/* Convert to Hex String */
public override string ToString()
{
BIG b;
string s = "";
int len = NBits();
if (len % 4 == 0)
{
len /= 4;
}
else
{
len /= 4;
len++;
}
if (len < MODBYTES * 2)
{
len = MODBYTES * 2;
}
for (int i = len - 1; i >= 0; i--)
{
b = new BIG(this);
b.Shr(i * 4);
s += (b.w[0] & 15).ToString("x");
}
return(s);
}
/* Jacobi Symbol (this/p). Returns 0, 1 or -1 */
public virtual int Jacobi(BIG p)
{
int n8, k, m = 0;
BIG t = new BIG(0);
BIG x = new BIG(0);
BIG n = new BIG(0);
BIG zilch = new BIG(0);
BIG one = new BIG(1);
if (p.Parity() == 0 || Comp(this, zilch) == 0 || Comp(p, one) <= 0)
{
return(0);
}
Norm();
x.Copy(this);
n.Copy(p);
x.Mod(p);
while (Comp(n, one) > 0)
{
if (Comp(x, zilch) == 0)
{
return(0);
}
n8 = n.LastBits(3);
k = 0;
while (x.Parity() == 0)
{
k++;
x.Shr(1);
}
if (k % 2 == 1)
{
m += (n8 * n8 - 1) / 8;
}
m += (n8 - 1) * (x.LastBits(2) - 1) / 4;
t.Copy(n);
t.Mod(x);
n.Copy(x);
x.Copy(t);
m %= 2;
}
if (m == 0)
{
return(1);
}
else
{
return(-1);
}
}
/* a=1/a mod 2^256. This is very fast! */
public virtual void InvMod2m()
{
int i;
BIG U = new BIG(0);
BIG b = new BIG(0);
BIG c = new BIG(0);
U.Inc(InvMod256(LastBits(8)));
for (i = 8; i < BIGBITS; i <<= 1)
{
U.Norm();
b.Copy(this);
b.Mod2m(i);
BIG t1 = SMul(U, b);
t1.Shr(i);
c.Copy(this);
c.Shr(i);
c.Mod2m(i);
BIG t2 = SMul(U, c);
t2.Mod2m(i);
t1.Add(t2);
t1.Norm();
b = SMul(t1, U);
t1.Copy(b);
t1.Mod2m(i);
t2.One();
t2.Shl(i);
t1.RSub(t2);
t1.Norm();
t1.Shl(i);
U.Add(t1);
}
U.Mod2m(BIGBITS);
Copy(U);
Norm();
}