Digital watermark
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A digital watermark could be anything from a clearly visible overlayed semi-transparent copyright notice, to a [[Steganography|steganographic]] technique that makes the signature virtually undetectable, or anything in between. It could be a simple notice of what software created the file, or it could contain detailed tracking information intended to help figure out who created the file. | A digital watermark could be anything from a clearly visible overlayed semi-transparent copyright notice, to a [[Steganography|steganographic]] technique that makes the signature virtually undetectable, or anything in between. It could be a simple notice of what software created the file, or it could contain detailed tracking information intended to help figure out who created the file. | ||
| − | Calling something a "watermark" usually implies that it is designed to survive at least minor modifications to the document. | + | Calling something a "watermark" usually implies that it is designed to survive at least minor modifications to the document. Indeed the major difference between steganography and watermarking is that steganography is focused on packing as much data into a file as possible at the cost of robustness while watermarking puts just enough data to ID the author/file but tries to be robust enough that format conversions, resizing, cropping, etc don't impact the ability to read that data. |
Similar to [[bar codes]], some kinds of watermarks store digital data in physical/analog documents. See [[Watermark (physical)]]. | Similar to [[bar codes]], some kinds of watermarks store digital data in physical/analog documents. See [[Watermark (physical)]]. | ||
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| + | == Software == | ||
| + | * [[OpenStego]] | ||
| + | * [[wbStego]] - has a minor PDF watermarking function | ||
== See also == | == See also == | ||
Revision as of 16:55, 31 August 2023
A digital watermark is a kind of digital signature, usually in the form of a subtle modification to the main content of an image, audio, or video file. To put it another way, a digital watermark stores metadata inside the main content of a file, instead of separately. There are a number of different reasons for using a watermark, but the main point is to make it difficult to remove the metadata.
A digital watermark could be anything from a clearly visible overlayed semi-transparent copyright notice, to a steganographic technique that makes the signature virtually undetectable, or anything in between. It could be a simple notice of what software created the file, or it could contain detailed tracking information intended to help figure out who created the file.
Calling something a "watermark" usually implies that it is designed to survive at least minor modifications to the document. Indeed the major difference between steganography and watermarking is that steganography is focused on packing as much data into a file as possible at the cost of robustness while watermarking puts just enough data to ID the author/file but tries to be robust enough that format conversions, resizing, cropping, etc don't impact the ability to read that data.
Similar to bar codes, some kinds of watermarks store digital data in physical/analog documents. See Watermark (physical).
