Transcript Watermarking and Steganography

Watermarking and
Steganography
Watermarks
• First introduced in Bologna, Italy in 1282
• Dandy Roll presses pattern into drying paper
– Changes thickness of paper fibers
• Uses:
–
–
–
–
By paper makers to identify their product
Security for stamps, official documents.
Stock certificates, money, etc.
Chic
• Other “watermarks”
– Printing on plastic with a window.
(Australian $10 note)
Dandy Roll
• Pressed into paper
during paper-making
process
J. Plank Features
•In-house watermark design
•Computerized design process
•Quick-change sleeves and
sections
•Dandy roll
•7.25" diameter
•Watermarking possible
http://www.uwsp.edu/papersci/PM/Machine/Dandy.htm
Dandy Roll
• Wet pulp sprayed
onto moving belt
• Dandy Roll
pressed into pulp
• Dandy Roll looks
like oversized
printer’s roll
covered with
pattern
•High grade stainless steel construction
•Incorporates internal oscillating shower,
internal pan, internal steam shower and
external saveall pan
•Extended Header Brush for easy cleaning
of shower pipe
Laser Printed “Watermarks”
• Used on bond
paper, but who
uses bond
paper?
– Doesn’t work
well in inkjets
or laserjets
• “Watermarks”
with most print
drivers…
Printed Watermarks
• Looks great
• You can even put it in
your PDF file…which
is the problem!
• No security
Printed Document Authentication
Techniques
• Microprinting – Print that is too small to produce or copy
with conventional equipment
• Intaglio –engraved pattern used to press ink with great
force; raised letters
• Letterpress – Ink rolled raised type, leaving depression.
Used for printing numbers.
• Simultan press – precise registration of front and back.
(see-through register). Changing ink colors (rainbowing).
• Optically variable inks (change color depending on
angle)
• Metal foils & threads embedded in paper
• Security holograms
Lessons for paper authentication
• Security features should convey a message
relevant to the product.
– Use iridescent ink to print the banknote denomination
• Should obviously belong where they are
– They become “embedded in the user’s cognitive
model.”
• Should be obvious
• Should not have competitors
• Should be standardized
Source: Security Engineering, Anderson
Information Hiding
• Copyright Marks:
– Watermarks - Hidden copyright messages
– Fingerprints – Hidden serial numbers
• Steganography
– Hidden messages.
• Other applications:
– Closed captioning (hidden in first 21 scan lines)
• http://www.robson.org/gary/writing/nv-line21.html
– Audio RDS (Radio Data Service)-like service
• “What’s that song?”
Watermarks for Copyright Policy
• “never copy”
• “copy only once”
• “copy only at low quality”
JPMG Linnartz, “The ‘Ticket’ Concept for Copy Control
Based on Embedded Signaling” (Anderson [504] )
Suggests a hash-based implementation of “copy only
once:”
– X is the ticket
– Record h(h(X)) on DVD
– Provided with X, DVD recorded stores h(X) on secondgeneration copy.
The Broadcast Flag
• “Advanced Television Systems Committee Flag”
• Enable/Disable:
– high-quality digital output
– Re-transmitting on an “unprotected” channel
• In the future:
– Time-shifting?
– Disallow fast-forward through commercials
• Required on all digital TV cards sold after July 2005
• Only broadcast, not satellite or cable-transmitted.
“Losing Control of Your TV,” Technology Review, March 3, 2004
http://www.technologyreview.com/articles/04/03/wo_garfinkel030304.asp?p=1
Steganography
• A hidden message that can't be found by
humans
• A hidden message that can't be found by
an algorithm.
A hidden message that can be found by an
algorithm but not by a human.
• A hidden message that can be found by
some algorithms but not others.
[Wayner 2004]
What is Hidden?
Defining "Hidden" is not easy
– We run into the usual Goedel limits that prevents us
from being logical about detection.
– Humans are very different. Some
musicians have very, very good ears.
– Some algorithms leave statistical anomalies. The
message is often more random than the carrier
signal. These statistics can give away the message.
Who wants it?
• Evil doers. If evil messages can't be seen by good
people, evil will triumph. Osama bin Laden?
• Good doers. If the good guys can communicate in
secret, then good
will triumph. U.S. forces
• Content owners and copyright czars. Hidden messages
can carry information about rights to view, copy, share,
listen, understand, etc.
• Software Developers. "Hidden" channels can be added
to data structures without crashing previous versions.
Steganography can fight bit rot.
Models for Steganography
• Replace random number generators with the
message.
– This works if the random numbers are used in a detectable way.
– TCP/IP, for instance, uses a random number for connections.
Some grab this for their own purposes.
• Replace noise with the message.
– Just replace the least-significant bit.
– Avoid the noise and tweak the salient features.
• Anything not affected by compression.
– If you have the freedom to change data without hurting the data,
then you have the freedom to include another message.
Models for Steganography
• Structured Models
– Run some compression algorithm in reverse
• If the compression models the data accurately, then running
it in reverse should spit out something that models the data
well.
• Huffman algorithms give common letters short bit strings and
rare ones long ones.
– Change the structure or the order.
• GifEncoder, for instance, changes the order of the colors in
the palette.
– Synthesize something new and use the data to guide
the synthesis.
• Is the ghoul shooting at you in the game using a revolver or a
machine gun? That's one bit.
