3.I.4G3 . \mathrm{I} . 4 \mathrm{G} \quad

Coding and Cryptography
Part II, 2007

Compute the rank and minimum distance of the cyclic code with generator polynomial g(X)=X3+X+1g(X)=X^{3}+X+1 and parity-check polynomial h(X)=X4+X2+X+1h(X)=X^{4}+X^{2}+X+1. Now let α\alpha be a root of g(X)g(X) in the field with 8 elements. We receive the word r(X)=X5+X3+X(modX71)r(X)=X^{5}+X^{3}+X \quad\left(\bmod X^{7}-1\right). Verify that r(α)=α4r(\alpha)=\alpha^{4}, and hence decode r(X)r(X) using minimum-distance decoding.