Security in Computer System

1. Security in Computer System
491 CS-G(172)
By
Manesh T
maneshpadmayil@gmail.com

2. AGENDA
• Overview of Security & Needs
• Concepts, Types of Viruses
• Different Types of Security
• Threats in Network
• Hacking, Ethical Hacking
• Attacks, services and mechanisms
• Security attacks-Types
• Security services
• Methods of Defense
• A model for Internetwork Security

3. Overview
• What is security?
• Why do we need security?
• Who is vulnerable?

4. What is “Security”
Security is state of having
1. Freedom from risk or danger; safety.
2. Freedom from doubt, anxiety, or fear
Definition:
Security is the protection of assets. Three main
aspects of security are
1. Protection
2. Detection
3. Reaction.

5. Why do we need security?
• Protect vital information while still allowing
access to those who need it
– Trade secrets, medical records, etc.
• Provide authentication and access control
for resources
– Ex: Bank Identity Card, ATM Card
• Guarantee availability of resources
– Must be available all the time

6. Need for Security
• The Information Age- Internet Highway
• Digital Assets- emails, documents
• Static Assets- pictures, databases
• Assets on Transit- emails(Comm. Networks)

7. Who is vulnerable?
• Financial institutions and banks
• Internet service providers
• Pharmaceutical companies
• Government and defense agencies
• Internet users
• Multinational corporations
• ANYONE ON THE NETWORK

8. Different Types of Security-Definitions
• Computer Security - generic name for the
collection of tools designed to protect
hardware or software modules.
• Network Security - measures to protect
data during their transmission
• Internet Security - measures to protect
data during their transmission over a
collection of interconnected network
• Information Security- All the three areas

9. Basic Terminologies
• Cryptography
– Study of mathematical techniques related to aspects of
information security (Set of techniques)
• Cryptanalysis
– The process of breaking the security policies
• Cryptology
- Cryptography + cryptanalysis
• Cryptosystems are computer systems used to encrypt data
for secure transmission and storage

10. Types of Computer Virus
1.Time Bomb
2.Logical Bomb
3.Worm
4.Boot Sector Virus
5.Macros Virus
6.Trojan Horse

11. Types of Viruses
• Time Bomb – Active when time/date comes
• Logical Bomb – Active when some action comes
• Worm- Self replicating in networks
• Boot Sector Virus- During system boot, boot sector virus is
loaded into main memory and destroys data stored in hard disk
• Micro Virus- It is associated with application software like
word and excel
• Trojan Horse- usually email virus

12. Launching the attack
Steps are
1. Vulnerability
2. Threat
3. Discovery of Vulnerability
4. Exploitation of Vulnerability
5. Attack

13. Attacks, Services and Mechanisms
• Security Attack: Any action that compromises the
security of information.
• Security Mechanism: A mechanism that is
designed to detect, prevent, or recover from a security
attack.
• Security Service: A service that enhances the
security of data processing systems and information
transfers. A security service makes use of one or more
security mechanisms.

14. Different Types of Security Attacks

15. Security Attacks
• Interruption: This is an attack on
availability
• Interception: This is an attack on
confidentiality
• Modification: This is an attack on integrity
• Fabrication: This is an attack on
authenticity

16. Security Goals

17. Threats in Networks

18. In This Section
• What makes a network Vulnerable
– Reasons for network attacks
• Who Attacks Networks?
– Who are the attackers? Why people attack?
• Threats in Network transmission:
Eavesdropping and Wiretapping
– Different ways attackers attack a victim

19. What Makes a Network Vulnerable
• How network differ from a stand-alone
environment:
– Anonymity
• Attacker can mount an attack from thousands of
miles away; passes through many hosts
– Many points of attack
• Both targets and origins
• An attack can come from any host to any host
– Sharing
• More users have the potential to access networked
systems than on single computers

20. • How network differ from a stand-alone
environment:
– Complexity of System
• Reliable security is difficult to obtain
• Complex as many users do not know what their computers are
doing at any moment
– Unknown Perimeter
• One host may be a node on two different networks
• Causing uncontrolled groups of possibly malicious users
– Unknown Path
• Can have multiple paths from one host to another.
What Makes a Network Vulnerable

21. Who Attacks Networks
1. Challenge – what would happen if I tried this
approach or technique? Can I defeat this network?
2. Fame
3. Money and Espionage(Spy)
4. Organized Crime
 Ideology
 Hacktivism – breaking into a computer system with the
intent of disrupting normal operations but not causing
serious damage
 Cyberterroism- more dangerous than hacktivism can
cause grave harm such as loss of life or severe economic
damage

