/* this+=this */
public int dbl()
{
if (INF)
{
return(-1);
}
if (y.iszilch())
{
inf();
return(-1);
}
FP2 w1 = new FP2(x);
FP2 w2 = new FP2(0);
FP2 w3 = new FP2(x);
FP2 w8 = new FP2(x);
w1.sqr();
w8.copy(w1);
w8.imul(3);
w2.copy(y);
w2.sqr();
w3.copy(x);
w3.mul(w2);
w3.imul(4);
w1.copy(w3);
w1.neg();
// w1.norm();
x.copy(w8);
x.sqr();
x.add(w1);
x.add(w1);
x.norm();
z.mul(y);
z.add(z);
w2.add(w2);
w2.sqr();
w2.add(w2);
w3.sub(x);
y.copy(w8);
y.mul(w3);
// w2.norm();
y.sub(w2);
y.norm();
z.norm();
return(1);
}
/* this*=c where c is int */
public void imul(int c)
{
a.imul(c);
b.imul(c);
}
/* Line function */
public static FP12 line(ECP2 A, ECP2 B, FP Qx, FP Qy)
{
ECP2 P = new ECP2();
FP4 a, b, c;
P.copy(A);
FP2 ZZ = new FP2(P.getz());
ZZ.sqr();
int D;
if (A == B)
{
D = A.dbl(); // Check this return value in amcl_ec2.c
}
else
{
D = A.add(B);
}
if (D < 0)
{
return(new FP12(1));
}
FP2 Z3 = new FP2(A.getz());
c = new FP4(0);
if (D == 0)
{ // Addition
FP2 X = new FP2(B.getx());
FP2 Y = new FP2(B.gety());
FP2 T = new FP2(P.getz());
T.mul(Y);
ZZ.mul(T);
FP2 NY = new FP2(P.gety());
NY.neg();
ZZ.add(NY);
Z3.pmul(Qy);
T.mul(P.getx());
X.mul(NY);
T.add(X);
a = new FP4(Z3, T);
ZZ.neg();
ZZ.pmul(Qx);
b = new FP4(ZZ);
}
else
{ // Doubling
FP2 X = new FP2(P.getx());
FP2 Y = new FP2(P.gety());
FP2 T = new FP2(P.getx());
T.sqr();
T.imul(3);
Y.sqr();
Y.add(Y);
Z3.mul(ZZ);
Z3.pmul(Qy);
X.mul(T);
X.sub(Y);
a = new FP4(Z3, X);
T.neg();
ZZ.mul(T);
ZZ.pmul(Qx);
b = new FP4(ZZ);
}
return(new FP12(a, b, c));
}
