Okay, so, first I want you to copy the entire plaintext from the previous post. Then I want you to click this link. Paste the ciphertext into the big empty box under the words "Enter your ciphertext or comparison text here:" and click Submit. You should see a page with 3 tables. Look at the one whose cells are mostly green and whose title is "Most common digraphs". It will then list the frequency of the digraphs in the ciphertext and tell you which one appears the most. I have never actually told you which digraphs appear the most often in the English language, but we can figure out which ones do based on the monograph frequencies. The most common word in the English language is "THE" so we would expect the digraphs "TH" and "HE" to be very high up on the list. We could also say that "TH" would probably appear more often than "HE" because it also appears in many other words. You may notice that the table also gives us the frequency of the reversed digraph. This is extremely useful when trying to decrypt a ciphertext encrypted with playfair because if you examine the algorithm playfair uses for encryption you will realize that if "QP" gets encrypted as "KL", "PQ" must get encrypted as "LK". In the table, the darker the shade of green, the more appearances of the digraph. In the English language, there is one very common digraph whose reverse digraph is almost just as equally as common. This pair of letters is "ER" (or "RE"). If we look at the table the pair of digraph and reverse digraphs that are both very high in frequency are the pairs "CD" and "DC". Also, the highest frequency is the digraph "QL" and the second highest is "LM". We can now safely assume that "QL" is "TH", "LM" is "HE" and "CD" is "RE" and "DC" is "ER". Our goal is to find the correct key array, then we can decrypt the entire ciphertext. We can probably say that the last row of our 5 by 5 key table is "V W X Y Z" since these letters will probably not appear in our keyword. Now, we need to identify more digraphs before beginning to construct our key table. It is very likely that somewhere in the passage the phrase "THAT THE" will appear. If it does and is spaced like this: "TH AT TH E*" (* represents an unknown character) then we we know that in the ciphertext will be "QL ** QL **". We can look in our ciphertext for two QL's separated by 2 characters, and then assume that those two characters are AT. It turns out that "QL ** QL" appears 3 times in our ciphertext and in every single one of the times the ** was "CQ". We now can say that "QL" is "TH", "LM" is "HE" and "CD" is "RE" and "CQ" is "AT". We are now done with the first step, we have figured out what a sufficient number of digraphs are. Step 2, which will be the next post, is figuring out what the key array is based on this.