public WEC3n(GF3nElement a, GF3nElement b, GF3nElement c) {
if (!(a.getFiniteField().equals(b.getFiniteField())
|| b.getFiniteField().equals(c.getFiniteField())))
throw new InvalidParameterException("coefficients are not in the same finite field");
this.a = new GF3nElement(a);
this.b = new GF3nElement(b);
this.c = new GF3nElement(c);
}
@Override
public boolean isSingular() {
if (a.isZero() && b.isZero()) return false;
else if (!(a.isZero() || b.isZero())) {
try {
GF3nElement x = a.invert().multiply(b);
if (x.cube().sum(x.multiply(b).negate()).sum(c).isZero()) return false;
else return true;
} catch (NoCommonFiniteFieldException | NotInFiniteFieldException e) {
// This shouldn't happen never
e.printStackTrace();
return false;
}
} else return true;
}
public HEC3n toHessian() {
if (this.isSupersingular() && !this.a.equals(this.a.getFiniteField().one()))
throw new InvalidParameterException(
"Elliptic curve must be ordinary and the quadratic coefficient must be 1.");
try {
GF3nElement x = a.invert().multiply(b);
GF3nElement newC = x.cube().sum(x.multiply(b).negate()).sum(c);
int n = this.a.getFiniteField().getExtensionDegree();
for (int i = 1; i < n; i++) newC = newC.cube();
newC = newC.invert().negate();
return new HEC3n(newC);
} catch (NoCommonFiniteFieldException | NotInFiniteFieldException e) {
// This shouldn't happen never
e.printStackTrace();
return null;
}
}