Reply To: Mission 5A
Excellent work so far agent professor-count, as you correctly observed, the frequencies are very close to standard English, so there can’t be any serious substitution going on, and the cipher must be disguising the text some other way.
The most common method is to use some kind of anagramming, or transposition cipher, to jumble the plaintext letters, so your task is to unjumble them. Looking for cribs might help, but the first task is to try to decide what length blocks might have been jumbled, as transposition ciphers typically repeat the anagram repeat on a regular basis. Sometimes you will see padding characters added to the message to maintain the patter at the beginning or end, and that can give you a clue to the repeat period. (How many letters are in the padded message? What repeats go into that? What is reasonable?)
You can use a text processor (with a pattern replace like grep) or a spreadsheet like Excel to do the hard work of reassembling the message into plain text, or even to play around with the text to see what might work. You can place the text into rows of a given length, then shuffle them by copy and pasting columns in the sheet.
Hope this helps to get you (and others) over the line.
Good luck,
Harry