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I'm implementing AES encryption. During the mix column/inverse mix columns procedures, I need to do Galois field multiplication. I'm using the look-up tables in the following document(Section 5.4.2) https://www.ime.usp.br/~rt/cranalysis/AESSimplified.pdf

If you go to the section specified above, the (0,0) column in the L table is empty. So what do I return when say I need to look up L(0,0). I tried to return 0, but that's giving me the wrong encryption.

Artjom B.
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Aditya Agrawal
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  • I would expect that a multiplication by 0 gives 0. So both L and E lookups would be skipped. But the paper only mentions a special case for multiplication by 1 being the identity. – Goswin von Brederlow Feb 20 '18 at 17:25

1 Answers1

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The original action is multiplication. Therefore, if your value is 0x00 you don't have to look it up in the L table, and the result of the whole multiplication is zero.

Idan Gabrielov
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