:::Low level question about AES implementation:::

From: Pathos (pathos@mail.pt)
Date: 02/23/03 

From: "Pathos" <pathos@mail.pt>
Date: Sun, 23 Feb 2003 22:18:09 -0000

Hi there...

It's in the key expansion.

The fisrt word of the Key Schedule, word[0], is the cipher key, the next
words, are a XOR between the preceding word and the word Nk positions
before, if i'm correct. (there are some other stuff to consider, like when
the word index is a multiple of Nk, but let's keep it simple for now)

Now, here's what i can't understand, if Nk=8, so this would be a 256 bits
key, the second word, word[1], in the key schedule would be the XOR between
the preceding word, word[0] that is the original cipher key, and the word 8
positions before, 8 positions before would be word[-6] (?!?!).

I'm understanding this wrongly for sure, can someone explain this small
detail to me.

Thanks for your time
Pedro Azevedo

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