Digital Watermarking

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					 Multimedia Security
Part I: Digital Watermarking

                 Subrata Acharya
               CS 2310, Spring 2007
       Digital Watermarking?
   Allows users to embed some data into digital

   When data is embedded, it is not written at
    header part but embedded directly into
    digital media itself by changing media
    contents data
How It Works
Data Hiding
              Types of Watermark
   Visible
       A visible translucent
        image which is
        overlaid on the
        primary image
   Invisible
       An overlaid image
        which cannot be
        seen, but which can
        be detected
           Visible Watermark
   Logo or seal of the organization which holds
    the rights to the primary image, it allows the
    primary image to be viewed, but still marks it
    clearly as the property of the owning

   Overlay the watermark in a way which makes
    it difficult to remove, if the goal of indicating
    property rights is to be achieved.
Visible Watermark
          Invisible Watermark
   Embedding level is too small to notice
   Can be retrieved by extraction
   Applications:
       Authentication
       Copyrighting
       Etc…
Invisible Watermark
        Embedding Techniques
   Spatial domain
       Original needed
       Original not needed

   Frequency domain
       Original needed
       Original not needed

   Spread domain
Spatial Domain
               Frequency Domain
   Watermarking signal to embed
    X  x0 , x1 ,..., xN
   Host signal
    V  v0 , v1 ,..., v N
   Frequency components
    F  f 0 , f1 ,..., f N
   Embedding
    fi  fi  xi
   Extraction
    xi  fi  fi
Frequency Domain
Spread Spectrum
Spread Spectrum
Applications of Watermarking

    Rights management

    Contents management

    Access/copy control

    Authentication
    Features of Watermarking
   Invisible/Inaudible
       Information is embedded without digital content
        degradation, because of the level of embedding operation is
        too small for human to notice the change.
   Inseparable
       The embedded information can survive after some
        processing, compression and format transformation.
   Unchanging data file size
       Data size of the media is not changed before and after
        embedding operation because information is embedded
        directly into the media.
Technical Requirements for


  Robustness                  Capacity
    Digital Watermarking Alliance
Represents applications and solutions for:

   Audio and Music Content

   Video, Movies and TV Content

   Digital Imagery

   Identity Documents

   Value Documents
Digital Watermarking
  Alliance Members
Digital Watermarking Examples

   Copyright Communication
       Copy Protection
       Monitoring
       Filtering/Classification
       Authentication/Integrity
   Product Serialization & Tracking
       Asset/Content Management
       Rights Management
       Remote Triggering
       Linking/E-Commerce
  Potential Usage Models and
User Software              Usage Models

                             Copyright Communication
                             P2P systems only distribute non-copyright content
    Detect Copyright DWM
                             Licensed Content
       Detect Content ID     P2P systems can resell copyrighted content with license
                             agreements with content owners

                             Enhanced Content
                             P2P systems provide or sell media content information
                             and related items
Copyright Digital Watermark
Content Owner                           User’s PC

  Audio/Video Master                     Rip Software             User Software
  Embed Copyright                        Compressed Audio/Video   Detect Copyright and Content ID
  and Content ID DWM                     File (e.g. MP3 file)     DWM for Secure and Enhanced

                       Rights & Info Database
                       Content ID linked to rights,
                       information and related content
                                                                  Provider Index Database Location
                                                                  (Centralized or Distributed)

Can be used to address P2P and social network content Identification
needs as well as providing identification of orphan works and access to
                   metadata/networked information
         Filtering & Classification

                                                          Copyrighted       Access Legitimate
                                                                            Copy or License

                                         Content Filter

   Can support existing, established and/or new Classification Systems or content
    identifiers such as MPAA film ratings, ISAN or ad identification codes, etc.

