Thursday, 25 September 2014

linear algebra - Primitive elements of GF(8)



I'm trying to find the primitive elements of $GF(8),$ the minimal polynomials of all elements of $GF(8)$ and their roots, and calculate the powers of $\alpha^i$ for $x^3 + x + 1.$




If I did my math correct, I found the minimal polynomials to be $x, x + 1, x^3 + x + 1,$ and $x^3 + x^2 + 1,$ and the primitive elements to be $\alpha, \dots, \alpha^6 $



Would the powers of $\alpha^i$ as a polynomial (of degree at most two) be: $\alpha, \alpha^2, \alpha+ 1, \alpha^2 + \alpha, \alpha^2 + \alpha + 1,$ and $\alpha^2 + 1$?



Am I on the right track?


Answer



Those are all correct. Here's everything presented in a table:



$$\begin{array}{lll}
\textbf{element} & \textbf{reduced} & \textbf{min poly} \\

0 & 0 & x \\
\alpha^0 & 1 & x+1 \\
\alpha^1 & \alpha & x^3+x+1 \\
\alpha^2 & \alpha^2 & x^3+x+1 \\
\alpha^3 & \alpha+1 & x^3+x^2+1 \\
\alpha^4 & \alpha^2+\alpha & x^3+x+1 \\
\alpha^5 & \alpha^2+\alpha+1 & x^3 + x^2 + 1 \\
\alpha^6 & \alpha^2+1 & x^3 + x^2 + 1 \\
\end{array}$$


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