(Simple regular transposition cipher) You know that the following ciphertext was encrypted using a regular columnar transposition with key-length 5.

HLHLN IPTED OEASP SRCWT EEAEM YSIEO EAGNR HDOTL NEHOI KHETD NSETP TTIPS IORSE DNRRO

a) How many rows does each column consist of?

b) Identify the columns in the ciphertext and pick the first three letters in each column.

c) Anagram the first three letters of each column so obtain the beginning of the plaintext.

d) Based on the order of the columns you found in

c) find the whole plaintext.