Below is an example of ciphertext obtained from an Affine Cipher. Determine the plaintext.
Probabilities of each letter:
The Attempt at a Solution
Well, due to occurrences and the probabilities, you try mapping two letters to other letters then solve using modular arithmetic. I have tried mapping C--> E then B--> every other letter, C--> T and B--> all letter with a higher probability then R, and C--> A and B--> all letters with a higher probability then R.
Just to make sure I am doing all calculations right, assume C-->E and B--> T
Then we have the equations 2a+b=4 (mod 26)
a+b=19 (mod 26)
This means a=11, b=8 and since GCD(11,26)=1 the deciphering equation will be
d(k) = 7(y-8) (mod 26)
But, using this equation the first five letters map to OEYLE which is obviously nothing, so I have to try the next one.
I have been working on this for over 5 hours and have not come up with a solution. Any help would be greatly appreciated!