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Saturday, March 16, 2013

Attacks@Image WaterMarking

1.    We keep exploring new grounds but also without realizing the pits it offers,we start playing games on it.Such is the world of IT,we keep discovering so many new technologies to strengthen and exploit for our use and we keep ourselves vulnerable!!!!

2.   Without wasting more words,this post would briefly mention about Image water marking and the type of attacks it remains vulnerable to.So first whats Image Water Marking??...an easy way to describe digital watermark is simply comparing it to a traditional paper watermark or a power point water mark which most of us might have even used at some point of time.Like Traditional watermarks offer proof of authenticity by being imperceptible, digital watermarks offer a way that allows a computer to read the mark but not by the human 6/6 eye....there are actually four essential parameters which are commonly used to determine the quality of water marking these are :

- Robustness
- Imperceptibility
- Payload 
- Security

3.   Now each of these parameters has a unique characteristic that makes the purpose of image water marking strong and adaptable.So when we speak about attacks on image water marking...the attacks again are classified as :

- Image Compression Attack : Primarily used to reduce the size of image in transmission.The original image remains most of it that it was but requires lesser bandwidth to move.

- Image Contrast Attack : To a human eye a slight change in contrast of colors makes a huge difference in overall perception

- Cropping Attack : A part of image gets cropped from original

Re sizing Attack : The image gets re sized from the original coords

- Rotation Attack : A simple clockwise or a anticlockwise attack would rotate the image from its original coords


Another categorization of the image water marking attacks contains four classes :(Source here : Abhishek Goswami)

Removal Attacks : Aim at the complete removal of the watermark information from the watermarked data without cracking the security of the watermarking algorithm

Geometric Attacks : Do not actually remove the embedded watermark itself, but intend to distort the watermark detector synchronization with the embedded information.

Cryptographic Attacks : Cryptographic attacks aim at cracking the security methods in watermarking schemes and thus finding a way to remove the embedded watermark information or to embed misleading
watermarks.

Protocol Attacks : Aim at attacking the entire concept of the watermarking application. This type of attack is based on the concept of invertible watermarks. The idea behind inversion is that the attacker subtracts his own watermark from the watermarked data and claims to be the owner of the watermarked data. This can create ambiguity with respect to the true ownership of the data. 




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