/* Line function */
static void PAIR_line(FP12 *v,ECP2 *A,ECP2 *B,BIG Qx,BIG Qy)
{
ECP2 P;
FP2 Z3,X,Y,ZZ,T,NY;
FP4 a,b,c;
int D;
ECP2_copy(&P,A);
if (A==B)
D=ECP2_dbl(A); // check these return numbers...
else
D=ECP2_add(A,B);
if (D<0)
{ /* Infinity */
FP12_one(v);
return;
}
FP2_copy(&Z3,&(A->z));
FP4_zero(&c);
FP2_sqr(&ZZ,&(P.z)); /* ZZ=Z^2 */
if (D==0)
{ /* addition */
ECP2_get(&X,&Y,B);
FP2_mul(&T,&(P.z),&Y); /* T=Z*Y2 */
FP2_mul(&ZZ,&ZZ,&T);
FP2_neg(&NY,&(P.y));
FP2_add(&ZZ,&ZZ,&NY); /* ZZ=Z^3*Y2-Y (slope numerator) */
FP2_pmul(&Z3,&Z3,Qy); /* Z3*Qy */
FP2_mul(&T,&T,&(P.x));
FP2_mul(&X,&X,&NY);
FP2_add(&T,&T,&X); /* Z*Y2*X-X2*Y */
FP4_from_FP2s(&a,&Z3,&T); /* a=[Z3*Qy,Z*Y2*X-X2*Y] */
FP2_neg(&ZZ,&ZZ);
FP2_pmul(&ZZ,&ZZ,Qx);
FP4_from_FP2(&b,&ZZ); /* b=-slope*Qx */
}
else
{ /* doubling */
FP2_sqr(&T,&(P.x));
FP2_imul(&T,&T,3); /* T=3X^2 (slope numerator) */
FP2_sqr(&Y,&(P.y));
FP2_add(&Y,&Y,&Y); /* Y=2Y^2 */
FP2_mul(&Z3,&Z3,&ZZ); /* Z3=Z3*ZZ */
FP2_pmul(&Z3,&Z3,Qy); /* Z3=Z3*ZZ*Qy */
FP2_mul(&X,&(P.x),&T);
FP2_sub(&X,&X,&Y); /* X=X*slope-2Y^2 */
FP4_from_FP2s(&a,&Z3,&X); /* a=[Z3*ZZ*Qy , X*slope-2Y^2] */
FP2_neg(&T,&T);
FP2_mul(&ZZ,&ZZ,&T);
FP2_pmul(&ZZ,&ZZ,Qx);
FP4_from_FP2(&b,&ZZ); /* b=-slope*ZZ*Qx */
}
FP12_from_FP4s(v,&a,&b,&c);
}
/* Set w=s*x, where s is int */
void FP4_imul(FP4 *w,FP4 *x,int s)
{
FP2_imul(&(w->a),&(x->a),s);
FP2_imul(&(w->b),&(x->b),s);
}
