Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

a) Given plaintext \"LOVE\" , if we know the encryption algorithem is Affine Cip

ID: 3724766 • Letter: A

Question

a) Given plaintext "LOVE" , if we know the encryption algorithem is Affine Cipher and we know the key (a,b) = (7,9), please generate the ciphertext.

b) Based on the Affine Cipher in a) if you receive a ciphertext 'VDT" please decrypt it to the original.

c) Given plaintext "LOVE" , if we know the enceyption algorithem is Vignere ciphere and we know the key (7,9) please generate the cipheretext.

d) Based on vigenere ciphere in c) if you receive a ciphertext "ABCD" PLEASE DECRYPT IT TO THE ORIGINAL PLAINTEXT.

Explanation / Answer

1. We will use the below values for every letter

PLAIN TEXT = LOVE

The corresponding values will be 11 14 21 4

Multiplying the first number 7 of the key to every value. The new values will be 77 98 147 28

Adding second number 9 to the corresponding values : 86 107 156 37

Taking mod 26 : 8 3 0 11

putting the letters corresponding to numbers . Cipher text will be : IDAL

2. VDT will hava value as 21 3 19

subtracting the second value 9 from the key : 12 -9 10

26 mod (inverse of 7) : 24 14 20

Thus the plain text as putting the corresponding values will be : YOU.

3,4 . vignere cipher doesnot have a numeric key as it is based on the table below

            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

        A   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

        B   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 A

        C   C D E F G H I J K L M N O P Q R S T U V W X Y Z A B

        D   D E F G H I J K L M N O P Q R S T U V W X Y Z A B C

        E   E F G H I J K L M N O P Q R S T U V W X Y Z A B C D

        F   F G H I J K L M N O P Q R S T U V W X Y Z A B C D E

        G   G H I J K L M N O P Q R S T U V W X Y Z A B C D E F

        H   H I J K L M N O P Q R S T U V W X Y Z A B C D E F G

        I   I J K L M N O P Q R S T U V W X Y Z A B C D E F G H

        J   J K L M N O P Q R S T U V W X Y Z A B C D E F G H I

        K   K L M N O P Q R S T U V W X Y Z A B C D E F G H I J

        L   L M N O P Q R S T U V W X Y Z A B C D E F G H I J K

        M   M N O P Q R S T U V W X Y Z A B C D E F G H I J K L

        N   N O P Q R S T U V W X Y Z A B C D E F G H I J K L M

        O   O P Q R S T U V W X Y Z A B C D E F G H I J K L M N

        P   P Q R S T U V W X Y Z A B C D E F G H I J K L M N O

        Q   Q R S T U V W X Y Z A B C D E F G H I J K L M N O P

        R   R S T U V W X Y Z A B C D E F G H I J K L M N O P Q

        S   S T U V W X Y Z A B C D E F G H I J K L M N O P Q R

        T   T U V W X Y Z A B C D E F G H I J K L M N O P Q R S

        U   U V W X Y Z A B C D E F G H I J K L M N O P Q R S T

        V   V W X Y Z A B C D E F G H I J K L M N O P Q R S T U

        W   W X Y Z A B C D E F G H I J K L M N O P Q R S T U V

        X   X Y Z A B C D E F G H I J K L M N O P Q R S T U V W

        Y   Y Z A B C D E F G H I J K L M N O P Q R S T U V W X

        Z   Z 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