5 Different Types of Forensic Watermarking Techniques
Forensic watermarking helps content creators protect their digital content by allowing them to embed information with regards to the ownership and source of the content. Many different types of watermarks can be used for this purpose. Five of the most common types of watermarks are discussed in this post.
With the increasing cases of online piracy, content creators are now gravely concerned about the security of their digital content. From videos, music, images, to eBooks, any and every type of online content is under severe threat of illegal downloads, usage, and duplication.
Using forensic or digital watermark is one of the most effective ways in which content creators can protect their content. Similar to traditional watermarks, a digital watermark embeds visible or invisible information about the ownership and source into the digital content. Depending on the needs of the content creators, there are many different types of digital watermarks. Five of the most popular ones are-
- Visible Watermark
As the name suggests, a visible watermark is something that can be seen with the human eyes. They are also known as overt watermarks and are generally semi-transparent images that are overlaid on top of the original content like a photograph with the name of the photographer or company which holds the copyright.
Special attention is given to make sure that the visible watermark cannot be easily cropped or removed without damaging the photograph.
- Invisible Watermark
Invisible watermarks cannot be seen with human eyes, but devices like computer, DVD players, and digital cameras can detect them with the help of specialised software. They are also known as covert watermarks and are embedded into the digital content file for proving the authenticity of the content or identifying the owner or copyright holder.
Some types of invisible watermarks can also be used for monitoring and tracking distribution of the content to prevent illicit downloading, copying, or posting.
- Frequency Watermark
Frequency watermark is also a type of invisible watermark which is applied to an image at a particular frequency or spectral coefficient. This type of watermark is only visible when the frequency is separated from the image. As compared to a standard invisible watermark, a frequency watermark is known to offer a higher level of protection.
There are many different types of transforms, like Discrete Cosine, Discrete Wavelength, Discrete Hadamard, and Discrete Laguerre that are used with frequency watermarks.
- Spatial Watermark
Spatial watermark is a type of watermark which is applied to a particular colour band of the content like image. It can only be seen when all the other colours are separated from the image. There are two common types of spatial watermarks- Least Significant Bit (LSB) and Spread Spectrum Modulation (SSM).
With the LSB technique, the watermark is added to the last or least significant bit of the image. In SSM, specific algorithms are used for embedding information into the image. For this, the host image is linearly combined with a noise signal which is modulated via the watermark.
- Reversible Watermarks
One of the most common watermarking techniques is reversible watermarking. Visible watermarks are generally superimposed in a way that the watermark covers the entire image or at least the vital part of the image. This prevents common watermark attacks like cropping. Reversible watermarks make use of cryptographic methods to put a temporary watermark on the image.
With correct authorisation and authentication, the watermark can then be removed from the picture to reveal the original picture. For instance, if someone legally purchases a picture, a password or key can be provided for accessing the original work.
Selecting the Right Watermarking Technique
As compared to visible watermarks, invisible watermarks are known to be more effective. However, in a lot of cases, visible watermarks prove to be a better choice. While using watermarks was known to be a complex and expensive process for content creators, owners, and distributors, the availability of cloud-based watermarking services has eliminated these complications.
Some of the service providers also offer pay-as-you-go pricing models to ensure watermarking adoption is no longer an expensive affair for the original content owners or copyright holders.