22. Ethical Hacking
• Ethics: Moral principles that govern a person's or
group's behavior
• Hacking: Practice of modifying the features of a
system, in order to accomplish a goal outside of the
creator's original purpose
• Ethical Hacking: Process of legally hacking the
information that is considered to be confidential

23. Ethical Hacker Vs Hacker

24. Types of Hackers

25. How attackers perpetrate attacks?
1. Port Scan
For a particular IP address, the program will gather network information.
It tells an attacker which standard ports are being used, which OS is
installed on the target system, & what applications and which versions are
present.
2. Social Engineering
It gives an external picture of the network to the attacker.
3. Operating System & Application Fingerprinting
Determining what commercial application server application is running,
what version…
4. Intelligence
Gathering all the information and making a plan.
e information and making a plan.

26. Threats In Network Transmission
• Eavesdropping
– Overhearing without expending any extra effort
– Causing harm that can occur between a sender
and a receiver
• Wiretapping
– Passive wiretapping
• Similar to eavesdropping
– Active wiretapping
• Injecting something into the communication

27. Wiretapping Communication
 Cable
 Packet sniffer – A device that can retrieve all packets of LAN
 Inductance – a process where an intruder can tap a wire and read
radiated signals without making physical contact with the cable
 Microwave, Wireless
 Signals are broadcasted through air, making more accessible to
hackers
 Signals are not usually shielded or isolated to prevent interception
 Satellite Communication
 Dispersed over a great area than the indented point of reception
 Communications are multiplexed, the risk is small that any one
communication will be interrupted
 Greater potential than microwave signals

28. Wiretap Vulnerabilities
Network Security / G. Steffen 28

29. Threat Categories
 Impersonation
 Easier than wiretapping for obtaining information on a network
 More significant threat in WAN than in LAN
 Spoofing
 An attacker obtains network credentials illegally and carries false
conversations
 Masquerade
 One hosts pretends to be another
 Phishing is a variation of this kind of an attack.
 Session hijacking
 Intercepting & carrying a session begun by another entity
 Man-in-the-Middle Attack
 One entity intrudes between two others.

30. Vulnerability and Attacks
• Exploiting a Vulnerability
• Passive Attacks
• Active Attacks
• Hacking
• Social Engineering
• Identity Theft

31. Passive Attacks

32. Active Attacks

33. Attacks to Security Goals

34. Various Security Attacks
• Brute-force Attack
• Spoofing Attack
• Denial of Service
attack(DoS)
• Distributed DoS
Attack(DDoS)
• Authentication attacks
I. Dictionary Attack
II. Replay Attack-
aquestic attack
III. Password Guessing
IV. Password Sniffing

35. Security Services-Principles of
Information Security
• Security Attributes (CI5A)
– Confidentiality
– Integrity
– Availability
– Authentication
– Authorization
– Accounting
– Anonymity

36. Confidentiality

37. Integrity

38. Availability

39. Authentication

40. Authorization

41. Non-Repudiation

42. Accountability

43. Model for Network Security

44. Methods of Defence
• Encryption
• Software Controls (access limitations in a
data base, in operating system protect each
user from other users)
• Hardware Controls (smartcard)
• Policies (frequent changes of passwords)
• Physical Controls

45. Cryptographic Techniques
Cryptography
Some security services can be implemented using
cryptography. Cryptography, a word with Greek origins,
means “secret writing”.
Steganography
The word steganography, with its origin in Greek, means
“covered writing”, in contrast to cryptography, which means
“secret writing”.

46. Basic Terminology
• plaintext - the original message
• ciphertext - the coded message
• cipher - algorithm for transforming plaintext to
ciphertext
• key - info used in cipher known only to
sender/receiver
• encipher (encrypt) - converting plaintext to
ciphertext
• decipher (decrypt) - recovering ciphertext from
plaintext
• cryptography - study of encryption
principles/methods
• cryptanalysis (code breaking) - the study of
principles/ methods of deciphering ciphertext
without knowing key

47. Basic Terminologies
• Plaintext is text that is in readable form
• Ciphertext results from plaintext by applying the
encryption key
• Notations:
• M = message, C = ciphertext, E = encryption,
D = decryption, k= key
• Encryption
Ek(M)=C
• Decryption
Dk(C)=M

48. Cipher-Algorithm
• Symmetric cipher: same key used for
encryption and decryption
– Block cipher: encrypts a block of plaintext at a
time (typically 64 or 128 bits)
– Stream cipher: encrypts data one bit or one byte at
a time
• Asymmetric cipher: different keys used for
encryption and decryption

49. The general idea of Key based
cryptography

50. Traditional Ciphers
SUBSTITUTION AND TRANSPOSITION.
Substitution ciphers
A substitution cipher replaces one symbol with another.
If the symbols in the plaintext are alphabetic characters,
we replace one character with another.
A substitution cipher replaces one symbol
with another.
The simplest substitution cipher is a shift cipher
(additive cipher).

