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

From: Michael Amling (nospam@nospam.com)
Date: 02/24/03 

Date: Sun, 23 Feb 2003 20:43:03 -0600
From: Michael Amling <nospam@nospam.com>

Pathos wrote:
>
> 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] (?!?!).

   The key schedule starts out with the key, unmodified. Only after that
verbatim copy of the key are entries in the key schedule calculated from
previous entries.

--Mike Amling

Relevant Pages

  • :::Low level question about AES implementation:::
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  • Re: :::Low level question about AES implementation:::
    ... > It's in the key expansion. ... > key, the second word, word, in the key schedule would be the XOR between ... > the preceding word, wordthat is the original cipher key, and the word 8 ...
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