[WM]: Bows2, the second challenge on Watermarking is launched !

[Patrick Bas <Patrick.Bas@inpg.fr>]

Dear watermarkers, we have the pleasure to announce the opening of the
second BOWS (Break Our Watermarking System) challenge.

  -One Challenge, 3 Episodes -


The challenge is directly reachable from :

http://bows2.gipsa-lab.inpg.fr


Note that this challenge is divided into 3 Episodes of 3 months each and
the first one starts today !

For more informations on the different Episodes and their rules (aka
"Ep1: Watermarking Robustness", "Ep2: Sensitivity" and "Ep3: Security"),
please visit:

http://bows2.gipsa-lab.inpg.fr/index.php?mode=3DVIEW&tmpl=3Dindex2

Now, it is time to sharpen your own arrows !

Best regards,

Patrick Bas and Teddy Furon


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Rules of Bows-2

General objectives

The general aim of BOWS-2 contest is to investigate how and when an
image watermarking system can be broken though preserving the highest
possible quality of the content. It is not intended to prove how
well-performing a specific watermarking technique is. But it is expected
that, thanks to this contest, the watermarking community will have a
better understanding of the impact of the disparate attacks, perhaps
unknown at the moment, the BOWS-2 participants will carry out, and hence
have a better estimate of how robust watermarking (in general) is when
attacked by a large set of attackers.

BOWS-2 contest is divided into 3 sequential challenges, hereafter named
episodes, to study the robustness and security of watermarking under
three different scenarios. For each episode the goal is the same:
- remove the watermark on 3 different images that are watermarked with
the same key using the same system,
- minimise the average distortion.
Only the conditions to attack the system are different.
Note also that the images have been watermarked with a PSNR between
42.5dB and 42.6dB.

Episode 1: Robustness against image processing

- Period:
Jul 17, 2007 - Oct 17, 2007

- Objectives:
The objectives of the first challenge are to evaluate the basic
robustness of the proposed watermarking scheme to image processing
operations during 3 months. During this period no information about the
watermarking algorithm will be provided and the numbers of trials per
day will be limited. Participants that might want to attack the system
by providing numerous trials have to wait for "Episode 2: sensitivity".

- Rules:
R1.1: Only 30 attempts/day per participant are allowed (if you want to
do more, please wait for Episode 2).
R1.2: Conditions to enter in the Hall of Fame:
- no watermark has to be detected on the 3 uploaded images.
- the average PSNR between the watermarked and the attacked images must
be greater than 20dB (note that the average PSNR is computed as the PSNR
of the mean of the distortions for the 3 images and not the mean of the
3 PSNRs).
- only the 20 highest average PSNRs are listed. Hence, people might go
out of the Hall of Fame as new participants succeed to hack the three
images with a higher average PSNR.
R1.3: The first participant in the Hall of Fame at the end of the
episode wins a prize.
R1.4: The winner will have to send the attacked and successful images to
the organisers and to provide a description of the attack.

Episode 2: Sensitivity against oracle attacks

- Period:
Oct 17, 2007 - Jan 17, 2008

- Objectives:
The objective of Episode 2 is to assess the robustness of the
watermarking technique when the attacker has access to a sealed black
box detector. The watermarking technique is not disclosed, but, we offer
the possibility to perform a very large number of trials, as required by
so-called "sensitivity" or "oracle" attacks.

- Rules:
R2.1: The number of attempts/day is not restricted as far as our server
can handle it.
R2.2: In order to decrease to load of the BOWS-2 server, a binary
executable performing detection will be provided on request (a licence
usage agreement between the two parties has to be signed first). This
executable only works on a typical unix based platform (linux, osX.4).
It uses a different secret key than the one of the contest. 3
watermarked images with this key are also provided. With this software,
participants can fine-tune their attacks, and when ready, they can lead
it on the BOWS-2 images.
R2.3: Conditions to enter in the Hall of Fame and to win: same as R1.2
and R1.4 respectively.


Episode 3: Security against information leakages

- Period:
Jan 17, 2008 - Apr 17, 2007

- Objectives:
The objective of the last episode is to assess the security level
against attackers who estimate the watermark or the secret key used by
the system. In order to do this, BOWS-2 provides a database of 10000
images (watermarked using the same key), the source-code of the
embedding and the detection algorithms and a description of the system.
The attackers try to get information of the secret key by analysing both
the algorithms and the database. Note that providing the source code and
the description of the watermarking system fits with the Kerckhoffs
principle in cryptanalysis.

- Rules:
R3.1: Only 30 attempts/day per participant are allowed.
R3.2: The source code of the embedding and detection scheme is provided
to the participants who sign a license agreement. This license agreement
restricts the use of the watermarking technique to the BOWS-2 contest.
R3.3: A database of 10000 watermarked images will be available for
download to participants who sign a usage agreement. These pictures can
not be used for any other purpose.
R3.4: Conditions to enter in the Hall of Fame and to win: same as R1.2
and R1.4 respectively.









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