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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
Posted 8-Feb-12 21:25pm
Edited 14-Feb-12 20:07pm
v5
Comments
SAKryukov at 9-Feb-12 2:30am
   
What, no language tagged, nothing? This is off-topic. Do you need to learn mathematics? Learn it. Matrices is a really simple topics (but of course you will need a lot more). This is a wrong forum.
--SA
Ratika Agarwal at 9-Feb-12 2:40am
   
I think you should do a bit homework on the questions posted in forums. B'coz you may be the only one who is not able to understand some term of it. If you know the ans.then post it. Else, let others help the needy ones.
SAKryukov at 9-Feb-12 2:49am
   
Please do me a favor to decide by myself if I decide to post or not. Please don't take my words as an accusation in poor knowledge in mathematics or something like that. I just don't know it from your question. And to help you, I need to know what exactly you are missing. In this case, do you know the algorithm or not? Is there anything related to computer science or programming you need help with? I still don't understand it. Are you talking about matrix multiplication or something else?
--SA
Ratika Agarwal at 9-Feb-12 2:33am
   
I don't need a language specific answer. I just want its logic and idea. It is a part of advance Mathematics, that's why I have tagged is as mathematics too.
SAKryukov at 9-Feb-12 2:43am
   
Advanced..? He-he... :-)
--SA
Ratika Agarwal at 9-Feb-12 2:47am
   
Quote me... "You are here to ask for help or to help somebody. Not to make fun of what you don't know about."
SAKryukov at 9-Feb-12 2:50am
   
May I ask you why? :-)
You are talking as if this is something bad... :-)
--SA
SAKryukov at 9-Feb-12 3:09am
   
Please, don't post non-solution as a solution. No one will see it anyway unless she or he loads this page, so it could not help you. And you are not answering my questions. Not to many people are dealing with this branch of mathematics anyway, so don't get hysterical. So far, your are the one who gets the most opportunities to find out the solution, but you still expect some help...
--SA
Ratika Agarwal at 9-Feb-12 3:13am
   
What is your ques?? tell me.
SAKryukov at 9-Feb-12 3:19am
   
:-)

1 solution

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Solution 1

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v2
Comments
Ratika Agarwal at 9-Feb-12 2:35am
   
I know matrix operations very well. But my problem is to multiply in GALOIS FIELD(2 power n).
SAKryukov at 9-Feb-12 2:41am
   
Good for you. I apologize then. But what tells you that Galois field requires matrix multiplication which is different. I think matrix multiplication is matrix multiplication. Please explain to me if I'm wrong.
 
And what's your problem? Is it programming or mathematics?
--SA
Ratika Agarwal at 9-Feb-12 2:49am
   
A simple matrix mult.is not same as in Galois Field(2 power n). That is what I am asking here for, how to do it..
SAKryukov at 9-Feb-12 2:55am
   
Sound surprising... do you know just the definition of the operation you need? I don't... "How" goes next...
--SA
SAKryukov at 9-Feb-12 3:12am
   
Is it Vandermonde matrix multiplication over finite field?
--SA
Ratika Agarwal at 9-Feb-12 3:22am
   
Yes. It is the multiplication over a Galois finite Field, but not over vandermonde.
SAKryukov at 9-Feb-12 3:38am
   
I understand what's "over a finite field" but not "over Vandermonde" :-)
--SA
SAKryukov at 9-Feb-12 3:40am
   
OK, where is the definition of a particular operation over a finite field and why you need that operation and not another?
--SA
Ratika Agarwal at 9-Feb-12 3:45am
   
I need this particular operation for "Mix rows /columns operation of AES/Whirlpool algorithms" of cryptography.
SAKryukov at 9-Feb-12 3:53am
   
There are a lot of open-source implementations of this algorithm...
--SA
SAKryukov at 9-Feb-12 3:58am
   
This algorithm is more or less explained here, but I'm afraid, may be not in all detail:
 
http://books.google.com/books?id=WEyWx0k-jLQC&pg=PA43&lpg=PA43&dq=%28finite+OR+Galois%29+field+whirlpool&source=bl&ots=8inQ1kRJ12&sig=thNSa11KdoDqDD8_nwS7pxg9aaI&hl=en&sa=X&ei=uokzT8SNIoKN0QHY7p3IAg&ved=0CCwQ6AEwAQ#v=onepage&q=%28finite%20OR%20Galois%29%20field%20whirlpool&f=false
 
--SA
Ratika Agarwal at 9-Feb-12 3:30am
   
Thanks for help. But I have already searched a lot before coming to code project. I too came across this PDF, but it's not helpful.
SAKryukov at 9-Feb-12 3:37am
   
Yes, that was my guess...
--SA
Espen Harlinn at 9-Feb-12 8:44am
   
5'ed! - quite an effort :)
SAKryukov at 9-Feb-12 12:21pm
   
Not at all, but thank you.
--SA

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