From this slide you will learn about Cryptology's Caesar Cipher method where you will learn how to encrypt or decry-pt a message.

1. Cryptology
CAESAR CIPHER

2. How to encrypt a message?
 By using a formula .
 What is the formula?
 F(p) = (p+3) mod 26 (Encryption formula)
 F−1
(p) = (p-3) mod 26 (Decryption formula)
 The values of p is 0 to 25
 These are the numeric values of the characters (A-Z)
 Like A = 0 , B = 1, C = 2 , D = 3, E = 4 etc.

3. Write down the following chart before every
problem of cryptology in exam hall.
Characters Values
A 0
B 1
C 2
D 3
E 4
F 5
G 6
H 7
I 8
J 9
Characters Values
K 10
L 11
M 12
N 13
O 14
P 15
Q 16
R 17
S 18
T 19
Characters Values
U 20
V 21
W 22
X 23
Y 24
Z 25

4. Steps of Encryption/Decryption
1. First find out the letters(given) numeric values.
2. Then use the appropriate formula.(Encryption/ Decryption)
3. After using the appropriate formula you will get values from 0-25
for each character.
4. Then find the values from the chart.
5. Use new character according to the assigned values in the chart
for every character.
6. Its done.

5. Lets Encrypt a message.
The unique letters we found from the following message are T, E, S, O, D, A, Y
F(p) = (p+3) mod 26 (Encryption formula)
F(19) = (19+3) mod 26 = 22 mod 26 = 22 = W
F(4) = (4+3) mod 26 = 7 mod 26 = 7 = H
F(18) = (18+3) mod 26 = 21 mod 26 = 21 = V

6. Others
F(14) = (14+3) mod 26 = 17 mod 26 = 17 = R
F(3) = (3+3) mod 26 = 6 mod 26 = 6 = G
F(0) = (0+3) mod 26 = 3 mod 26 = 3 = D
F(24) = (24+3) mod 26 = 27 mod 26 = 1 = B

7. Now replace the characters with new
characters.
TEST TODAY = WHVW WRGDB
So our encrypted message is WHVW WRGDB

8. Lets Decrypt a message.
The unique letters we found from the following message are O, R, Y, H
F−1
(p) = (p-3) mod 26 (Decryption formula)
𝐹−1
(14) = (14-3) mod 26 = 11 mod 26 = 11 = L
𝐹−1
(17) = (17-3) mod 26 = 14 mod 26 = 14 = O
𝐹−1
(24) = (24-3) mod 26 = 21 mod 26 = 21 = V
𝐹−1(7) = (7-3) mod 26 = 4 mod 26 = 4 = E

9. Now replace the characters with new
characters.
ORYH = LOVE
So our Decrypted message is LOVE

10. Exercises
1.ENCRYPT THE MESSAGE
“KOS KI MAMA ”
2.DECRYPT THE MESSAGE “L
ORYH EDQJODGHVK”