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					Steganography

  Kati Reiland
     CS 419
   April 7, 2003
    What is Steganography?
• Technically meaning “covered writing”

• Anything that hides information in
  another media without making any
  visible changes to the media.

• Not cryptography
     History of Steganography
•   In 440 b.c. Demeratus warned Sparta
•   Shaved messenger’s head
•   “Invisible Inks”
•   A Beautiful Mind
•   Hidden Data in i’s, j’s, and periods
•   Today, used to protect currency from
    counterfeiting
     Uses of Steganography
• Hiding of information to avoid
  observation or detection
• Protection of intellectual property
  rights.
   Possible Uses of Steganography                     Drawbacks

Used to combine explanatory             Could accidentally degrade or render
information with an image (e.g.         an image misleading
doctor’s notes with an x-ray)
Embedding corrective audio or image     Could counteract with the original
data in case corrosion occurs from a    image
poor transmission or connection
Peer-to-peer private communications     Doesn’t hide the fact that an e-mail
                                        was sent
Posting secret communications on the    Anyone with a cracking tool could
web to avoid transmission               expose and read the message
Copyright protection                    Hardware tools needed to protect the
                                        watermarking.
Maintaining Anonymity                   It is easier to use free web-based e-mail
                                        or cloaked e-mail
Hiding data on the network in case of a Better to understand and effectively
breach                                  use standardized encryption
                                                      Table from ComputerWorld, 2002
        Avoiding Detection
• Binary Data
  – ASCII text
  – Graphics
• Cover Object
• Where is it hidden?
  – TCP/IP Headers
  – Spaces in Text
  – “Noise” in sound files
  – Least Significant Bits in image files
   Example of Hidden Data
• Camouflaging
  – Fishing freshwater bends and saltwater
    coasts rewards anyone feeling stressed.
    Resourceful anglers usually find masterful
    leapers fun and admit swordfish rank
    overwhelming anyday.
Fishing freshwater bends and saltwater coasts
rewards anyone feeling stressed. Resourceful
anglers usually find masterful leapers fun and
admit swordfish rank overwhelming anyday.
        An Easier Example
• After the theater, all clients keep a tab
  down at Wesley’s Nook.

After the theater, all clients keep a tab
down at Wesley’s Nook.


         ATTACK AT DAWN
           Data in Audio
• Uses Least Significant Bits to hold data
• May retain data in the “unhearable”
  areas of the audio file
            Data in Images
• Large files offer the best option for
  concealment but they are also the most
  difficult to transmit.
  – Compression
     • Lossless
     • Lossy
• 3 Types of Hiding in Digital Images
  – Least Significant Bit (LSB) Insertion
  – Masking and Filtering
  – Algorithms and Transformations
From Protecting Personal Data
Various Color Palettes
             LSB Insertion
•   Can be destroyed by any compression
•   On average, only alters 50% of the bits
•   Works best with 24-bit cover images
•   Undetectable to the human eye
From Protecting Personal Data
     Masking and Filtering
• Used for 24-bit and Gray-
  scale images
• “Watermarking”
• Extend the image to
  include the information as
  a part of the cover image.
• Generally unchanged by
  compression
Algorithms and Transformations
• Discrete Cosine Transform
  – A lossy compression (cosines are not exact
    calculations)
• Redundant Pattern Encoding
  – Also called Spread Spectrum Methods
  – Scatters info in the image and “marks” the
    significant areas
  – The rules for scattering and swapping are
    kept by the “stego-key”
   Most Popular Stego Tools
• StegoDos

• White Noise Storm

• S-Tools

• Hide and Seek
       Protection of Rights
• Digital Watermarking

• Digital Fingerprinting
                   Uses
• Copyright Information
  – Integrity
  – Informs of Ownership
• Stop Piracy
  – Ruins the use of pirated software, music, or
    data
  – Simply doesn’t allow duplicates to be made
• Keep track of where the music/software
  is being used
     Digital Watermarking
• Places a piece of information, usually
  copyright information about the owner,
  repeated within the data.
• MagicGate and OpenMG
• MP3Stego
• PictureMarc
     Digital Fingerprinting
• An embedded unique pattern into each
  distributed copy of the data.

• The unique data needs to appear
  normal to the user.
            Steganalysis
• The process of finding hidden data in
  other media.
• Corporate Data Theft
• 4 Types of Attacks
  – Stego-only Attack
  – Chosen Stego Attack
  – Known Cover Attack
  – Known Stego Attack
                 Bibliography
The Code Book by Simon Singh

Steganography and Steganalysis by Joshua Silman

Steganography by Neil Johnson

Steganography: The New Terrorist Tool? By Danley
  Harrison

TechTV’s various articles on Copy Protection and Digital
  Watermarking

Protecting Personal Data by Simone Fischer-Hubner

				
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