Linked Questions
12 questions linked to/from Multiplicative inverse in $\operatorname{GF}(2^8)$?
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How to do Hexadecimal multiplication in GF(2^8)
I'm trying to do a hexadecimal multiplication in GF(2^8).
Now, I know the technique of shifting left the binary numbers in some cases, for example:
02 * 9E
0000 0010 * 1001 1110
you shift one time ...
5
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2
answers
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Efficient pen-and-paper calculation of the Galois Field multiplication?
I have been reading on multiplication over GF for the Inverse Matrix Step in AES, and I feel like converting the hex numbers to binary, multiplying them and then doing the modifications required for ...
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multiplicative inverse [duplicate]
I actually do want to know how to generate the multiplication inverse (M.I) table, I mean the calculation how the M.I been generated.. such as the M.I of 22 is 5A regarding to the table.. Do you know ...
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Multiplication/Division in Galois Field (2^8)
I'm attempting to implement multiplication and division in $GF(2^8)$ using log and exponential tables. I'm using the exponent of 3 as my generator, using instructions from here.
However I'm having ...
4
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1
answer
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Itoh Tsuji algorithm
I'd like to use the Itoh-Tsujii algorithm for a dynamic substitution table, but I do not get the following line:
$$r\ \gets\ (p^m - 1)\,/\,(p - 1)$$
And why can $r$ be used to calculate the ...
3
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1
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How are calculated numbers in AES S-box?
I have a problem calculating the 0x02 value of the AES S-Box.
I followed the steps descibed in “How are the AES S-Boxes calculated?”, but my answer is not correct.
...
2
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1
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How are Rijndael's S-Boxes generated?
Wikipedia: Rijndael's Forward S-box
I'm writing C Code to generate S-boxes but I'm stuck.
Would you mind explaining one entry of the S-box? (say for x = 0x2). ...
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1
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Inversion in $GF(2^8)$ AES [duplicate]
I was wondering how you would calculate the S-box in AES. I found that you have to calculate the inverse of the polynomials in $GF(2^8)$. I found out that to calculate the inverse, you have to use the ...
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1
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Calculating the multiplicative inverse of a number in $GF(2^n)$ where $n > 8$
Suppose that:
We have a polynomial $g(x)$ of degree $n$.
$n > 8$.
$q$ is the multiplicative inverse of $p$ in $G(2^n)$ modulo $g(x)$. If $p = 0$, then $q = 0$.
This could be used:
As a non-...
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1
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Multiplicative Inverse in AES [duplicate]
I want to calculate the S-box for AES. But I have a problem with the multiplicative inverse step. For example, the inverse of 95 is ...
1
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0
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How to find multiplicative inverse of a hexadecimal number in the finite field GF(2^8)? [duplicate]
I am new to cryptography. As I was reading a note regarding S-box construction, I found a step mentioning multiplicative inverse of a number in the finite field GF(2^8). I couldn't understand it!! Can ...
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Calculating the inverse for a Rijndael s-box [duplicate]
I want to calculate a Rijndael S-box but something went wrong. How can I calculate the inverse? In the following is my approach:
given:
$f(x)=x^8+x^4+x^3+x+1 \rightarrow$ binary: 100011011
0x12 = ...