Mixed Alphabet Keyword

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Presentation transcript:

Mixed Alphabet Keyword In this method we must have a keyword with plaintext, the steps of this method are explained below:- 1. Write the alphabet letters from a to z. 2. Take the keyword with no repeated letters (no repeated letters must be found). 3. Put the new keyword under the corresponding alphabet and the alphabet letters that is not found in the keyword must be added to the end of the keyword.

Mixed Alphabet Keyword(encryption) Plaintext = “ALMAMONUNIVERSITY” KEY =”MATHMATIC” Remove duplicate Cipher text =BRUBUWVTVOHJZMO KEY =MATHIC” A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Mixed Alphabet decryption))Keyword Cipher text =BRUBUWVTVOHJZMO KEY =”MATHMATIC” KEY =MATHIC” B D F G J K L N O P Q R S U V W X Y Z M A T H E I C Plaintext = “ALMAMONUNIVERSITY”

Mixed Alphabet Keyword keyword = REGINA A B C D E F G H I J K L M N O P Q R S T U V W X Y Z plaintext = ALMAMONCOLLEGE cipher text= RDMRMIUKIDDYCY

Multiplicative

Multiplicative Using the following forms for ciphering and deciphering respectively:- C= (P*K) mod 26 where GCD (K, 26) =1 and GCD is the Greatest Common Devisor P=(C*K-1) mod 26

Multiplicative Ex: Encryption K=9 Plain text = ALM EK(m) =(m*k) mod 26 E9(A) =(0*9) mod 26 = 0 = A E9(L) =(11*9) mod 26 =99 mod 26 = 21 = V E9(M) =(12*9) mod 26 =108 MOD 26 = 4 = E Cipher text = “AVE

Ex: Encryption K-1 = 3 Cipher text = AVE DK(p) =(p Ex: Encryption K-1 = 3 Cipher text = AVE DK(p) =(p*k-1) mod 26 D3(A) =(0*3) mod 26 = 0 = A D3(V) =(21*3) mod 26 =63 mod 26 = 11 = L D3(E) =(4*3) mod 26 =12 MOD 26 = 12 = M

Shift + Multiplicative (Affine Cipher

Shift + Multiplicative (Affine Cipher For ciphering:- C= (P*K1 + k2) mod 26 with K1 is a prime number T= (P*K1) mod 26 C= (T+K2) mod 26 For deciphering:- P=((C-K2)*K1-1) mod 26 T= (C-K2) mod 26 P=(T*K1-1) mod 26

Shift + Multiplicative (Affine Cipher Example:Use an affine cipher to encrypt the message “hello” with the key pair (7, 2).

Shift + Multiplicative (Affine Cipher) Encryption Plaintext= omar and K1 =3 and K2 =2 C(o) = (14*3+2) mod 26 = 44 mod 26 = 18 → S C(m) = (12*3+2) mod 26 = 38 mod 26 = 12 → m C(a) = (0*3+2) mod 26 = 2 → c C(r) = (17*3+2) mod 26 = 53 mod 26 = 1→ b ∴ C= smcb

Shift + Multiplicative (Affine Cipher) Now for deciphering "zebbw" with key pair (7, 2):- k-1 (7)=15 P(z) = ((25-2)* 15) mod 26 =(23*25) mod 26 = 345 mod 26 =7 → h P(e) = ((4-2)* 15) mod 26 =2*15 mod 26 =30 mod 26 = 4 → E P(b) = ((1-2)* 15) mod 26 =-1*15 =-15mod 26 =(26-15)=11 → L P(b) = L P(w) = ((22-2)*15) mod 26 =14 → o ∴ P= hello