51. Example
Use the additive cipher with key = 15 to encrypt the message
“hello”.
Solution
We apply the encryption algorithm to the plaintext, character by
character:
The ciphertext is therefore “wtaad”.

52. Transposition ciphers
A transposition cipher does not substitute one symbol for
another, instead it changes the location of the symbols
A transposition cipher reorders symbols.

53. Example
Alice needs to send the message “Enemy attacks tonight” to
Bob. Alice and Bob have agreed to divide the text into groups of
five characters and then permute the characters in each group.
The following shows the grouping after adding a bogus character
(z) at the end to make the last group the same size as the others.
The key used for encryption and decryption is a permutation key,
which shows how the character are permuted. For this message,
assume that Alice and Bob used the following key:

54. Example
The third character in the plaintext block becomes the first
character in the ciphertext block, the first character in the
plaintext block becomes the second character in the ciphertext
block and so on. The permutation yields:
Continued
Alice sends the ciphertext “eemyntaacttkonshitzg” to Bob. Bob
divides the ciphertext into five-character groups and, using the
key in the reverse order, finds the plaintext.

55. Substitution Ciphers
• Mono-alphabetic Cipher- Ceaser Cipher
• Poly- alphabetic Cipher- Vigenere Cipher
• Multiple letter cipher- Playfair cipher

56. Caesar Cipher
• Earliest known substitution cipher
• Invented by Julius Caesar
• Each letter is replaced by the letter three positions
further down the alphabet.
• Plain: a b c d e f g h i j k l m n o p q r s t u v w x y z
Cipher: D E F G H I J K L M N O P Q R S T U V W X Y Z A B C
• Example: ohio state  RKLR VWDWH

57. Caesar Cipher
• Mathematically, map letters to numbers:
a, b, c, ..., x, y, z
0, 1, 2, ..., 23, 24, 25
• Then the general Caesar cipher is:
c = EK(p) = (p + k) mod 26
p = DK(c) = (c – k) mod 26
• Can be generalized with any alphabet.

58. Polyalphabetic Cipher
• In monoalphabetic cipher the problem was
that each character was substituted by a
single character
• Cryptanalysts are helped by the fact that
they have to see what character would
correspond in plaintext for a given
ciphertext character
• Polyalphabetic cipher’s goal is to make this
process difficult

59. Polyalphabetic Cipher
• In polyalphabetic cipher, each plaintext character
may be replaced by more than one character
• Since there are only 26 alphabets this process will
require using a different representation than the
alphabets
• Alphabets ‘A’ through ‘Z’ are replaced by 00, 01,
02, …, 25
• We need two digits in this representation since we
need to know how to reverse the process at the
decryption side

60. 60
Polyalphabetic Cipher
• The most common method used is Vigenère
cipher
• Vigenère cipher starts with a 26 x 26 matrix of
alphabets in sequence. First row starts with ‘A’,
second row starts with ‘B’, etc.
• This cipher requires a keyword that the sender and
receiver know ahead of time
• Each character of the message is combined with
the characters of the keyword to find the
ciphertext character

61. 61
Vigenère Cipher Table
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
B B A B C D E F G H I J K L M N O P Q R S T U V W X Y
C C D E F G H I J K L M N O P Q R S T U V W X Y Z A B
D D E F G H I J K L M N O P Q R S T U V W X Y Z A B C
E E F G H I J K L M N O P Q R S T U V W X Y Z A B C D
F F G H I J K L M N O P Q R S T U V W X Y Z A B C D E
G G H I J K L M N O P Q R S T U V W X Y Z A B C D E F
H H I J K L M N O P Q R S T U V W X Y Z A B C D E F G
I I J K L M N O P Q R S T U V W X Y Z A B C D E F G H
J J K L M N O P Q R S T U V W X Y Z A B C D E F G H I
K K L M N O P Q R S T U V W X Y Z A B C D E F G H I J
L L M N O P Q R S T U V W X Y Z A B C D E F G H I J K
M M N O P Q R S T U V W X Y Z A B C D E F G H I J K L

