The copy attack is an attack on certain
digital watermarking
A digital watermark is a kind of marker covertly embedded in a noise-tolerant signal such as audio, video or image data.H.T. Sencar, M. Ramkumar and A.N. Akansu: ''Data Hiding Fundamentals and Applications: Content Security in Digital Multimedia'' ...
systems proposed by M. Kutter, S. Voloshynovskiy, and A. Herrige in a paper presented in January, 2000 at the Photonics West
SPIE
SPIE (formerly the Society of Photographic Instrumentation Engineers, later the Society of Photo-Optical Instrumentation Engineers) is an international not-for-profit professional society for optics and photonics technology, founded in 1955. It ...
convention.
In some scenarios, a digital watermark is added to a piece of
media
Media may refer to:
Communication
* Means of communication, tools and channels used to deliver information or data
** Advertising media, various media, content, buying and placement for advertising
** Interactive media, media that is inter ...
such as an
image
An image or picture is a visual representation. An image can be Two-dimensional space, two-dimensional, such as a drawing, painting, or photograph, or Three-dimensional space, three-dimensional, such as a carving or sculpture. Images may be di ...
,
film
A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...
, or
audio clip, to prove its authenticity. If a piece of media were presented and found to lack a watermark, it would be considered suspect. Alternatively, a security system could be devised which would limit a user's ability to manipulate any piece of media which contained a watermark. For instance, a
DVD burner may prohibit making copies of a film which contained a watermark.
The copy attack attempts to thwart the effectiveness of such systems by estimating the watermark given in an originally watermarked piece of media, and then adding that watermark to an un-watermarked piece. In the first scenario listed above, this would allow an attacker to have an inauthentic image declared authentic, since it contains a watermark. In the second scenario, an attacker could flood the market with content which ordinarily would allow a user to manipulate it as he saw fit, but due to the presence of the watermark, limitations would be imposed. In this way, schemes which sought to limit use of watermarked media may prove to be too unpopular for wide distribution.
In a 2003 paper presented at the
,
[J. Barr, B. Bradley, and B. Hannigan]
Using Digital Watermarks with Image Signatures to Mitigate the Threat of the Copy Attack
Proceedings of ICASSP, 2003 John Barr, Brett Bradley, and Brett T. Hannigan of
Digimarc
Digimarc Corporation is a provider of enterprise software and services. The company's software, which includes digital identifiers (i.e., serialized QR codes and digital watermarks), is designed to address counterfeiting, product authenticity ...
describe a way to tie the content of the digital watermark to the underlying image, so that if the watermark were placed into a different image, the
watermark detection
An audio watermark is a unique electronic identifier embedded in an audio signal, typically used to identify ownership of copyright. It is similar to a watermark on a photograph.
Digital watermarking is the process of embedding information into a ...
system would not authenticate it.
References
{{reflist
Computer security exploits
Watermarking