31 lines
673 B
C++
31 lines
673 B
C++
|
|
#include "decoding.h"
|
|
|
|
void syndrome_decode (bvector&syndrome, gf2m&fld, polynomial& goppa,
|
|
std::vector<polynomial>& sqInv, bvector&ev)
|
|
|
|
{
|
|
ev.resize (fld.n, 0);
|
|
if (syndrome.zero() ) return;
|
|
|
|
polynomial p;
|
|
syndrome.to_poly (p, fld);
|
|
p.inv (goppa, fld); // p=S^-1 mod goppa
|
|
|
|
p[1] = fld.add (1, p[1]); //p is now tau
|
|
p.sqrt (sqInv, fld); //tau = sqrt(T+x) mod goppa
|
|
|
|
polynomial a, b;
|
|
p.mod_to_fracton (a, b, goppa, fld);
|
|
a.square (fld);
|
|
b.square (fld);
|
|
b.shift (1);
|
|
a.add (b, fld); //new a = a^2 + x b^2
|
|
|
|
a.make_monic (fld); //now it is the error locator.
|
|
|
|
for (uint i = 0; i < fld.n; ++i) {
|
|
if (0 == a.eval (i, fld) ) ev[i] = 1;
|
|
}
|
|
}
|