I've been trying to solve this question from Forouzan's book ("Cryptography And Network Security") and haven't been able to wrap my head around how to solve it.
The plaintext “letusmeetnow” and the corresponding ciphertext “HBCDFNOPIKLB” are given. You know that the algorithm is a Hill cipher, but you don’t know the size of the key.
Find the key matrix.
I inverse the 2x2 plaintext matrix and multiple with a 2x2 ciphertext matrix and take a mod 26. However, the key matrix is always in fractions, never an integer.
It would be great if someone could point me in the right direction / tell me what I'm doing wrong.
Thanks in advance!