Vigenere cipher Method 1 and 2

1. Presented By:
Abd-ur Rehman Saqib
Sajid Iqbal
Presented To:
Sir Adil Waheed
Topic:
Vigenere Cipher
BS.IT(2016-2020)UE Jauharabad

2. Vigenere Cipher:
 Designed by Blasic de Vigenere(16th centaury French
Mathematization)
 Vigenere Cipher is a method of encrypting alphabetic
text.
 It uses a simple form of polyalphabetic substitution.
 A polyalphabetic cipher is any cipher based on
substitution, using multiple substitution alphabets .
 The encryption of the original text is done using the 26
by 26 Matric or Vigenère table.

3. Method 1: Vigenere Table:
 Plain Text: Give Money
 Key: Lock
 Repeat the Letter of the Key so
That the No of Letters is P and
K is Plaintext and Key
becomes Equal.

4. P.T = G
Key= L
C.T = R

5. P.T = i
Key= O
C.T = W

7.  After the Process the Cipher Text is Following:
C.T= R W X O X C P O J

8. For Decryption:

9. Method 2: When Table is Not Given:
Encryption
The plaintext(P) and key(K) are added
modulo 26.
Ei = (Pi + Ki) mod 26
Decryption
Di = (Ei - Ki + 26) mod 26

10. For Example:
 Plain Text: She Is Listening
 Key: Pascal
 Setup 1: Make a table

11. Setup 2:

12. Setup 3: Apply the Formula:
 For Encryption
Ei = (Pi + Ki) mod 26
Where P is Plain Text Value and k is key stream value
For example:
P=18,K=15 so
Ei = (18 + 15) mod 26
Ei = 33 mod 26
Ei = 7

13. After Formula:

14. Output:

15. Decryption
 Formula
Di = (Ei - Ki + 26) mod 26
Where E is cipher text and k is Key values
For example
E=7,K=15 so
Di = (Ei - Ki + 26) mod 26
Ei = (7-15+26) mod 26
Ei = 18 mod 26
Ei = 18

16. After Formula:

17. Output: