Information Hiding
Soldatov Nikolay
St. Petersburg State University
Joint Advanced Student School ’05
The Introduction

What is that all
about?
Year
1992
1993
1994
1994
1996
1997
1998
Publications
2
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4
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29
64
103
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Use Cases
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Copyright
Military and intelligence agencies
Law enforcement and counter intelligence
agencies
Anonymous communications on the Internet
Digital elections and digital cash
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Road-map
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A basic theory of Steganography
Robust marking systems
Classification of information hiding techniques
Steganographic techniques
Known attacks
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A Basic Theory of Steganography
Steganography:=concealing the very existence of
information transfer

Early results
 Robust marking systems
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Early Results

‘Prisoners’ problem’ (G. J. Simmons in 1983)
The ‘subliminal channel’
B
A
W
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Robust Marking Systems

Not degrade the quality
 Detecting requires secret knowledge ( stegokey )
 Not to interfere
 Survive attacks
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Types of Robust Marking Systems
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Private marking
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Type l: Extract the mark
 Type ll: ‘YES’/’NO’
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Public marking
 Asymmetric marking
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Steganographic Systems
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JSteg (JSteg-shell), JPHide, OutGuess
 SecureEngine
 Stegdetect
 Stegbreak
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Classification Of Information Hiding Techniques
Information Hiding
Covet Channels
Steganography
Linguistic Steganography
Anonymity
Technical Steganography
Copyright Marking
Robust Copyright Marking
Fragile Watermarking
Watermarking
Imperceptible watermarking
Visible Watermarking
Fingerprinting
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Watermark Embedding Scheme
Mark
Stego
image
Marking
Algorithm
Marked image
Secret/public key
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Watermark Recovery Scheme
Mark and/or original
image
Test
image
Detection
Algorithm
Mark or
confident
message
Secret/public key
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One of The Oldest Watermark
Monograms figuring
TGE RG (Thomas
Goodrich Eliensis/
Remigius Guedon)
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Steganographic Techniques
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Security through obscurity
Camouflage
Hiding the location
Spreading the information
Specific techniques
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Security Through Obscurity
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Music scores (Gaspar Schott: Schola
Steganographica)
Geometric drawing (John Wilkins)
Acrostic (David Kahn. The Codebreakers)
Semagrams
Embed additional data in the last significant
bits
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Camouflage
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Anamorphic images (‘Vexierbird’ by Shö)
‘Shaved slave’ (Histiaeus, around 440 B.C.,
but still was used in the 20th century!)
Needle or invisible ink dots (are in use in
document security)
Photographic reduction
Masking algorithms (MPEG, buried data
channels)
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Masking Algorithms (Scheme)
Key
Mark
Transform
space
Inverse
transform
space
Marked
signal
Perceptual
analysis
Signal
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Transform
space
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Hiding The Location of Hidden Information
Paper mask (Ancient China – a British bank
(1992))
 Mathematical tables (XVII-XVIII)
 Format features of electronic published
documents
 Errors in randomly chosen last significant bits

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Spread The Hidden Information
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Patchwork
Spread spectrum systems
Discrete cosine transform ( W·W´/ √(W´·W´) )
MP3Stego etc.
Echo hiding
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Information Hiding in JPEG Images (DCT)

Discrete cosine
transform (DCT)
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Techniques Specific to The Environment

Meteor burst communication
 Ultra-violet fluorescent inks
 Optical variable devices combined with hardreproducible overt marks
 Covert channels
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Known Attacks
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Jitter attacks
Robustness attacks
Attack on echo hiding
The mosaic attack
Interpretation attacks
Implementation
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Jitter Attacks
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Timing errors
 Change the length of a musical performance
(Hamdy et. al. “Timescale modifications of
audio signals with combined harmonic and
wavelet representations”)
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Robustness Attacks

Stir Mark. Applies a minor unnoticeable geometric distortion, like
low frequency deviation, small and smoothly distributed error in
all values, stretching, rotation etc.
General lesson: given a target marking scheme,
one can invent a distortion that will prevent
detection of the watermark leaving the
perceptual quality undiminished
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‘Lena’ Before (a) And After (b) Stir Mark
(a)
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(b)
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Grid With The Same Distortion
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Attack on Echo Hiding

Blind echo cancellation (hard problem in
general case)
 Cepstrum analysis
Experiments on random signals show that there
is a method, which returns quite accurate
estimators of the delay, when an artificial echo
has been added to the signal
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The Mosaic Attack
Procedure: based on chopping an image into a
number of smaller subimages
Upgrades: mobile code, purchasing
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Interpretation Attacks

‘Protocol’ level attack (Crawler et al.)
D+W-W´
Counter-attack: time stamping, notarisation
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Implementation Considerations
Attacks, exploiting weaknesses in the
implementation rather than in underlying
marking algorithms
 Impersonate user (password search,
disassembling)
 Changing ID
 Bypass checking of previous watermark
(debugger)
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Statistical Analysis

Universal statistical
test for random bit
generators
 χ2-test
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Examples (Spammimic)
Dear Friend ; We know you are interested in receiving
cutting-edge news . If you are not interested in our
publications and wish to be removed from our lists,
simply do NOT respond and ignore this mail . This mail
is being sent in compliance with Senate bill 1626 ,
Title 3 ; Section 304 ! Thanks! Dear Friend , Especially for you –
this amazing news ! We will comply with all removal
requests . This mail is being sent in compliance with
Senate bill 1618 ; Title 2, Section 301 . This is not multi-level
marketing ! Best regards!
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Examples (base64)
Secret message
-----BEGIN PGP MESSAGE----Charset: ISO-8859-1
Version: GnuPG v1.2.5 (MingW32)
Comment: Using GnuPG with Thunderbird http://enigmail.mozdev.org
U2VjcmV0IG1lc3NhZ2U=
-----END PGP MESSAGE-----
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Examples (base64)
Man is distinguished, not only by his reason, but by this singular passion
from other animals, which is a lust of the mind, that by a perseverance
of delight in the continued and indefatigable generation of knowledge,
exceeds the short vehemence of any carnal pleasure.
TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFz
b24sIGJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhl
ciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRo
YXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUg
Y29udGludWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb
2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2
Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=
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References

Niels Provos, Peter Honeyman. Detecting
steganographic content on the Internet
 Fabien A.P. Petitcolas, Ross J. Anderson,
Marcus G. Kuhn. Information hiding – a survey
 Stefan Katzenbeisser, Fabien A.P. Petitcolas
(editors). Information hiding techniques for
steganography and watermarking
 Special thanks to www.spammimic.com
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