ec_curve *ec_binproj(field *f, mp *a, mp *b)
{
ecctx_bin *cc = CREATE(ecctx_bin);
+ int i;
+ mp *c, *d;
+
cc->c.ops = &ec_binprojops;
cc->c.f = f;
cc->c.a = F_IN(f, MP_NEW, a);
cc->c.b = F_IN(f, MP_NEW, b);
- cc->bb = F_SQRT(f, MP_NEW, cc->c.b);
- if (cc->bb)
- cc->bb = F_SQRT(f, cc->bb, cc->bb);
- if (!cc->bb) {
+
+ c = MP_COPY(cc->c.b);
+ for (i = 0; i < f->nbits - 2; i++)
+ c = F_SQR(f, c, c);
+ d = F_SQR(f, MP_NEW, c); d = F_SQR(f, d, d);
+ if (!MP_EQ(d, cc->c.b)) {
+ MP_DROP(c);
+ MP_DROP(d);
MP_DROP(cc->c.a);
MP_DROP(cc->c.b);
DESTROY(cc);
return (0);
}
+ cc->bb = c;
+ MP_DROP(d);
return (&cc->c);
}