Watermarking and Steganography by zrl90908


									Watermarking and
• 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
                                               J. Plank Features
    • Pressed into paper                       •In-house watermark design
                                               •Computerized design process
      during paper-making                      •Quick-change sleeves and
                •Dandy roll
             •7.25" diameter
          •Watermarking possible

              Dandy Roll
• Wet pulp sprayed    •High grade stainless steel construction
  onto moving belt    •Incorporates internal oscillating shower,
                      internal pan, internal steam shower and
• Dandy Roll          external saveall pan
                      •Extended Header Brush for easy cleaning
  pressed into pulp   of shower pipe

• Dandy Roll looks
  like oversized
  printer‟s roll
  covered with
   Laser Printed “Watermarks”
• Used on bond
  paper, but who
  uses bond
  – Doesn‟t work
    well in inkjets
    or laserjets
• “Watermarks”
  with most print
         Printed Watermarks
• Looks great
• You can even put it in
  your PDF file…which
  is the problem!
• No security
  Printed Document Authentication
• 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
• 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
• 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
   – X is the ticket
   – Record h(h(X)) on DVD
   – Provided with X, DVD recorded stores h(X) on second-
     generation 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
• A hidden message that can't be found by
• 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
  – 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
     • 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.
• 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
• 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/bitleve
• Encoding information through list order:
  – http://www.wayner.org/books/discrypt2/sorted.
               JPEG Watermarking

“Hide and Seek: An
                                 Figure 2. Embedded information in a
Introduction to Steganography”
                                 JPEG. (a) The unmodified
IEEE Security & Privacy
                                 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
  – Earn up to $10,000 for breaking their “watermarks”
  – Challenge from September 15, 2000 – October 7,
• 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
• Leading provider of
• Plug-ins for Windows,
  PhotoShop, etc.
• Communicates:
  – Copyright ownership
  – Image ID
  – Image content – adult,
        Tools and References
• Fabien a. p. penticolas
  – http://www.petitcolas.net/fabien/steganography/
• Digimarc
• http://theargon.com/archivess/steganograp
• Hiding Secrets with Steganography, by
  Dru Lavigne,
  – http://www.onlamp.com/pub/a/bsd/2003/12/04
• http://www.outguess.org
                  “Mosaïc attack”

• Defeat an embedded watermark by
  chopping up image and serving it in pieces
   <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">
   <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">
          Mosaïc assembled

• Some websites use mosaics to deter casual
• 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
• “Weak but better than the MPEG copyright flag
  defined in the standard”
• Defeat by decompressing & recompressing
  MP3Stego in action


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