Transcript Chap1

STEGANOGRAPHY:
Information Hiding
SOUNDARARAJAN EZEKIEL
Department of Computer Science
Indiana University of Pennsylvania
Indiana, PA 15705
WELCOME AND THANKS
I
welcome Every One
 I would like to Thank
–Dean
–Chair
–Dr. Micco
–Colleagues
–Students
Why do I want to talk about Steganography
Information
Security undergone two major changes
Computer Security
Protect data
Olden days– filing
cabinet
With a combination
locks for storing
sensitive document
Modern days:- With
introduction of the
computer – protecting
files is important
Example:- virus,
Network Security
Distributed system– use of network—
Communication facilities– carrying
Data between –
Measure needed to protect
data
Source
interruption
modification
Normal
Destination
interception
fabrication
Why do I want to talk about Steg ?
Digital Information revolution changed our
lives– generated new challenges and
opportunities.
 Software, digital camera, MP3 player, PDA
(personal digital assistant) have attracted
consumers worldwide– create, manipulate,
and enjoy multimedia data
 Internet and wireless network—deliver and
exchange information
 Security and fair use of data are important
yet challenging topics

Why do I want to talk about Steg ?
Solutions to these problems help us to
understand the fast moving technology
 I am going to talk about the issues
regarding multimedia information hiding
and its applications in multimedia security
and communications
 Different names:
– Steganography
– Data hiding
– Information hiding
– Digital watermarking
What is the difference between
Steganography and Cryptography
Art of hiding
information
in ways that prevent
the detection of
hidden message
Existence is not
know
Science of writing in
secret code
It encodes a message so
it cannot be understood
Cryptography
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Cipher- Cryptosystem– Encrypt
Map S------- T
Plain text –--- Cipher text
K– enciphering key
Decipher/decrypt—decoding----inverse
Deciphering key k’
k=k’ or k’ is computable from k– symmetric, single key, secret key
K!=k’ or k’ is very hard to derive from k then k’= asymmetric, two key,
public key
Type of operation– keys– plain text processing
Cryptography– study of concealing information, using mathematical
transformation– cryptographer
Cryptanalysis– revealing information hidden by cryptography using
analytical or mathematical analysis
Intelligence– spying the system, stealing decryption, brining
cryptographer, injecting him with truth serum, pointing light/gun in
his face, bashing him over the head with bricks, other tactics
Example : Encrypt.exe
An Illustration of a bucket array
0
1
2
3
4
The bucket for item 6 with
Key=6
5
6
7
8
Arbitrary Objects
Hash code
-3 -2 -1
0
1
2
3
Compression map
0
1
2
3
….
N-1
The two parts of a hash functions: a hash code and a
compression map
TITLE Encryption Program
INCLUDE Irvine32.inc
KEY = 239
BUFMAX = 128
.data
sPrompt BYTE "Enter the plain text: ",0
sEncrypt BYTE "Cipher text:
",0
sDecrypt BYTE "Decrypted:
",0
buffer BYTE BUFMAX dup(0)
bufSize DWORD ?
.code
main PROC
call InputTheString
call TranslateBuffer
mov edx,OFFSET sEncrypt
call DisplayMessage
call TranslateBuffer
mov edx,OFFSET sDecrypt
call DisplayMessage
exit
main ENDP
InputTheString PROC
pushad
mov edx,offset sPrompt
call WriteString
mov ecx,BUFMAX
mov edx,offset buffer
mov bufSize,eax
call Crlf
popad
ret
InputTheString ENDP
DisplayMessage PROC
pushad
call WriteString
mov edx,offset buffer
call WriteString
call Crlf
call Crlf
popad
ret
DisplayMessage ENDP
TranslateBuffer PROC
pushad
mov ecx,bufSize
mov esi,0
L1:xor buffer[esi],KEY
inc esi
loop L1
popad
ret
TranslateBuffer ENDP
END main
Steganography-- History
Greek origin --  ,    meaning “ covered
writing”
 History goes back to BC 400
 Herodotus ( c486-425 B.C.) tells around 400BC how
Histiaeus shaved the head of his most trusted slave and
tattooed it with a message which disappeared after the
hair had re-grown– purpose was to instigate a revolt
against the Persians
 Message written on table– waxed, painted
 Notes carried by pigeons
 Invisible ink– milk or urine – use heat to see
 Small holes above or below letters– see with light
 1860’s– images are used to hide information
 During WWI– Father is dead– modified as Father
deceased--- Reply telegram went – Is Father dead or
deceased?
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Fishing freshwater bends and saltwater coasts rewards
anyone feeling stressed. Resourceful anglers usually find
masterful leapers fun and admit swordfish rank
overwhelming anyday.
 Send Lawyers, Guns, and Money
 Apparently neutral's protest is thoroughly discounted and
ignored. Isman hard hit. Blockade issue affects pretext for
embargo on by-products, ejecting suets and vegetable oils.
 Pershing sails from NY June 1
 We explore new steganographic and cryptographic
algorithms and techniques throughout the word to produce
wide variety and security in the electronic web called the