62. 62
Vigenère Cipher Table (cont’d)
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
N N O P Q R S T U V W X Y Z A B C D E F G H I J K L M
O O P Q R S T U V W X Y Z A B C D E F G H I J K L M N
P P Q R S T U V W X Y Z A B C D E F G H I J K L M N O
Q Q R S T U V W X Y Z A B C D E F G H I J K L M N O P
R R S T U V W X Y Z A B C D E F G H I J K L M N O P Q
S S T U V W X Y Z A B C D E F G H I J K L M N O P Q R
T T U V W X Y Z A B C D E F G H I J K L M N O P Q R S
U U V W X Y Z A B C D E F G H I J K L M N O P Q R S T
V V W X Y Z A B C D E F G H I J K L M N O P Q R S T U
W W X Y Z A B C D E F G H I J K L M N O P Q R S T U V
X X Y Z A B C D E F G H I J K L M N O P Q R S T U V W
Y Y Z A B C D E F G H I J K L M N O P Q R S T U V W X
Z Z A B C D E F G H I J K L M N O P Q R S T U V W X Y

63. 63
Vigenere Cipher
• E.g., Message = SEE ME IN MALL
• Take keyword as INFOSEC
• Vigenère cipher works as follows:
S E E M E I N M A L L
I N F O S E C I N F O
-------------------------------------
A R J A W M P U N Q Z

64. 64
Vigenere Cipher
• To decrypt, the receiver places the keyword
characters below each ciphertext character
• Using the table, choose the row
corresponding to the keyword character and
look for the ciphertext character in that row
• Plaintext character is then at the top of that
column

65. 65
Vigenere Cipher
• Decryption of ciphertext:
A R J A W M P U N Q Z-column2
I N F O S E C I N F O-row1
-------------------------------------
S E E M E I N M A L L
• Best feature is that same plaintext character
is substituted by different ciphertext
characters (i.e., polyalphabetic)

66. 66
Multiple Letter Cipher
• Playfair cipher is a multiple letter cipher
• Each plaintext letter is replaced by a digram in this
cipher
• Number of digrams is 26 x 26 = 676
• User chooses a keyword and puts it in the cells of
a 5 x 5 matrix. I and J stay in one cell. Duplicate
letters appear only once.
• Alphabets that are not in the keyword are arranged
in the remaining cells from left to right in
successive rows in ascending order

67. 67
Playfair Cipher
• Keyword “Infosec”
I / J N F O S
E C A B D
G H K L M
P Q R T U
V W X Y Z

68. 68
Playfair Cipher
• Rules:
– Group plaintext letters two at a time
– Separate repeating letters with an x
– Take a pair of letters from plaintext
– Plaintext letters in the same row are replaced by letters
to the right (cyclic manner)
– Plaintext letters in the same column are replaced by
letters below (cyclic manner)
– Plaintext letters in different row and column are
replaced by the letter in the row corresponding to the
column of the other letter and vice versa

69. 69
Playfair Cipher
• E.g., Plaintext: “CRYPTO IS TOO EASY”
• Keyword is “INFOSEC”
• Grouped text: CR YP TO IS TO XO EA SY
• Ciphertext: AQ VT YB NI YB YF CB
OZ
• To decrypt, the receiver reconstructs the 5
x 5 matrix using the keyword and then uses
the same rules as for encryption

70. Transposition Ciphers
• consider classical transposition or
permutation ciphers
• these hide the message by rearranging the
letter order
• without altering the actual letters used
• can recognise these since have the same
frequency distribution as the original text
• Rail Fence and Vernam Ciphers
• Columnar Transposition Techniques

71. Rail Fence cipher
• write message letters out diagonally over a
number of rows
• then read off cipher row by row
• eg. write message out as:
m e m a t r h p r y
e t e f e t e a t
• giving ciphertext
MEMATRHTGPRYETEFETEOAAT

72. Vernam Cipher
• The only unbreakable stream cipher
– K: a long, non-repeating sequence of random numbers
Exclusive OR Exclusive ORPlaintext Ciphertext Plaintext
P PC
K K
Secret channel
1 0 =1; 0 1=1
0 0 =0; 1 1=0

73. Vernam Cipher
• An example of Vernam Cipher
– Alice:
– Bob:
1 0 =1; 0 1=1
0 0 =0; 1 1=0
P: 100 010 111 011 110 001…
K: 010 011 101 101 010 111…
C: 110 001 010 110 100 110…
P: 100 010 111 011 110 001…
K: 010 011 101 101 010 111…
C: 110 001 010 110 100 110…