   Filtering can occur at the whole content level and/or at a more granular level
    identifying copyrighted, sensitive and/or questionable material for the given

   May be key element of identifying copyrighted content to support legitimate P2P
        Connected Content/Linking
   Promoting & Facilitating M-Commerce

   Location based services
                                     Captured CD e-logo links to
                                       web and music downloads
   Multimedia access
       Streaming audio
       Music
       Multimedia
       Bookmarking
                                   Ring tones
                                   Buy
                                   Reviews
                                   Tour dates
                                   Samples
                                   Band info
    Digital Media Serialization &
   Identifies content owners and rights while communicating copyright information
   Awareness of watermarked content by consumer creates deterrent against
    unauthorized copying and distribution
   Provides accurate identification of source of unauthorized content discovered on
    the Internet and/or physical media
        Retail Content                                                    Recordable Media

                                   Embed                     Embed
                                 Serial # (1)              Serial # (2)

                                 Content ID

                                                                          (1) At Point of Distribution
                     Content Provider                                     (2) At point of copying/re-distribution

                    Track and take
                    proper action
                                           Serial Number
                         Protected for
Multimedia Security
   Part II: Encryption

              Subrata Acharya
            CS 2310, Spring 2007
   Person authentication
       Assurance that the communicating entity is the one claimed
   Access control
       Prevention of unauthorized use of a resource
   Data confidentiality
       Protection of data from unauthorized disclosure
   Data integrity
       Assurance that data received is as sent
   Non-repudiation
       Protection against denial by the parties in a communication
             Multimedia Data
What separates multimedia data from traditional
 alpha numeric data?
   Large in file size

     May require real-time processing (especially
      for continuous media)

     Portable and mobile applications
Multimedia Encryption Approach
     Signal scrambling
         Historical approach
         Not compatible with modern multimedia compression
         Fast speed but low security
     Total encryption with cryptographic ciphers
         Trivial solution
         High security but slow speed
     Selective encryption
         Most popular approach today
         Limited in its range of application
     Integrating encryption into entropy coding
         Complementary to selective encryption
         Very fast computation speed
          Selective Encryption
   Select the most important coefficients and then encrypt them
    with traditional ciphers such as DES

                                Media                       Coefficient                     Cryptographic
                 Digitized                  Coefficients                     Selected
                Audiovisual     System                                      Coefficients
                                                             Selection                         Cipher


                                                                Transmission channel or storage media

   Advantages
       Lower complexity
       High security level provided by traditional cryptology
       Less error correction coding redundancy
       Compatible with existing software and hardware modules
       Example: Selective Encryption
        for G.723.1 Speech Coder
       ITU-T Recommendation G.723.1
                   A popular low bit rate speech codec
       Based on the human voice generation model
                   Vocoder
                   Decoder synthesizes speech using the model

                                     LSP codebook indices        LSP                LSP
                    Vocal Tract
                     Linear filter
                                                               Decoder          Interpolator

                                     Lag of pitch predictors    Pitch               Pitch      Synthesis    Formant
                                          Gain vectors         Decoder            Postfilter     Filter    Postfilter

                                      Fixed codebook gains     Excitation
                                            and others          Decoder
    Vocal Cord                                                                                              Unit
Excitation signal
        Randomized Huffman Table
    0           1                                      0           1
                        1                                                  0
            0                                                  1
A                       0             1            A                                   1
        0   1                                              0   1
                    0       1      0      1                            0       1   1       0
    B       C                                          B       C
                    D       E     F       G                            D       E   F       G

Huffman code #0                 isomorphic tree!       Huffman code #1



     Multimedia Encryption with
     Randomized Entropy Coder
   Select a good PRBG
   Select an r-bit random seed s (encryption key)
   Pseudo-random sequence output from PRBG(s) becomes
    the key hoping sequence (KHS)

    Input                                    1110 1011110
    symbol                                   110001…

       s                         KHS = 011000110 …
   Real time constraint

   Potential cost constraint

   Potential bit rate increase

   Rate variation challenge

   Dynamic network conditions

   Transcoding challenge
   Multimedia security relevance

   Tradeoff approach based on application

   Goal is the design of an
       efficient,
       secure and
       cost effective technique for multimedia security
        using digital watermarking and encryption
Thank you !!!

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