2Mosaic 0.2.2 for Microsoft Windows 95/98/NT
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2Mosaic is a 'presentation' attack against digital watermarking systems,
which is of quite general applicability and which possesses the initially
remarkable property that a marked image can be unmarked and yet still
rendered in exactly the same way as the marked image by a standard browser.

The attack was motivated by a fielded automatic system for copyright piracy
detection, consisting of a watermarking scheme plus a web crawler that
downloads pictures from the net and checks whether they contain a watermark.

It consists of chopping an image up into a number of smaller subimages,
which are embedded in a suitable sequence in a web page. Common web
browsers render juxtaposed subimages stuck together, so they appear
identical to the original image. This attack appears to be quite general;
all marking schemes require the marked image to have some minimal size
(one cannot hide a meaningful mark in just one pixel). Thus by splitting
an image into sufficiently small pieces, the mark detector will be
confused. The best that one can hope for is that the minimal size could be
quite small and the method might therefore not be very practical.

The current version of 2Mosaic can only read and produce JPEG files. We hope
to implement other image formats in future versions.

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Usage: 2Mosaic [size] <file_name>

2Mosaic takes the name of a JPEG file as argument and produce several
smaller images and an HTML file. All these files use the same basename.
The default size of these square is 100x100 pixels. It can be changed
by giving an integer between 16 and 100 as first argument.

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Example:

2mosaic 80 testimage.jpg

produces

testimage.html
testimage1.jpg ... testimage<n>.jpg
where <n> depends on the size of the original picture.

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Fabien Petitcolas <fapp2@cl.cam.ac.uk>
<http://www.cl.cam.ac.uk/~fapp2/watermarking/image_watermarking/>


This software is based in part on the work of the Independent JPEG Group.

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