Polynomial multiplication parity-check matrix
= Polynomial multiplication parity-check matrix
A binary check polynomial $h=\sum_{j=0}^{N-1}h_jX^j$ modulo $X^N+1$ gives the circulant matrix $B_{ti}=h_{t-i\bmod N}$ representing multiplication by $h$. Its kernel is the cyclic code. Selecting independent rows gives a parity-check matrix of rank equal to the redundancy, even when the supplied polynomial is not the canonical check polynomial.
// Target: algebra.bigb