Re: [WM]: about RST attacks

[Kieran Larkin <kieran.larkin@cisra.canon.com.au>]

At 04:25 PM 26/04/2005, you wrote:
>HI, all, i amBODY bgColor=#ffffff> now in research in RST attack
>in  digital watermarking. as to most methods, they refer the
>RST,merely mean  the attacks don't include croping, that is the image
>size changes when  rotating ,and as to transaltion, they also mean
>just transalte in a  background, without cropping. but as to the
>image, it seems no meaning.  another RST is include croping attacks,
>which can't be represented by the 
>linear equation [ x y]=[s 0;0 s]*[cosa -sina;sina cosa][x' y']+[a
>b]ĄŁ can 
>anyone tell me some useful method to deal with the second RST types?
>the  Invariant domain based on moments are all related with  no cropping.


Moment-based RST tolerant watemarking methods are (very) sensitive to=  cropping.

Currently there are several other RST invariant watermarking methods  available in the published literature.
Unfortunately it is not easy to find out about these without carefully  searching the literature using tools like Google, Inspec,
Citeseer, and  Current Contents.  If you require a text book answer you may find the  information at least 5 years out of date -
which can be significant in a  area such as watermarking.

So I will leave the comprehensive literature review to someone starting  their doctoral thesis and mention just one RST method
that is also  insensitive to cropping.  I admit a certain lack of impartiality in my  choice of this method, but it should give
you a good starting point for  your research in RST attacks:

Fletcher, P. A. & Larkin, K. G. in IH2002, Fifth International Workshop on=   Information Hiding ,Noordwijkerhout, The
Netherlands, 2002, ed. Petitcolas,=   F. A. P., p 129-144, Springer Verlag, Lecture Notes in Computer Science,  LNCS 2578 .

http://www.springerlink.com/app/home/contribution.asp?wasp=8b19de4cfba148e0820f1ba8bad85848&referrer=parent&backto=issue,9,27;journal,851,1976;linkingpublicationresults,1:105633,1

Abstract:

A common goal of many watermarking techniques is to produce a mark that  remains detectable after the geometric transformations of
Rotation, Scale  and Translation; also known as RST invariance. We present a simple approach=   to achieving RST invariance
using pixel-by-pixel addition of oscillating  homogeneous patterns known as Logarithmic Radial Harmonic Functions  [LRHFs].
LRHFs are the basis functions of the Fourier-Mellin transform and=   have perfect correlation, orthogonality, and spread-spectrum
properties.  Once the patterns have been embedded in an image they can be detected  directly regardless of RST and with great
sensitivity by correlation with  the corresponding complex LRHFs. In contrast to conventional methods our  approach is
distinguished by the utilization of signal phase information  and the absence of interpolation artifacts. Data encoding is based
on the  information in the relative centre positions of multiple spatially  overlapping patterns.



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