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Galois Field GF(2m) Calculator

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Expression for Galois Fiels(2^8) multiplication:-

Which of the following expression is the correct one? please suggest..

Exp[ ( Log A + Log B )Mod 255]

OR

[Exp( Log A + Log B )] Mod 255

Which of the following expression is the correct one? please suggest..

Exp[ ( Log A + Log B )Mod 255]

OR

[Exp( Log A + Log B )] Mod 255

Comments

Comments

thanks. but I do not just want the calculated value.But I need to implement GF(2^8) multiplication for AES Mix Columns Operation. Therefore, to use GF(2^m) and to implement its code is compulsion.

Read more about GF's. Read more theory. Then you will be able to answer yourself. Ask yourself! What should happen when multiplying. Should you get the Exp after Mod, or vice versa.

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Exp have to be done after taking mod of addition.

Exp[ (Log A + Log B) Mod 255].

But Result of addition is so small that it doesn't need Mod, instead, result of Exponent is much long upto 2-4 bytes, which needs Mod.

What should be done in this case??