Survey of steganography - University of Florida

Survey of steganography - University of Florida

SURVEY OF STEGANOGRAPHY With an emphasis on audio techniques. By: Eric Hernandez DISCUSSION OVERVIEW What is steganography? Definition Dos/Donts Steganographic techniques Images Audio Other

applications Steganalysis Overview Specific audio example Examples of use in the real world WHAT IS STEGANOGRAPHY? Literally, covered writing Invisible inks Character arrangement (non-cryptographic)

Wax coverings Formal Definition: Steganography is the technique of concealing information within seemingly innocuous carriers. It is the art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message. RULES OF STEGANOGRAPHY 1. Strength is not stealth Stegonography =/= Cryptography Not exclusive 2.

Assume the hiding method is known 3. 4. Known as Kerchkoffs principle in crypto Never divulge side information Dont add noise to a where it doesnt belong Cover images Audio STEGANOGRAPHIC TECHNIQUES STEGANOGRAPHIC TECHNIQUES: IMAGES

Common approaches: LSB modification Masking Filtering Transformations via algorithms Not all approaches created equal Size restrictions Vulnerability to manipulation STEGANOGRAPHIC TECHNIQUES: IMAGES, LSB Composed of hiding information inside of the LSB of an image Leads to a few requirements:

Image must have suitable noise Image must be of sufficient size Must be able to hide in plain sight Advantages/Disadvantages Easy to implement Does not stand up to compression Scalability STEGANOGRAPHIC TECHNIQUES: IMAGES, MASKING AND FILTERING Most commonly seen as watermarks as a

mean to protect copyright Not traditional steganography in that information is being extended, not hidden Accomplished not by hiding in noise, but by manipulating luminescence Changes visible properties of an image, but can be still made to be undetectable to the human eye Advantages/Disadvantages More

suitable for lossy compression than LSB Not traditional stego STEGANOGRAPHIC TECHNIQUES: IMAGES, ALGOS AND TRANS Based on transformation via formula Discrete Cosine Transformation (DCT) Fast Fourier Transform Advantages/Disadvantages Can be visually undetectable Can scatter secret information across image Can be used together with encoding and similar watermarking (luminescence techniques)

Not as susceptible to cropping, compression, etc. Complex STEGANOGRAPHIC TECHNIQUES: AUDIO Human Auditory System (HAS) has a large dynamic range that it can listen through Perceives over a range of power > 1,000,000:1 Range of frequencies > 1,000:1 Makes it hard to add remove data from original sources HAS has a weakness, though: sound differentiation Loud

vs. Soft Several ways to exploit this weakness STEGANOGRAPHIC TECHNIQUES: AUDIO 1. Low-bit encoding Similar to previously discussed LSB stego Easy to use, weak to any changes in audio 2. Phase encoding Substitutes the phase of an initial audio segment with a reference phase that represents the hidden data

Inaudible in terms of signal-to-perceived noise ratio Low data transmission rate Best if used for watermarks or similar small data STEGANOGRAPHIC TECHNIQUES: AUDIO 3. Spread spectrum Spreads secret information across frequency spectrum Two schemes

High level of robustness against removal Possibility of introducing noise 4. Direct Sequence Frequency-hopping Echo Hiding Blends information by introducing echo Vary amplitude, decay rate, offset (delay time) of echo High level of robustness

Echoes mimic environmental conditions (lossy compress.) STEGANOGRAPHIC TECHNIQUES: AUDIO, LSB Can be augmented with pseudorandom number generator to scatter information over audio file. STEGANOGRAPHIC TECHNIQUES: AUDIO, PHASE ENCODING Encodes message as phase shifts in the phase spectrum of a digital signal.

Relies on the fact that phase components of sound are not as perceptible as noise is Steps: 1. Break signal into smaller segments 2. Discrete Fourier Transform (DFT) 3. Phase diff. between adjacent segments 4. Insert message into phase vector of first signal segment only

5. New phase matrix created from new phase of first segment and the original phase difference 6. Use inverse DFT and concatenate segments back together STEGANOGRAPHIC TECHNIQUES: AUDIO, SPREAD SPECTRUM Spreads secret information across the audio signals frequency spectrum Direct-sequence SS Message is spread out by a

constant called the chip rate. Modulated with a pseudorandom signal Interleaved with cover Frequency-hopping SS Audio files frequency spectrum is altered so that it hops randomly between frequencies STEGANOGRAPHIC TECHNIQUES: AUDIO, ECHO HIDING Vary 3 characteristics of

introduced echo Amplitude Decay rate Offset (delay time) Different vary times refer to different bit input So small that humans dont notice STEGANOGRAPHIC TECHNIQUES: AUDIO, ECHO HIDING Break audio into segments Message to be

inserted is Hey After code runs, recombine segments into final signal Creates a noticeable mix of echoes, increasing chance of detection init(Block blocks[]) { for (int i=0; i < blocks.length; i++) { if (blocks[i].echoValue() == 0) blocks[i] = offset0(blocks[i]); else blocks[i] = offset1(blocks[i]); } }Block offset0(Block block) { return (block + (block - OFFSET_0)); }

