//***********************************************************************
// Modulo Exponentiation
//***********************************************************************
public BigInteger ModPow(BigInteger exp, BigInteger n)
{
if ((exp.Data[maxLength - 1] & 0x80000000) != 0)
{
throw (new ArithmeticException("Positive exponents only."));
}
BigInteger resultNum = 1;
BigInteger tempNum;
bool thisNegative = false;
if ((this.Data[maxLength - 1] & 0x80000000) != 0) // negative this
{
tempNum = -this % n;
thisNegative = true;
}
else
{
tempNum = this % n; // ensures (tempNum * tempNum) < b^(2k)
}
if ((n.Data[maxLength - 1] & 0x80000000) != 0) // negative n
{
n = -n;
}
// calculate constant = b^(2k) / m
var constant = new BigInteger(0);
int i = n.Length << 1;
constant.Data[i] = 0x00000001;
constant.Length = i + 1;
constant.Divide(n);
//constant /= n;
int totalBits = exp.bitCount();
int count = 0;
var temp = new BigInteger(0);
// perform squaring and multiply exponentiation
for (var pos = 0; pos < exp.Length; pos++)
{
uint mask = 0x01;
//Console.WriteLine("pos = " + pos);
for (var index = 0; index < 32; index++)
{
if ((exp.Data[pos] & mask) != 0)
{
BarrettReduction(ref resultNum, tempNum, n, constant, ref temp);
}
mask <<= 1;
BarrettReduction(ref tempNum, tempNum, n, constant, ref temp);
if (tempNum.Length == 1 && tempNum.Data[0] == 1)
{
if (thisNegative && (exp.Data[0] & 0x1) != 0) //odd exp
{
resultNum.Negative();
}
return(resultNum);
}
count++;
if (count == totalBits)
{
break;
}
}
}
constant.Recycle();
temp.Recycle();
if (thisNegative && (exp.Data[0] & 0x1) != 0) //odd exp
{
resultNum.Negative();
}
return(resultNum);
}
//***********************************************************************
// Modulo Exponentiation
//***********************************************************************
public BigInteger ModPow(BigInteger exp, BigInteger n)
{
if((exp.Data[maxLength-1] & 0x80000000) != 0)
throw (new ArithmeticException("Positive exponents only."));
BigInteger resultNum = 1;
BigInteger tempNum;
bool thisNegative = false;
if((this.Data[maxLength-1] & 0x80000000) != 0) // negative this
{
tempNum = -this % n;
thisNegative = true;
}
else
tempNum = this % n; // ensures (tempNum * tempNum) < b^(2k)
if((n.Data[maxLength-1] & 0x80000000) != 0) // negative n
n = -n;
// calculate constant = b^(2k) / m
var constant = new BigInteger(0);
int i = n.Length << 1;
constant.Data[i] = 0x00000001;
constant.Length = i + 1;
constant.Divide(n);
//constant /= n;
int totalBits = exp.bitCount();
int count = 0;
var temp = new BigInteger(0);
// perform squaring and multiply exponentiation
for(var pos = 0; pos < exp.Length; pos++)
{
uint mask = 0x01;
//Console.WriteLine("pos = " + pos);
for(var index = 0; index < 32; index++)
{
if ((exp.Data[pos] & mask) != 0)
{
BarrettReduction(ref resultNum, tempNum, n, constant, ref temp);
}
mask <<= 1;
BarrettReduction(ref tempNum, tempNum, n, constant, ref temp);
if(tempNum.Length == 1 && tempNum.Data[0] == 1)
{
if(thisNegative && (exp.Data[0] & 0x1) != 0) //odd exp
resultNum.Negative();
return resultNum;
}
count++;
if(count == totalBits)
break;
}
}
constant.Recycle();
temp.Recycle();
if(thisNegative && (exp.Data[0] & 0x1) != 0) //odd exp
resultNum.Negative();
return resultNum;
}
