(Simple regular Transposition Cipher) You suspect the following text to have been the result of a regular transposition cipher.

CHEIU EKEAY IDAOS SEFYT NETNF BLEIH ECOOT YCFNN YIREM CTTNC ROEON W

a) Determine all possible key lengths (based on the fact that it is a regular cipher) in the range 3 - 12.

b) You found out (dont ask how) that the plaintext contains the word efficiency. Determine which letter sequences would have to occur in the ciphertext for every possible keylength you determined in a. E.g. for key-length 3 (which isnt possible), For each of the possible key-lengths you determined in a) determine which letter sequences would have to occur in the ciphertext, the ciperhtext would have to contain EIEY, FCN, and FIC, but it doesnt contain any of these.

c) Based on the key-length you determined in b) break the transposition cipher through anagramming. As in problem 3, you may want to determine the order of the column using just the top two or three rows.