What are Blind, Semi-blind and Non-blind Watermarking Systems?

What are Blind, Semi-blind and Non-blind Watermarking Systems?


Digital watermarking systems can be grouped in three schemes - they are Blind, Semi-blind and Non-blind.


Blind watermarking scheme is also known as public watermarking scheme. This is the most challenging type of watermarking system as it requires neither the cover (original data), I nor the embedded watermark, W. These systems extract n bits of the watermark data from the watermarked data (i.e the watermarked image).


I' x K -> W


Note: I' is the watermarked data, K is the key


Semi-blind watermarking scheme is also known as semi-private watermarking scheme. This system does not require the cover (original data) for detection. The purpose of this system to find whether that the watermark can be detected.


I' x K x W -> {0,1} 


Some applications of systems under this scheme are for copyright protection (ownership), copy control (i.e as in DVD where copying is not allowed) and fingerprinting where the goal is to identify the original recipient of the pirated copies. 


Non-blind watermarking scheme is also known as private watermarking scheme. This system requires at least the cover (original data) for detection. Type I systems extract the watermark W from the possibly distorted data I' and use the original data as a hint to find where the watermark could be in I'.


Type II systems also require a copy of the embedded watermark for extraction and yield "yes" or "no" answer to the question whether the watermark data exists.


I x I' x K x W -> {0,1} 


This scheme is to be believed as the most robust than the other schemes as it exchanges very little information and requires access to secret material.