a relation to the carrier signal. Digital watermarks may be used to verify the authenticity or integrity of the carrier signal or to show the identity of its owners. It is prominently used for tracing
copyright infringement Copyright infringement (at times referred to as piracy) is the use of works Works may refer to: People * Caddy Works Pierce "Caddy" Works (January 2, 1896 – July 19, 1982) was an American basketball and baseball coach. He was the head b ...
s and for
banknote A banknote (often known as a bill (in the US and Canada), paper money, or simply a note) is a type of negotiable promissory note A promissory note, sometimes referred to as a note payable, is a legal instrument ''Legal instrument'' is a ...
authentication. Like traditional physical watermarks, digital watermarks are often only perceptible under certain conditions, e.g. after using some algorithm.Frank Y. Shih: ''Digital watermarking and steganography: fundamentals and techniques''. Taylor & Francis, Boca Raton, FL, USA, 2008 If a digital watermark distorts the carrier signal in a way that it becomes easily perceivable, it may be considered less effective depending on its purpose. Traditional watermarks may be applied to visible media (like images or video), whereas in digital watermarking, the signal may be audio, pictures, video, texts or 3D models. A signal may carry several different watermarks at the same time. Unlike
metadata Metadata is "data Data (; ) are individual facts, statistics, or items of information, often numeric. In a more technical sense, data are a set of values of qualitative property, qualitative or quantity, quantitative variable (research), v ...
that is added to the carrier signal, a digital watermark does not change the size of the carrier signal. The needed properties of a digital watermark depend on the
use case In software engineering, software and systems engineering, the phrase use case is a Polysemy, polyseme with two Word sense, senses: # A usage scenario for a piece of software; often used in the plural to suggest situations where a piece of soft ...

in which it is applied. For marking media files with copyright information, a digital watermark has to be rather robust against modifications that can be applied to the carrier signal. Instead, if integrity has to be ensured, a fragile watermark would be applied. Both
steganography Steganography ( ) is the practice of concealing a message within another message or a physical object. In computing/electronic contexts, a computer file, message, image, or video is concealed within another file, message, image, or video. The wor ...

and digital watermarking employ steganographic techniques to embed data covertly in noisy signals. While steganography aims for imperceptibility to human senses, digital watermarking tries to control the robustness as top priority. Since a digital copy of data is the same as the original, digital watermarking is a passive protection tool. It just marks data, but does not degrade it or control access to the data. One application of digital watermarking is ''source tracking''. A watermark is embedded into a digital signal at each point of distribution. If a copy of the work is found later, then the watermark may be retrieved from the copy and the source of the distribution is known. This technique reportedly has been used to detect the source of illegally copied movies.

# History

The term "Digital Watermark" was coined by Andrew Tirkel and Charles Osborne in December 1992. The first successful embedding and extraction of a steganographic spread spectrum watermark was demonstrated in 1993 by Andrew Tirkel, Charles Osborne and Gerard Rankin. Watermarks are identification marks produced during the paper making process. The first watermarks appeared in Italy during the 13th century, but their use rapidly spread across Europe. They were used as a means to identify the paper maker or the trade guild that manufactured the paper. The marks often were created by a wire sewn onto the paper mold. Watermarks continue to be used today as manufacturer's marks and to prevent forgery.

# Applications

Digital watermarking may be used for a wide range of applications, such as: * Copyright protection * Source tracking (different recipients get differently watermarked content) * Broadcast monitoring (television news often contains watermarked video from international agencies) * Video authentication * Software crippling on
screencasting A screencast is a digital recording of computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known as Comput ...
and
video editing software Video Video is an electronic Electronic may refer to: *Electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses ...
programs, to encourage users to purchase the full version to remove it. *ID card security *Fraud and Tamper detection. * Content management on
social network A social network is a social structure made up of a set of social actors (such as individuals or organizations), sets of Dyad (sociology), dyadic ties, and other Social relation, social interactions between actors. The social network perspectiv ...