Noise
• The least significant bit of pixels or sound
files is very popular.
• Tweaking the LSB is only a small change.
Less than 1%.
– 140=10001100
– 141=10001101
• You can encrypt, too!
LSB modified to hide info
LSB Modification
• Side Effects:
– The data may not have the same statistical
pattern as the least significant bits being
replaced.
• Add a lot of noise, and it’s obvious
4 LSB modified produces banding
More LSB Modification
6 bits
7 bits
8 out of 8 bits
All 8 bits
Bit 8 vs. Bit 1
Wayner Demos
• Information hiding at the bit level:
– http://www.wayner.org/books/discrypt2/bitlevel
.php
• Encoding information through list order:
– http://www.wayner.org/books/discrypt2/sorted.
php#note2
JPEG Watermarking
“Hide and Seek: An
Introduction to Steganography”
IEEE Security & Privacy
Figure 2. Embedded information in a
JPEG. (a) The unmodified
original picture; (b) the picture with the first
chapter of The Hunting
of the Snark embedded in it.
Mesh Watermarking
• Robust mesh watermarking, Emil Praun,
Hugues Hoppe, Adam Finkelstein,
July 1999
Proceedings of the 26th annual
conference on Computer graphics and
interactive techniques
Issues to evaluate
• “Capability”
– Payload carrying ability
– Detectability
– Robustness
• Securing information: Capacity is the wrong
paradigm, Ira S. Moskowitz, LiWu Chang,
Richard E. Newman ,
September 2002 Proceedings of the 2002
workshop on New security paradigms
SDMI –
Secure Digital Media Initiative
• SDMI (200+ companies) published an “Open
Letter to the Digital Community” with an SDMI
Challenge.
– Earn up to $10,000 for breaking their “watermarks”
– Challenge from September 15, 2000 – October 7,
2000
• SDMI Systems:
– Designed to prevent “remixing” of privated CDs
– Designed to survive MP3 compression
SDMI & The Academics
• The Academics:
– Scott Craver, Patrick McGregor, Min Wu, Bede Liu,
(Dept. of Electrical Engineering, Princeton University)
– Adam Stubblefield, Ben Swartzlander, Dan S. Wallach
(Dept. of Computer Science, Rice University)
– Edward W. Felten (Dept. of Computer Science,
Princeton University)
• What they did:
– Successfully removed the digital watermark from the
challenge audio samples.
• How did they know they did it?
– SDMI provided an “Oracle” that told them they did!
SDMI & Academics: Part 2
• Academics couldn’t claim cash prize
– Doing so would have required signing a “confidentiality agreement” and
prohibit the academics from sharing results with the public
• DMCA didn’t apply…
– … because SDMI specifically invited the work
• Felton &c decided to present their findings at the 4th International
Information Hiding Workshop April 25-29, 2001
• April 9, 2001 RIAA Senior VP for Business and Legal Affairs sent
Felton letter with veiled DMCA threats
• April 26, 2001 Felton declines to present paper
• May 3, 2001 – RIAA and SDMI say they never intended to sue
• June 6, 2001 – Felton files suit against RIAA asking for a
declaratory judgment that they would not be infringing
• November 28, 2001 – Case dismissed for mootness
DigiMarc
• Leading provider of
watermarking
technologies
• Plug-ins for Windows,
PhotoShop, etc.
• Communicates:
– Copyright ownership
– Image ID
– Image content – adult,
etc.
Tools and References
• Fabien a. p. penticolas
– http://www.petitcolas.net/fabien/steganography/
• Digimarc
• http://theargon.com/archivess/steganograp
hy/
• Hiding Secrets with Steganography, by
Dru Lavigne,
– http://www.onlamp.com/pub/a/bsd/2003/12/04
/FreeBSD_Basics.html
• http://www.outguess.org
“Mosaïc attack”
• Defeat an embedded watermark by
chopping up image and serving it in pieces
<nobr>
<img SRC="kings_chapel_wmk1.jpg’ BORDER="0’ ALT="1/6’ width="116’ height="140">
<img SRC="kings_chapel_wmk2.jpg’ BORDER="0’ ALT="2/6’ width="116’ height="140">
<img SRC="kings_chapel_wmk3.jpg’ BORDER="0’ ALT="3/6’ width="118’ height="140">
</nobr>
<br>
<nobr>
<img SRC="kings_chapel_wmk4.jpg’ BORDER="0’ ALT="4/6’ width="116’ height="140">
<img SRC="kings_chapel_wmk5.jpg’ BORDER="0’ ALT="5/6’ width="116’ height="140">
<img SRC="kings_chapel_wmk6.jpg’ BORDER="0’ ALT="6/6’ width="118’ height="140">
</nobr>
Mosaïc assembled
• Some websites use mosaics to deter casual
copying!
MP3Stego
• Hides information in MP3 files during the
compression process
• Takes advantage of the fact that MP3 provides
high-quality compression of 11:1
– Plenty of room for information hiding!
– Randomly chooses which parts of the Layer III inner
loop to modify; makes sure modifications don’t
exceed threshold defined by the psycho acoustic
model.
• “Weak but better than the MPEG copyright flag
defined in the standard”
• Defeat by decompressing & recompressing
MP3Stego in action
http://www.petitcolas.net/fabien/steganography/mp3stego/index.html