_Affine Ciphere Ciphere Ciphere Ciphere.pptx

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1. Section 3 GCD Affine Cipher

2. GCD  

3. GCD gcd(30,12) = gcd(12,30 mod 12) = gcd(12,6) =gcd(6,12 mod 6) = gcd(6, 0) = 6

4. Affine Cipher  

5. Encryption We have to add the alphabet letters abcefghijklmnopqurstuvwxyz 01234567…………… the number of letter h is 6 Key = (7,2) F(6) = 7 (6) + 2 = 44 it is greater than the domain 44 mod 26 = 18 with letter s

6. Encryption If the result is = 57 then subtract from it 26 It will give 33 So, then subtract another 26 it will be 7 and it will be letter “i”.

7. Decryption  

8. Decryption y = 15*(4-2) = 30 for letter “e” 30 mod 26 = 4 which is letter “e” y = 15*(1-2) = -15 for letter “b” -15 mod 26 = 11 which is letter “l” y = 15*(22-2) = 300 for letter “w” 300 mod 26 = 14 which is letter “o”