s

# Digital watermarking life-cycle phases

The information to be embedded in a signal is called a digital watermark, although in some contexts the phrase digital watermark means the difference between the watermarked signal and the cover signal. The signal where the watermark is to be embedded is called the ''host'' signal. A watermarking system is usually divided into three distinct steps, embedding, attack, and detection. In embedding, an algorithm accepts the host and the data to be embedded, and produces a watermarked signal. Then the watermarked digital signal is transmitted or stored, usually transmitted to another person. If this person makes a modification, this is called an ''attack''. While the modification may not be malicious, the term attack arises from copyright protection application, where third parties may attempt to remove the digital watermark through modification. There are many possible modifications, for example, lossy compression of the data (in which resolution is diminished), cropping an image or video, or intentionally adding noise. ''Detection'' (often called extraction) is an algorithm which is applied to the attacked signal to attempt to extract the watermark from it. If the signal was unmodified during transmission, then the watermark still is present and it may be extracted. In ''robust'' digital watermarking applications, the extraction algorithm should be able to produce the watermark correctly, even if the modifications were strong. In ''fragile'' digital watermarking, the extraction algorithm should fail if any change is made to the signal.

# Classification

A digital watermark is called ''robust'' with respect to transformations if the embedded information may be detected reliably from the marked signal, even if degraded by any number of transformations. Typical image degradations are JPEG compression, rotation, cropping, additive noise, and quantization. For video content, temporal modifications and MPEG compression often are added to this list. A digital watermark is called ''imperceptible'' if the watermarked content is perceptually equivalent to the original, unwatermarked content. In general, it is easy to create either robust watermarks—or—imperceptible watermarks, but the creation of both robust—and—imperceptible watermarks has proven to be quite challenging. Robust imperceptible watermarks have been proposed as a tool for the protection of digital content, for example as an embedded ''no-copy-allowed'' flag in professional video content. Digital watermarking techniques may be classified in several ways.

## Robustness

A digital watermark is called "fragile" if it fails to be detectable after the slightest modification. Fragile watermarks are commonly used for tamper detection (integrity proof). Modifications to an original work that clearly are noticeable, commonly are not referred to as watermarks, but as generalized
barcode A barcode or bar code is a method of representing data in a visual, machine-readable form. Initially, barcodes represented data by varying the widths and spacings of parallel lines. These barcodes, now commonly referred to as linear or one-dime ...

s. A digital watermark is called ''semi-fragile'' if it resists benign transformations, but fails detection after malignant transformations. Semi-fragile watermarks commonly are used to detect malignant transformations. A digital watermark is called ''robust'' if it resists a designated class of transformations. Robust watermarks may be used in copy protection applications to carry copy and no access control information.

## Perceptibility

A digital watermark is called ''imperceptible'' if the original cover signal and the marked signal are perceptually indistinguishable. A digital watermark is called ''perceptible'' if its presence in the marked signal is noticeable (e.g. digital on-screen graphics like a network logo, content bug, codes, opaque images). On videos and images, some are made transparent/translucent for convenience for consumers due to the fact that they block portion of the view; therefore degrading it. This should not be confused with ''perceptual'', that is, watermarking which uses the limitations of human perception to be imperceptible.

## Capacity

The length of the embedded message determines two different main classes of digital watermarking schemes: * The message is conceptually zero-bit long and the system is designed in order to detect the presence or the absence of the watermark in the marked object. This kind of watermarking scheme is usually referred to as ''zero-bit'' or ''presence watermarking schemes''. * The message is an n-bit-long stream $\left\left(m=m_1\ldots m_n,\; n\in\N\right.$, with $\left.n=, m, \right\right)$ or $M=\^n$ and is modulated in the watermark. These kinds of schemes usually are referred to as multiple-bit watermarking or non-zero-bit watermarking schemes.

## Embedding method

A digital watermarking method is referred to as ''
spread-spectrum In telecommunication Telecommunication is the transmission of information by various types of technologies over wire A wire is a single usually cylindrical A cylinder (from Greek Greek may refer to: Greece Anything of, from, or ...
'' if the marked signal is obtained by an additive modification. Spread-spectrum watermarks are known to be modestly robust, but also to have a low information capacity due to host
interference Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extran ...
. A digital watermarking method is said to be of ''quantization type'' if the marked signal is obtained by quantization. Quantization watermarks suffer from low robustness, but have a high information capacity due to rejection of host interference. A digital watermarking method is referred to as '''' if the marked signal is embedded by additive modification which is similar to spread spectrum method, but is particularly embedded in the spatial domain.

# Evaluation and benchmarking

The evaluation of digital watermarking schemes may provide detailed information for a watermark designer or for end-users, therefore, different evaluation strategies exist. Often used by a watermark designer is the evaluation of single properties to show, for example, an improvement. Mostly, end-users are not interested in detailed information. They want to know if a given digital watermarking algorithm may be used for their application scenario, and if so, which parameter sets seems to be the best.

