As part of an assignment, I have been given a cipher text of
with the following description,
A zebra could unlock this German, 1st World War cipher.
At first, I thought that the description could contain a Playfair keyword that could be used to crack the ciphertext. However, the ciphertext is 25 characters long - shouldn't the plaintext be padded before encryption to create an even number of characters? Also, I don't see how Playfair encryption could yield repeating characters in a pair like "FF" or "XX".
I was hoping someone could validate my reasoning behind this and maybe point me in the right direction (in terms of determining which encryption method has been used).