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C . M

,

.

C :

E C . ATM, C C

P A . G, F

T M M

E

. D

. T

.

T .... (

) (),

.

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T CIPHERS, STEGNOGRAPHY,

VISUAL CRYPTOGRAPHY

CLASSICAL CRYPTOGRAPHY

MONOALPHABETIC CIPHERS:

T

.

T :

) :

T .

.

A C J C

!!!!!

I

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E() =(+) 26

D() =() 26 (, Z26)

I =D (E())

F 3: A B C D.......

C D E F G........

S 25 26

27 1 .

) :

T ; ,

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

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

S >>

T 26! D !!

E C ( ),

>>, >> , >> ....

)

M

0

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plaintext: A F F I N E C I P H E R

x: 0 5 5 8 13 4 2 8 15 7 4 17

5x+ 8 8 33 33 48 73 28 18 48 83 43 28 93

T GCD (,26) =1,

12 1, 3 , 5, 7 , 9 ,11, 15, 17, 19, 21,23, 25 26 .

T 12*26 = 312.

POLYALBHABETIC CIPHERS:

T .

.

)

T . I ,

.. .

I :

=

P=

C = ( 0, 1, 2 )

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A : =

P=

C = ( 0, 3, 0, 3)

T ,

,

.

)

H .

E . O

: A = 0, B =1...Z=25, cipher.

A ,

, 26.

F

C 'ACT', ( GYBNQKURP ):

S 'A' 0, 'C' 2 'T' 19, :

T :

W POH.I , ,

(IFKVIVVMI )

)

T

. A . (T

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).T

. B

,

.T

.

E:

L = 3.

K = 2 1 3

P: CRYPTOGRAPHY

B : CRY PTO GRA PHY

C : RCY TPO RGA HPY .. RCYTPORGAHPY.

BLOCK CIPHER

T (

) .

( ) .

T .

T :

) ()

I . T

,

, .

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I , ECB

. T,

. T ECB

. I ECB, .

) ()

CBC .

P , XOR

. A ,

XOR . T

XOR (IV),

. CBC

ECB

. S ,

. T

CBC

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. A

.

[XOR . I

XOR . T

1, , 0 .

FEISTEL CIPHERI . T

, (L) (R),

. A ,

() ,

XOR . T . T

XOR

. T .

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E

:

D E S

(DES): I

(SPN) . I

56 . T

.

A E

S (AES):E AES

128

, 128,192 256 ,

MODERN CRYPTOGRAPHY: PUBLIC

KEY CRYPTOGRAPHYT

,

. E

. T

, . M

'

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. T ,

(.., )

. I

1970.P

,

I T L S (TLS) (

SSL), PGP GPG

I

,

,

. S

.

CRYPTOGRAPHIC ATTACKS

A

,

, . T

" .

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TYPES OF CRYPTOGRAPHIC ATTACK

A

.

A

. W

, C C,

.

A

. T

, .

A

. T

(

). T ;

.

A . I

.

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STEGANOGRAPHY

S . W

,

. G

.

T ,

.

LEAST SIGNIFICANT BIT (LSB)INSERTION:

T

. I ,

LSB

. I 24 ,

. A

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, ( )

RGB :

10010101 00001101 11001001

10010110 00001111 11001010

10011111 00010000 11001011

N "" 9 (

): 101101101. I

9 LSB 9 ,

( ):10010101 00001100 11001001

1001011 00001110 1100101

10011111 00010000 11001011

N 9

4, 50%, LSB.

T . S

8 , , . G , ,

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