# Cameras

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and
Kodak The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York Rochester ( ...

have produced cameras with security features such as the Epson PhotoPC 3000Z and the Kodak DC-290. Both cameras added irremovable features to the pictures which distorted the original image, making them unacceptable for some applications such as
forensic evidence Forensic identification is the application of forensic science Forensic science, also known as criminalistics, is the application of to and , mainly—on the criminal side—during , as governed by the legal standards of and . Forensic sc ...
in court. According to Blythe and Fridrich, " ither camera can provide an undisputable proof of the image origin or its author". A secure digital camera (SDC) was proposed by Saraju Mohanty, et al. in 2003 and published in January 2004. This was not the first time this was proposed. Blythe and Fridrich also have worked on SDC in 2004 for a
digital camera A digital camera is a camera A camera is an optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behav ...

that would use lossless watermarking to embed a
biometric Biometrics are body measurements and calculations related to human characteristics. Biometrics authentication Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an ...

identifier together with a
cryptographic hash A cryptographic hash function A hash function is any function Function or functionality may refer to: Computing * Function key A function key is a key on a computer A computer is a machine that can be programmed to carry out s ...
.

# Reversible data hiding

''Reversible data hiding'' is a technique which enables images to be authenticated and then restored to their original form by removing the digital watermark and replacing the image data that had been overwritten. This would make the images acceptable for legal purposes. The US Army also is interested in this technique for authentication of
reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain Relief map of Sierra Nevada, Spain Terrain or relief (also topographical Topogr ...

images.

# Watermarking for relational databases

Digital watermarking for
relational database A relational database is a digital database In , a database is an organized collection of stored and accessed electronically from a . Where databases are more complex they are often developed using formal techniques. The (DBMS) is the tha ...
s has emerged as a candidate solution to provide copyright protection, tamper detection, traitor tracing, and maintaining integrity of relational data. Many watermarking techniques have been proposed in the literature to address these purposes. A survey of the current state-of-the-art and a classification of the different techniques according to their intent, the way they express the watermark, the cover type, granularity level, and verifiability was published in 2010 by Halder et al. in the
Journal of Universal Computer Science The ''Journal of Universal Computer Science'' (''J.UCS'') is a monthly peer-reviewed Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work ( peers). It functions as a form of self-r ...
.

* Coded Anti-Piracy * Copy attack * EURion constellation * Pattern Recognition (novel) *
Steganography Steganography ( ) is the practice of concealing a message within another message or a physical object. In computing/electronic contexts, a computer file, message, image, or video is concealed within another file, message, image, or video. The wor ...

*
Traitor tracing Traitor tracing schemes help trace the source of leaks when secret or proprietary data is sold to many customers. In a traitor tracing scheme, each customer is given a different personal decryption key. (Traitor tracing schemes are often combined w ...
*
Watermark (data file) A watermark stored in a data file refers to a method for ensuring data integrity which combines aspects of hash function, data hashing and digital watermarking. Both are useful for tamper detection, though each has its own advantages and disadvanta ...
* Audio watermark *
Digital on-screen graphic A digital on-screen graphic (originally known as digitally originated graphic, and known in the UK and New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—th ...
*
Automatic content recognition Automatic content recognition (ACR) is an identification technology to recognize content played on a media device or present in a media file. Devices containing ACR support enable users to quickly obtain additional information about the content they ...

# References

ECRYPT report: Audio Benchmarking Tools and Steganalysis

ECRYPT report: Watermarking Benchmarking
* Jana Dittmann, David Megias, Andreas Lang, Jordi Herrera-Joancomarti; ''Theoretical framework for a practical evaluation and comparison of audio watermarking schemes in the triangle of robustness, transparency and capacity''; In: Transaction on Data Hiding and Multimedia Security I; Springer LNCS 4300; Editor Yun Q. Shi; pp. 1–40; ,200
PDF
* * Patrick Bas, Teddy Furon, François Cayre, Gwenaël Doërr, Benjamin Mathon, "Watermarking Security, Fundamentals, Secure Designs and Attacks", Springer Briefs in Electrical and Computer Engineering, 2016,

Batch Watermark

Digital Watermarking Alliance

Digital Watermarking & Data Hiding research papers
at forensics.nl
Information hiding homepage
by Fabien Petitcolas
Robust Mesh Watermarking

Watermarking Lecture
{{DEFAULTSORT:Digital Watermarking Authentication methods Watermarking Digital photography