"Steganography - PowerPoint"
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