74. Product Ciphers
• ciphers using substitutions or transpositions are
not secure because of language characteristics
• hence consider using several ciphers in succession
to make harder, but:
– two substitutions make a more complex substitution
– two transpositions make more complex transposition
– but a substitution followed by a transposition makes a
new much harder cipher
• this is bridge from classical to modern ciphers

75. Stegnographic Techniques
Greek Words:
STEGANOS – “Covered”
GRAPHIE – “Writing”
• Steganography is the art and science of writing
hidden messages in such a way that no one apart
from the intended recipient knows of the existence
of the message.
• This can be achieved by concealing the existence
of information within seemingly harmless
carriers or cover
• Carrier: text, image, video, audio, etc

76. Evolution of Steganography
440 BC
• Histiaeus, who shaved the head of his most trusted slave
and tattooed a message on it. After his hair had grown the
message was hidden. The purpose was to instigate a revolt
against the Persians.
• Demeratus sent a warning about a forthcoming attack to
Greece by writing it on a wooden panel and covering it in
wax.
World War II
• Invincible inks
• Null ciphers (unencrypted messages):
• Microdot Technology
-Shrinking messages down to the size of a dot became a
popular method. Since the microdot could be placed at the
end of a sentence or above a j or an i.
Disadv: Time, complex, not secure etc

77. Steganographic System
cover: cover is the original picture, audio or video
emb : embedded secret message
fE: steganographic function "embedding"
fE-1: steganographic function "extracting"
key: parameter which controls the hiding process of
the secret message
stego: resultant file that contains hidden message

78. Modern Steganography Techniques
Masking and Filtering: Is where information is hidden inside of a
image using digital watermarks that include information such as copyright,
ownership, or licenses. The purpose is different from traditional
steganography since it is adding an attribute to the cover image thus
extending the amount of information presented.
Algorithms and Transformations: This technique hides data
in mathematical functions that are often used in compression algorithms.
The idea of this method is to hide the secret message in the data bits in the
least significant coefficients.
Least Significant Bit Insertion: The most common and
popular method of modern day steganography is to make use of the LSB
of a picture’s pixel information. Thus the overall image distortion is kept
to a minimum while the message is spaced out over the pixels in the
images. This technique works best when the image file is larger then the
message file and if the image is grayscale.

79. Steganography Techniques
• Substitution methods(Steganography in Images)
Bit plane methods
Palette-based methods
• Signal Processing methods(Steganography in Images)
Transform methods
• Steganography in Audio
• Steganography in Text

80. Stegano-system Criteria
• Cover data should not be significantly modified ie
perceptible to human perception system
• The embedded data should be directly encoded in
the cover & not in wrapper or header
• Embedded data should be immune to
modifications to cover

81. Places to Hide Information:
Steganography
• Images
• Audio files
• Text
• Video
We focus on Images as cover media.
Though most ideas apply to video and audio
as well.

82. Steganography in Images
Way images are stored:
• Array of numbers representing RGB values for each pixel
• Common images are in 8-bit/pixel and 24-bit/pixel format.
• 24-bit images have lot of space for storage but are huge
and invite compression
• Proper selection of cover image is important.
• Best candidates: gray scale images ..
• Cashing on limitations of perception in human vision

83. Steganography: Bit plane Methods
• Image: replace least significant bit (LSB) of image
intensity with message bit
• Replace lowest 3 or 4 LSB with message bits or
image data (assume 8 bit values)
• Data is hidden in “noise” of image
• Can hide surprisingly large amounts of data this
way
• Very fragile to any image manipulation

84. Least Significant Bit
• Consider a 24 bit picture
• Data to be inserted: character ‘A’: (10000011)
• Host pixels: 3 pixel will be used to store one character of 8-bits
• The pixels which would be selected for holding the data are chosen on the
basis of the key which can be a random number.
• Ex: 00100111 11101001 11001000
00100111 11001000 11101001
11001000 00100111 11101001
Embedding ‘A’
00100111 11101000 11001000
00100110 11001000 11101000
11001001 00100111 11101001
• According to researchers on an average only 50% of the pixels actually
change from 0-1 or 1-0.

