I'm a bit confused about AES.
If a byte like an "a" or "4" occurs in the same location in the state, would not it be encrypted in the same form?
For example, if an "a" occurs in the top left hand corner of the 4 X 4 byte state, it seems to me that it would be enciphered the same everytime it happened to repeat in the same location.
Therefore, if you have plenty of known headers or other plaintext you might be able to compile an inventory of at least all alphanumeric characters in each location of the state.
Then it would be simply a matter of counting the bytes.
I am not saying it would reveal the key, but could you crack the rest of the message this way.
Am I missing something here?