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Vernam Cipher Part a requires you to encrypt the plaintext Part b requires you t

ID: 3593071 • Letter: V

Question

Vernam Cipher

Part a requires you to encrypt the plaintext

Part b requires you to covert the encrypted cyphertext to plaintext

A=1, B=2, …, Z=26

a)

Plaintext:

I

N

F

O

R

M

A

T

I

O

N

I

S

I

M

P

O

R

T

A

N

T

Plain Text value

One-Time Pad Text

P

G

R

I

F

K

X

L

Q

A

J

M

C

H

B

D

E

O

S

V

P

N

One-Time Pad Value:

Sum of plaintext pad:

After modulo subtract:

Cypertext:

b)

Plaintext:

Plain Text value

One-Time Pad Text

X

F

J

W

D

A

E

T

O

U

C

G

B

L

I

H

One-Time Pad Value:

Sum of plaintext pad:

After modulo subtract:

Cypertext:

Y

X

O

V

S

V

X

U

U

Z

R

U

N

U

W

M

Plaintext:

I

N

F

O

R

M

A

T

I

O

N

I

S

I

M

P

O

R

T

A

N

T

Plain Text value

One-Time Pad Text

P

G

R

I

F

K

X

L

Q

A

J

M

C

H

B

D

E

O

S

V

P

N

One-Time Pad Value:

Sum of plaintext pad:

After modulo subtract:

Cypertext:

Explanation / Answer

Plaintex

t:

I

N

F

O

R

M

A

T

I

O

N

I

S

I

M

P

O

R

T

A

N

T

Plain Text value

9

14

6

15

18

13

1

20

9

15

14

9

19

9

13

16

15

18

20

1

14

20

One-Time Pad Text

P

G

R

I

F

K

X

L

Q

A

J

M

C

H

B

D

E

O

S

V

P

N

One-Time Pad Value:

16

7

18

9

6

11

24

12

17

1

10

13

3

8

2

4

5

15

19

22

16

14

Sum of plaintext pad:

25

21

24

24

24

24

25

32

26

16

24

22

22

17

15

20

20

33

39

23

30

34

After modulo subtract:mod 26

25

21

24

24

24

24

25

6

0

16

24

22

22

17

15

20

20

7

13

23

4

8

Cypertext:

Y

U

X

X

X

X

Y

F

Z

P

X

V

V

Q

O

T

T

G

M

W

D

H

(a)

26 Mod 26 =0 0 no value so take Z=0 or 26

b)

Cypertext

Y

X

O

V

S

V

X

U

U

Z

R

U

N

U

W

M

Cypertext value

25

24

15

22

19

22

24

21

21

26

18

21

14

21

23

13

One-Time Pad Text

X

F

J

W

D

A

E

T

O

U

C

G

B

L

I

H

One-Time Pad Value:

24

6

10

23

4

1

5

20

15

21

3

7

2

12

9

8

subtration of cypertext- key:

1

18

5

-1

15

21

19

1

6

5

15

14

12

9

14

5

After modulo:26

1

18

5

25

15

21

19

1

6

5

15

14

12

9

14

5

plaintext:

A

R

E

Y

O

U

S

A

F

E

O

N

L

I

N

E

Plaintex

t:

I

N

F

O

R

M

A

T

I

O

N

I

S

I

M

P

O

R

T

A

N

T

Plain Text value

9

14

6

15

18

13

1

20

9

15

14

9

19

9

13

16

15

18

20

1

14

20

One-Time Pad Text

P

G

R

I

F

K

X

L

Q

A

J

M

C

H

B

D

E

O

S

V

P

N

One-Time Pad Value:

16

7

18

9

6

11

24

12

17

1

10

13

3

8

2

4

5

15

19

22

16

14

Sum of plaintext pad:

25

21

24

24

24

24

25

32

26

16

24

22

22

17

15

20

20

33

39

23

30

34

After modulo subtract:mod 26

25

21

24

24

24

24

25

6

0

16

24

22

22

17

15

20

20

7

13

23

4

8

Cypertext:

Y

U

X

X

X

X

Y

F

Z

P

X

V

V

Q

O

T

T

G

M

W

D

H