85. +
=
http://www.cl.cam.ac.uk/~fapp2/steganography/image_downgrading/
8-bit (256 grayscale)
images.
TOP SECRET

86. Sacrificing 2 bits of cover to carry 2 bits of
secret image
Original Image Extracted Image

87. Sacrificing 5 bits of cover to carry 5 bits of
secret image
Original Image Extracted Image

88. Palette-based Methods
• Palette manipulation means changing the way the
color or grayscale palette represents the image
colors
• Bit methods are used in palette manipulation
schemes
• Data hidden in “noise” of image
• Often radical color shifts occur - can tip off that
data is hidden
• Use grayscale to overcome color shift problem

89. Sample palettes
Red color
shade
variations
Drastic &
Subtle shade
variations
Gray Scale
shade
variations

90. Message: 0 1 1 0 0 1 0 1 0 1 1 1 0 1 0 1 0 1 0 0 0 1 1 1 1
Randomly chosen pixel with color
Find the color in the sorted palette
Sorted palette
Replace the LSB of the index to
color C1 with the message bit
The new index now points to a
neighboring color C2
Replace the index of the pixel in
the original image to point to the
new color C2.
index = 30 = 00011110
00011110
00011111
C1
C1
C2

91. Signal Processing Methods-
Transform Methods
• Discrete Cosine Transform
• Discrete Wavelet Transform
• Discrete Fourier Transform
• Mellin-Fourier Transform

92. Discrete Cosine Transform
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93. Discrete Fourier Transform
The formulae for the DFT and its inverse are
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2
2
exp
2
exp),(
1
),(
N
u
N
v N
vyj
N
uxj
vuF
N
yxa


94. Steganography in Audio
• Low Bit Coding
– Most digital audio is created by sampling the signal and
quantizing the sample with a 16-bit quantizer.
– The rightmost bit, or low order bit, of each sample can
be changed from 0 to 1 or 1 to 0
– This modification from one sample value to another is
not perceptible by most people and the audio signal still
sounds the same

95. Steganography in Audio
• Phase Coding
– Relies on the relative insensitivity of the human
auditory system to phase changes
– Substitutes the initial phase of an audio signal with a
reference phase that represents the data
– More complex than low bit encoding, but it is much
more robust and less likely to distort the signal that is
carrying the hidden data.

96. Steganography in Audio
• Direct Sequence Spread Spectrum
– Spreads the signal by multiplying it by a chip,
which is a maximal length pseudorandom
sequence
– DSSS introduces additive random noise to the
sound file

97. Steganography in Audio
• Echo Data Hiding
– Discrete copies of the original signal are mixed
in with the original signal creating echoes of
each sound.
– By using two different time values between an
echo and the original sound, a binary 1 or
binary 0 can be encoded.

98. Steganography in Text
• Soft Copy Text
– Encode data by varying the number of spaces
after punctuation
– Slight modifications of formatted text will be
immediately apparent to anyone reading the
text

99. Steganography in Text
• Soft Copy Text
– Use of White Space (tabs & spaces) is much
more effective and less noticeable
– This is most common method for hiding data in
text

100. Steganography in Text
• Soft Copy Text
– Encode data in additional spaces placed at the
end of a line
F o u r s c o r e a n d
s e v e n y e a r s a g o
o u r f o r e f a t h e r s

101. Steganography in Text
• Hard Copy Text
– Line Shift Coding
• Shifts every other line up or down slightly in order
to encode data
– Word Shift Coding
• Shifts some words slightly left or right in order to
encode data

102. Steganography in Text-Null
Cipher
• Message sent by a German spy during World war-I:
PRESIDENT’S EMBARGO RULING SHOULD HAVE
IMMEDIATE NOTICE. GRAVE SITUATION
AFFECTING INTERNATIONAL LAW. STATEMENT
FORESHADOWS RUIN OF MANY NEUTRALS.
YELLOW JOURNALS UNIFYING NATIONAL
EXCITEMENT IMMENSELY.
Pershing sails from NY June I.

103. Reference
• Asoke K Talukder, Manish Chaitanya, Architecting Secure Software
System, Aeurbach Publication, 2008
• Howard M, Lipner S, The Security Development Lifecycle, Microsoft
Press, 2006
• Frank Swiderski, Window Snyder, Threat Modeling, Microsoft Press,
2004
• John Viega, Gary McGraw, Building secure Software, How to Avoid
Security problems in the Right Way, Addison-Wesley 2001
• Tom Gallagher, Bryan Jeffries, Lawrence Landauer, Hunting Security
Bugs, Microsoft Press, 2006
• Ross Anderson, Security Engineering: A guide to Building dependable
Distributed systems, John wiley, 2001.