Talk:Finite field arithmetic
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Great minds think alike; I independently wrote almost the same material for Rijndael Galois field. Can you say merge? Samboy 10:59, 29 May 2005 (UTC)
Someone may observe that the material here bears a striking resemblence to some material on my web page. This is because I am allowing the relevant materal on that web page to be released under the GFDL license; there is no copyright violation going on. Keep in mind that I myself can place material form my web page in to articles; however if anyone else copies materials form my web page in to articles, it is a Copyvio. Samboy 20:24, 29 May 2005 (UTC)
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[edit] what?
- By making a logarithm table of the finite field, and performing subtraction in the table. Subtraction of logarithms is the same as division.
this sounds like a brute force attack by an other name, am I wrong?
ADDED BY Paul NO. LOG(A) - LOG(B) = LOG(A/B) Meaning: A/B = EXP(LOG(A) - LOG(B)) Hence factor may be calculated as substraction of LOGs
[edit] Matrix Inversion Example
Can any one help me in finding the multiplicative inverse of 
in GF(24) step-by-step?
[edit] Small oops
I noticed a small oops in the text: > 0x1b corresponds to the irreducible polynomial x8 + x4 + x3 + x + 1.
0x1b is x^4 + x^3 + x + 1. 0x11b (as mentioned int he original Rijndael texts) is the actual polynomial. Since the bit you left off is the x^8 bit it's pointless to add it, but the text itself is still incorrect.
Added by Paul: Yes, this is absolutely pathetic. 0x1b cannot be "x^8 + x^4 + x^3 + x + 1" because "x^8 + x^4 + x^3 + x + 1" was the polynomial that we used for generation of the field. "x^8 + x^4 + x^3 + x + 1" = 0.
[edit] Sum of all field elements
Please see Talk:Field (mathematics)#Sum of all field elements. —The preceding unsigned comment was added by 80.178.241.65 (talk) 20:27, 15 April 2007 (UTC).
[edit] Inadequate description of algorithm
The description of the multiplication is really weird (the description, not the algorithm). It would be easier to understand in pseudocode than in natural language:
- "an eight-bit product p": this is not clear, you should say that the product will be computed in a variable called p;
- "make a copy of a and b...": this is a call to a function with parameter a and b;
etc., every line would be smaller and more meaningful in pseudocode. I cannot understand why someone would write an algorithm in pure natural language. —The preceding unsigned comment was added by 81.247.15.55 (talk) 17:15, 9 May 2007 (UTC).
[edit] Long division edit?
Should there be something else instead of
0100011010
^000000000
in the middle of the long division example? Like the divisor 100011011
Sohannin (talk) 19:19, 30 March 2008 (UTC)
