CODEWITHSUNDEEP
matrixcryptography
mickm
mickm

Reputation: 391

Hill Cipher using a 2 x 2 Key Matrix

I'm new to cryptography and I cannot seem to get my head around this problem: The problem says that the Hill Cipher using the below 2 x 2 key matrix (K) was used to produce the ciphered text "KCFL". 

K = (3   5)
    (2   3)

It then asks to use the Hill Cipher to show the calculations and the plain text when I decipher the same encrypted message "KCFL".

I know with other matrices, e.g. for the determinant there is usually a formula, such as:

a x d - b x c

However, for the Hill Cipher I am completely lost.

I have done the following:

a) found the inverse of K:

 K inverse =    (-3  5)
                (2  -3)

b) Found "KFCL":

KFCL = (10  5)
       (2  11)

c) The next step (mod 26) confuses me. How do I decipher (using mod 26) and the Cipher Key to find the plain text?

Any help is greatly appreciated.

Many thanks.

Upvotes: 1

Views: 14906

Answers (1)

anonymous
anonymous

Reputation: 1317

To perform MOD26 of the matrix, take each number and MOD26. If the number is negative, add multiples of 26 until you hit a positive number.

This may also help you.

26 modulo in hill cipher encryption

Upvotes: 1

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