Breaking Machine CiphersThis section will deal with cryptanalysis of slightly more advanced ciphers such as Enigma and M-209 used during the second world war. These are a fair bit more complicated than the simple examples provided elsewhere, however they still rely heavily on the techniques developed such as hill climbing, using the Index of Coincidence, and quadgram statistics.
The 'Pigeon Cipher' is a cipher found by a man cleaning his chimney in England. In the chimney, a dead pigeon was found with this message fixed to its leg. It dates from the second World War, and is so far unsolved.
This page will deal with ciphertext only cryptanalysis of the enigma cipher. It is based on the paper by Jim Gillogly.
In part 1, we looked at breaking enigma with no plugboard. In this part, we will look at a known ciphertext attack on Enigma with a plugboard, then we will generalise the attack to ciphertext only.