Block offset1(Block block) { return (block + (block - OFFSET_1)); } STEGANOGRAPHIC TECHNIQUES: AUDIO, ECHO HIDING Create two mixer signals Zero mixer One mixer Less abrupt than before Signals are compliments of each other Ramp ups and downs help with smooth transitions

between echoes Recovery Break signal into same block sequence Autocorrelation function of the signals cepstrum Reveals a spike at each echo time offset STEGANOGRAPHIC TECHNIQUES: OTHER APPLICATIONS Text steganography Little

noise in text to hide information in, but possibilities still exist: Since everyone can read, encoding text in neutral sentences is doubtfully effective. Line number/character number Vertical letter shifts Font changes (make some bs, ds, ps longer than others) Video steganography Combines ideas of both image and audio stego Open systems environment steganography TCP/IP

Containers STEGANALYSIS STEGANALYSIS: OVERVIEW Detect Difficult Need to understand technique in use Involves statistical analysis Especially difficult when Kerckhoffs principle is applied Defeat

Easy No understanding required No statistical analysis required As techniques evolve, will become more difficult STEGANALYSIS: TEXT Detect Defeat Patterns being disturbed

Inappropriate (odd) use of language Line height and white space Difficult when secret key (outside text) is used Rewrite Change spacing, punctuation Modify line heights or layout Add or remove words

Does not work on public cover source Key must be intercepted STEGANALYSIS: IMAGES Detect Defeat Changes in: size File format Last modified time stamp

Color palette File Statistical analysis Examine the LSB Compress using lossy compression Destroys LSB modification

Alter image: Resize Modify color palette Conversion to different file format Luminescence STEGANALYSIS: AUDIO Detect Statistical analysis Similar to images, look at LSB

Examine inaudible frequencies Patterns in background noise Distortions Defeat Similar to images Compression special note: Removes frequencies that cannot be heard (a hideout for some stego)

Lower bitrate Less available space to store stego = at least some data loss STEGANALYSIS: HAUSDORFF DISTANCE Calculation of Hausdorff distance between lines X and Y USES IN THE REAL WORLD STEGANOGRAPHY: USES Copyright Watermarks


A Detailed look at Steganographic Techniques and their use in an Open-Systems Environment tailed-steganographic-techniques-open-systems-environ ment_677 Exploring Steganography: Seeing the Unseen by Neil F. Johnson, Sushil Jajodia Steganography and Steganalysis by J.R. Krenn

Steganalysis: The Investigation of Hidden Information by Neil F. Johnson, Sushil Jajodia Echo Hiding by Daniel Gruhl, Anthony Lu, Walter Bender RESOURCES A Novel Audio Steganalysis Based on HighOrder Statistics of a Distortion Measure with Hausdorff Distance by Yali Liu, others cy_ISC08.pdf

Methods of Audio Steganography thods.html#phase Secret Code in Color Printers Lets Government Track You Hausdorff Distance

Recently Viewed Presentations

  • Processing and Characterization of Piezoelectric Materials into MicroElectroMechanical

    Processing and Characterization of Piezoelectric Materials into MicroElectroMechanical

    Click to edit company slogan . ... (MEMS) denote systems that include one or more small microstructures (sub- μm to mm) that often are fabricated using a technology μnamed micromachining, and materials,that originates partly from the semiconductor industry's processes and...
  • Indicators of Health and Wellbeing in the Early

    Indicators of Health and Wellbeing in the Early

    Arial Wingdings Default Design Slide 1 The ScotPHO Children & Young People Profiles National vs local data Early years indicators Local data = local variation Early years indicators: related work Early years indicators: gaps in local data Early years indicators:...
  • Comprehensive Plan Update Todays Agenda 1. Welcome 2.

    Comprehensive Plan Update Todays Agenda 1. Welcome 2.

    The City Center includes a new Fulton County Library, 5-acre public park, town square and 450- space parking garage. The City Center project will result in a Main Street-styled, village-scaled district that will activate the east side of Main Street...
  • Table of Authorities

    Table of Authorities

    Table of Authorities is a KeyCite related service which includes KeyCite symbols. Access the Table of Authorities service by clicking the Table of Authorities link on the Link for tab in the left frame. Although the Nieminen case does not...
  • Searching alternative sources Document discovery in integrated care

    Searching alternative sources Document discovery in integrated care

    Supporting people to be independent - care in your own home / services/technology. Avoiding unplanned admissions - e.g. falls - Channel shift. Every service in the NHS has nationally set priorities, targets and budget constraints, etc. Increasingly, solutions are looking...
  • The Discovery of Atoms and The Development of

    The Discovery of Atoms and The Development of

    Tin Oxide(s) 100g. tin + 13.5g. oxygen 113.5g. stannous. oxide. stannum = tin (Sn) + 27g. oxygen 127g. stannic. oxide. 100g. tin. SnO. SnO. 2
  • Special Indices for LaaLaLaa Lyric Analysis &amp; Generation ...

    Special Indices for LaaLaLaa Lyric Analysis & Generation ...

    Background LaaLaLaa (Sowmiya, Karky (2010)) talks of splitting raw text from midi file to templates and filling them with words from a wordnet according to the pattern mined from an existing corpus of lyrics with due consideration to rhyme, meaning...
  • Success Stories Template

    Success Stories Template

    Off Premise Icon Wine Push Program. Date & Location: Sept - Oct 2013 / Off Premise Retailers and Fine Wine Shops. Action: Set target list for accounts and designated tasting days with key sale representatives to maximize wine samples