I was thinking about what happens if we ommit one operation of AES. If we ommit ADDROUNDKEY then AES is trivial. But what happens if we ommit SUBBYTES? I was thinking about the linearity of the encryption. If we ommit SubBytes then all non linearity of aes is gone right? And what happens if we ommit MIXCOLUMNS? I can see that we can attack each block separately but I can't explain anything else. Some help?