Multimedia Security Part I Digital Watermarking Subrata Acharya

Multimedia Security Part I: Digital Watermarking Subrata Acharya CS 2310, Spring 2007

Digital Watermarking? n n Allows users to embed some data into digital contents 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 n Visible n n A visible translucent image which is overlaid on the primary image Invisible n An overlaid image which cannot be seen, but which can be detected algorithmically

Visible Watermark n n 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 organization. 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 n n n Embedding level is too small to notice Can be retrieved by extraction software Applications: n n n Authentication Copyrighting Etc…

Invisible Watermark

Embedding Techniques n Spatial domain n Frequency domain n Original needed Original not needed Spread domain

Spatial Domain

Frequency Domain n Watermarking signal to embed n Host signal n Frequency components n Embedding n Extraction

Frequency Domain

Spread Spectrum

Spread Spectrum

Applications of Watermarking n Rights management n Contents management n Access/copy control n Authentication

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

Technical Requirements for Watermarking Invisibility Robustness Capacity

Digital Watermarking Alliance Represents applications and solutions for: n Audio and Music Content n Video, Movies and TV Content n Digital Imagery n Identity Documents n Value Documents

Digital Watermarking Alliance Members

Digital Watermarking Examples n Copyright Communication n n Copy Protection Monitoring Filtering/Classification Authentication/Integrity Product Serialization & Tracking n n Asset/Content Management Rights Management Remote Triggering Linking/E-Commerce

Potential Usage Models and Benefits User Software Usage Models Copyright Communication P 2 P systems only distribute non-copyright content Detect Copyright DWM Licensed Content Detect Content ID P 2 P systems can resell copyrighted content with license agreements with content owners Enhanced Content P 2 P systems provide or sell media content information and related items

Copyright Digital Watermark Architecture Content Owner Audio/Video Master Embed Copyright and Content ID DWM User’s PC Rip Software Compressed Audio/Video File (e. g. MP 3 file) User Software Detect Copyright and Content ID DWM for Secure and Enhanced content Rights & Info Database Content ID linked to rights, information and related content Provider Index Database Location (Centralized or Distributed) Can be used to address P 2 P 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 Non-Copyrighted Content Filter n n n 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 audience May be key element of identifying copyrighted content to support legitimate P 2 P distribution

Connected Content/Linking n Promoting & Facilitating M-Commerce n Location based services n Multimedia access n n Captured CD e-logo links to web and music downloads Streaming audio Music Multimedia Bookmarking DOWNLOAD § Ring tones § Buy tickets § Reviews § Tour dates § Samples § Band info

Digital Media Serialization & Tracking n n n 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 Serial # (1) Embed Serial # (2) Content ID (1) At Point of Distribution Content Provider Track and take proper action Protected for privacy (2) At point of copying/re-distribution Detect Serial Number

Multimedia Security Part II: Encryption Subrata Acharya CS 2310, Spring 2007

Goals n Person authentication n n Access control n n Protection of data from unauthorized disclosure Data integrity n n Prevention of unauthorized use of a resource Data confidentiality n n Assurance that the communicating entity is the one claimed Assurance that data received is as sent Non-repudiation n Protection against denial by the parties in a communication

Multimedia Data What separates multimedia data from traditional alpha numeric data? n Large in file size n n May require real-time processing (especially for continuous media) Portable and mobile applications

Multimedia Encryption Approach n Signal scrambling n n Total encryption with cryptographic ciphers n n n Trivial solution High security but slow speed Selective encryption n Historical approach Not compatible with modern multimedia compression Fast speed but low security Most popular approach today Limited in its range of application Integrating encryption into entropy coding n n Complementary to selective encryption Very fast computation speed

Selective Encryption n Select the most important coefficients and then encrypt them with traditional ciphers such as DES Digitized Audiovisual data Media Compression System Coefficients Coefficient Selection Nonselected Coefficients Selected Coefficients Cryptographic Cipher Error Correction Coding Transmission channel or storage media n Advantages n n 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 n ITU-T Recommendation G. 723. 1 n n A popular low bit rate speech codec Based on the human voice generation model n n Vocoder Decoder synthesizes speech using the model Vocal Tract Linear filter Vocal Cord Excitation signal generation LSP codebook indices LSP Decoder Lag of pitch predictors Gain vectors Pitch Decoder Fixed codebook gains and others Excitation Decoder LSP Interpolator + Pitch Postfilter Synthesis Filter Formant Postfilter Gain Scaling Unit

Randomized Huffman Table Encryption 1 0 A 0 B C 0 1 D E Huffman code #0 0 0 F 1 G isomorphic tree! 0 0 0 00 0 1 A 1 0 1 1 0 B 0 1 1 D E 1 C F Huffman code #1 1000110010101101111 BADCAEFG 100 110 1 0 11001110110110111111 0 G

Multimedia Encryption with Randomized Entropy Coder n Select a good PRBG n Select an r-bit random seed s (encryption key) n Pseudo-random sequence output from PRBG(s) becomes the key hoping sequence (KHS) Entropy Input symbol s Coder PRBG 1110 1011110 110001… KHS = 011000110 …

Challenges n Real time constraint n Potential cost constraint n Potential bit rate increase n Rate variation challenge n Dynamic network conditions n Transcoding challenge

Conclusion n Multimedia security relevance n Tradeoff approach based on application n Goal is the design of an n efficient, secure and cost effective technique for multimedia security using digital watermarking and encryption

Thank you !!!