/* this*=c mod Modulus, where c is a small int */
public void imul(int c)
{
norm();
bool s = false;
if (c < 0)
{
c = -c;
s = true;
}
long afx = (BIG.EXCESS(x) + 1) * (c + 1) + 1;
if (c < ROM.NEXCESS && afx < ROM.FEXCESS)
{
x.imul(c);
}
else
{
if (afx < ROM.FEXCESS)
{
x.pmul(c);
}
else
{
DBIG d = x.pxmul(c);
x.copy(d.mod(p));
}
}
if (s)
{
neg();
}
norm();
}
/* r=ck^a.cl^n using XTR double exponentiation method on traces of FP12s. See Stam thesis. */
public FP4 xtr_pow2(FP4 ck, FP4 ckml, FP4 ckm2l, BIG a, BIG b)
{
a.norm();
b.norm();
BIG e = new BIG(a);
BIG d = new BIG(b);
BIG w = new BIG(0);
FP4 cu = new FP4(ck); // can probably be passed in w/o copying
FP4 cv = new FP4(this);
FP4 cumv = new FP4(ckml);
FP4 cum2v = new FP4(ckm2l);
FP4 r = new FP4(0);
FP4 t = new FP4(0);
int f2 = 0;
while (d.parity() == 0 && e.parity() == 0)
{
d.fshr(1);
e.fshr(1);
f2++;
}
while (BIG.comp(d, e) != 0)
{
if (BIG.comp(d, e) > 0)
{
w.copy(e);
w.imul(4);
w.norm();
if (BIG.comp(d, w) <= 0)
{
w.copy(d);
d.copy(e);
e.rsub(w);
e.norm();
t.copy(cv);
t.xtr_A(cu, cumv, cum2v);
cum2v.copy(cumv);
cum2v.conj();
cumv.copy(cv);
cv.copy(cu);
cu.copy(t);
}
else if (d.parity() == 0)
{
d.fshr(1);
r.copy(cum2v);
r.conj();
t.copy(cumv);
t.xtr_A(cu, cv, r);
cum2v.copy(cumv);
cum2v.xtr_D();
cumv.copy(t);
cu.xtr_D();
}
else if (e.parity() == 1)
{
d.sub(e);
d.norm();
d.fshr(1);
t.copy(cv);
t.xtr_A(cu, cumv, cum2v);
cu.xtr_D();
cum2v.copy(cv);
cum2v.xtr_D();
cum2v.conj();
cv.copy(t);
}
else
{
w.copy(d);
d.copy(e);
d.fshr(1);
e.copy(w);
t.copy(cumv);
t.xtr_D();
cumv.copy(cum2v);
cumv.conj();
cum2v.copy(t);
cum2v.conj();
t.copy(cv);
t.xtr_D();
cv.copy(cu);
cu.copy(t);
}
}
if (BIG.comp(d, e) < 0)
{
w.copy(d);
w.imul(4);
w.norm();
if (BIG.comp(e, w) <= 0)
{
e.sub(d);
e.norm();
t.copy(cv);
t.xtr_A(cu, cumv, cum2v);
cum2v.copy(cumv);
cumv.copy(cu);
cu.copy(t);
}
else if (e.parity() == 0)
{
w.copy(d);
d.copy(e);
d.fshr(1);
e.copy(w);
t.copy(cumv);
t.xtr_D();
cumv.copy(cum2v);
cumv.conj();
cum2v.copy(t);
cum2v.conj();
t.copy(cv);
t.xtr_D();
cv.copy(cu);
cu.copy(t);
}
else if (d.parity() == 1)
{
w.copy(e);
e.copy(d);
w.sub(d);
w.norm();
d.copy(w);
d.fshr(1);
t.copy(cv);
t.xtr_A(cu, cumv, cum2v);
cumv.conj();
cum2v.copy(cu);
cum2v.xtr_D();
cum2v.conj();
cu.copy(cv);
cu.xtr_D();
cv.copy(t);
}
else
{
d.fshr(1);
r.copy(cum2v);
r.conj();
t.copy(cumv);
t.xtr_A(cu, cv, r);
cum2v.copy(cumv);
cum2v.xtr_D();
cumv.copy(t);
cu.xtr_D();
}
}
}
r.copy(cv);
r.xtr_A(cu, cumv, cum2v);
for (int i = 0; i < f2; i++)
{
r.xtr_D();
}
r = r.xtr_pow(d);
return(r);
}
