Is the position of
the characters of the plaintext
1. Rail Fence Technique
In this case will be given
plaintext and dept =2 or depth=3
Step 1 : Arrange the alphabets of
the plain text diagonally
Step 2 : The cipher text will be
read as row –wise
Ex : Dept = 2 , Given text à Come home
C M
H M
O E
O E
From this case, the cipher text
will be C M H M O E O E
Depth= 3
C H
O E O E
M M
From this case, the cipher text
will be CH OEOE MM
2. Simple Columnar
In this step will be given Plaintext (PT) and Random number
of columns
Step 1 : Arrange the alphabets of the plaintext row-wise in
the number of columns decided by the user
Step 2 : Specify the random order of columns.
Step 3 : Write the cipher text alphabets according to the
order in step 2
Ex:
Given à
Number of columns 1-6 , Plain Text à
Come Home Tomorrow
1
|
2
|
3
|
4
|
5
|
6
|
C
|
O
|
M
|
E
|
H
|
O
|
M
|
E
|
T
|
O
|
M
|
O
|
R
|
R
|
O
|
w
|
So the Chiper text wil be 6,4,3,1, 2,5 oo,eow,mto,cmr,oer,hm or
6,5,4,3,2,1 its random.
In this case the Cipher text can be applied for second time
so the plain text can’t be easily read.
1
|
2
|
3
|
4
|
5
|
6
|
O
|
O
|
E
|
O
|
W
|
M
|
T
|
O
|
C
|
M
|
R
|
O
|
E
|
R
|
M
|
H
|
3. One-time Pad or VERNAM CIPHER
In this case
will be given PT and One-time Pad and A=0
Step 1 :
Convert the alphabets of the plaintext into their corresponding numerical
equivalents.
Step 2 : Convert
the alphabets of the one-time pad into their corresponding numerical
equivalents.
Step 3 : Add
the corresponding numerical equivalents with the numerical equivalents of
one-time pad.
Step 4 :
Subtract 26 if the sum is greater than
25
Ex:
PT à
H O W ARE YOU
One-time Pad
à N C B T Z Q A R X
Change it into
numerical code & add them each
PT
|
H
|
O
|
W
|
A
|
R
|
E
|
Y
|
O
|
U
|
7
|
14
|
22
|
0
|
17
|
4
|
24
|
14
|
20
|
|
OTP
|
N
|
C
|
B
|
T
|
Z
|
Q
|
A
|
R
|
X
|
Step 3
|
13
|
2
|
1
|
19
|
25
|
16
|
0
|
17
|
23
|
SUM
|
20
|
16
|
23
|
19
|
42
|
20
|
24
|
31
|
43
|
Step 4
|
26
|
26
|
26
|
||||||
20
|
16
|
23
|
19
|
16
|
20
|
24
|
5
|
17
|
|
Ciphtxt
|
U
|
Q
|
X
|
T
|
Q
|
U
|
Y
|
F
|
R
|
Decryption :
In this case
will be given One-time pad
Step 1 :
Convert the alphabets of the plaintext into their corresponding numerical
equivalents.
Step 2 : Convert
the alphabets of the one-time pad into their corresponding numerical
equivalents.
Step 3 :
Subtract one-time pad from cipher text
Step 4 : If
the different is negative than add 26 to it.
CT
|
U
|
Q
|
X
|
T
|
Q
|
U
|
Y
|
F
|
R
|
20
|
16
|
23
|
19
|
16
|
20
|
24
|
5
|
17
|
|
OTP
|
N
|
C
|
B
|
T
|
Z
|
Q
|
A
|
R
|
X
|
Step 3
|
13
|
2
|
1
|
19
|
25
|
16
|
0
|
17
|
23
|
SUM
|
7
|
14
|
22
|
0
|
-9
|
4
|
24
|
-12
|
-6
|
step 4
|
26
|
26
|
26
|
||||||
7
|
14
|
22
|
0
|
17
|
4
|
24
|
14
|
20
|
|
PlainText
|
H
|
O
|
W
|
A
|
R
|
E
|
Y
|
O
|
U
|
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