I am able to decrypt Vigenere ciphertext using the index of coincidence and chi-squared test.
However, out of interest, how do you go about attacking ciphertext that was encrypted using a mixed alphabet shifted 26 times?
Also, what about a ciphertext that has been encrypted with 26 random alphabets? (so each line in the tableau is random)
Googling seems to bring up the basic Vigenere, but either an example or a link to a more detailed resource would be good.