Given a keyword, you can encrypt a message using alphabetical substitution like this:
plain: 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 cipher: C I P H E R A B D F G J K L M N O Q S T U V W X Y Z result: C A K S Y I B L T Z P D M U H F N V E G O W R J Q X
My problem is my professor literally never covered this topic and is putting on our upcoming exam. The example problem he gave us is as follows...
Use your knowledge of Substitution Ciphers to find the keyword:
I have tried using frequency analysis of the ciphertext, I found that the most common plaintext letters for the keyword are "e","t", "i", "a", and possible "o" and "c".
Is there something I am missing?
EDIT: Looking online, I learned this is something called a Playfair cipher. Still cannot solve it though :( i don't know why I am having so much trouble with this.