Internet.
 We explore new steganographic and cryptographic
algorithms and techniques throughout the word to produce
wide variety and security in the electronic web called the
Internet.
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EXPLORE THE WORLD WIDE WEB
Steganography– Methods-- Category
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Embedded data is called Watermark(s)
Data Hiding Techniques
Perceptual
Sources
Audio,
Images,
Video,
3-D Graphics
Lossy Compression
Non Perceptual
sources
Text
Executable codes
Lossless Processing
Application Domain
Ownership Protection:
Ownership is embedded in
the media
Authentication or Tempering Detection:-
Set of secondary data embedded to determine the host media
is tampered or not--- Blind detection
Fingerprinting or Labeling
Used to trace the originator or recipients of a particular copy of multimedia copy
Copy Control or Access Control
Copy control access control policy– DVD copy control or
SMDI activities
Annotations:- Convey any message– no
robustness
Steganography of today’s talk
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The steganography of today’s talk is about digital
images ( video, audio) as mediums
Stegokey
Password
Stego-Meida
Cover Media
( Carrier)
Message
to Hide
Steganography
Application
Carrier with the
Hidden message
Cover medium+ embedded message+stegokey== stego-medium
Cover image
Embedding
Function
Extracting
Function
Stego
101011101011
101011101011
101100100100
101100100100
100011010111
100011010111
101011101011
101011101011
101100100100
101100100100
100011010111
100011010111
Message to embedded
Extracted Message
Lets Talk about Image
X0(100,100)= ( 237, 211,214)—RGB
=( 11101101, 11010011, 11010110)
Color– V I B G Y O R
Binary Image–
two color
Gray Image–
Color Image
Pixel– Pixel Element
X(100,100)=219
11011011
380 NM -- 780 NM
FREQUENCEY – 370-750 trillion HZ
Speed= 300,000 km/sec
Wavelength= speed/ freq
Steganography Methods
Lets us discuss few methods and its
advantage and disadvantage
 1. Least Significant Method
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– Idea:- Hide the hidden message in LSB of the
pixels
– Example:– Advantage:- quick and easy– works well in
gray image
– Disadvantage:- insert in 8 bit– changes color–
noticeable change– vulnerable to image
processing– cropping and compression
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Redundant method
– Store more than one time--- withstand
cropping
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Spread Spectrum
– Store the hidden message everywhere
STEGANALYSIS
 Detection
Distortion
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Analyst observe various
Various relationship between
Cover, message, stego-media
Steganography tool
Seeing the Unseen
Analyst manipulate the stego-media
To render the embedded information
Useless or remove it altogether
DCT - Discrete Cosine Transformation
– Encode
• Take image
• Divide into 8x8 blocks
• Apply 2-D DCT--- DCT
coefficients
• Apply threshold value
• Store the hidden message
in that place
• Take inverse– store as
image
1720
– Decode
• Start with modified image
• Apply DCT
• Find coefficient less than
T
• Extract bits
• Combine bits and make
message
1.524
5.667
3.475
0.3711 -1.442
3.888 -3.356
1.625 -2.279
-4.049 -1.223
1.876
1.924
0.8995 -0.7233
219
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218 215 211 211 213 214 216 216
7.683
-4.181
1.067
-1.97
0.4735
0.5466
-1.369
0.667
1.234
1.625 0.9234 -0.07047 -1.055
-1.524
1.152
1.637
1.016 0.3802
5.944 0.3943 -0.4591 0.1313 0.7812
3.265 0.5632 -0.939 -0.2434 0.2354
1.392
1.375 0.6552 -1.143 0.03459
-0.5425 -1.013 -0.2651 0.5696 -0.9296
-1.132 -0.02802 -0.4646 0.1831 0.9729
0.436 0.1325 -0.03665 -0.3141 -0.4749
Wavelets Transformation
Wavelets are basis function wjk (t ) in continuous time.
a basis is a set of linearly independent functions that can be used
to produce all admissible functions f(t)
f (t )  combination of basis functions  bjk wjk (t )
j ,k
The special feature of wavelet basis is that all functions wjk (t )
are constructed from a single mother wavelet w(t). This wavelet is
is a small wave ( a pulse). Normally it starts at time t=0 and end at
time t=N
j
w0k (t )  w(t  k )
Shifted
k
time
=
w

w
(2
t
)
j
0
Compressed =
Combine both we have wjk (t )  w(2 j t  k )
Haar Wavelet :- 1909 Haar, 1984– theory, 88– daubechies
Haar=
89- Mallat 2-d, mra, -- 92- bi-orthogonal
Carrier
Stego image
Wavelet
Transformation
Thresholding
Compression
Message to be Hidden
Error Image
Inverse Transformation
Extract the Hidden Message
Discussion
Noise – we are running into a problem
 RMS( Root Mean Square Error)
 PSNR( Peak-Signal-to-Noise- Ratio)
5- 42, 10-37, 20-34, ….. 60- 29
 Future Work:- Explore hiding information
in detail coefficients
 Combine:- Cryptography with
Steganography
 Check for Robustness--- ( Attacks–
Processing, modifying….)
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