private BigInteger OddPow( BigInteger b, BigInteger exp )
{
BigInteger resultNum = new BigInteger(Montgomery.ToMont(1, mod), mod.length << 1);
BigInteger tempNum = new BigInteger(Montgomery.ToMont(b, mod), mod.length << 1); // ensures (tempNum * tempNum) < m^ (2k)
uint mPrime = Montgomery.Inverse(mod.data[0]);
uint totalBits = ( uint )exp.BitCount();
uint[] wkspace = new uint[mod.length << 1];
// perform squaring and multiply exponentiation
for ( uint pos = 0; pos < totalBits; pos++ )
{
if ( exp.TestBit(pos) )
{
Array.Clear(wkspace, 0, wkspace.Length);
Kernel.Multiply(resultNum.data, 0, resultNum.length, tempNum.data, 0, tempNum.length, wkspace, 0);
resultNum.length += tempNum.length;
uint[] t = wkspace;
wkspace = resultNum.data;
resultNum.data = t;
Montgomery.Reduce(resultNum, mod, mPrime);
}
Kernel.SquarePositive(tempNum, ref wkspace);
Montgomery.Reduce(tempNum, mod, mPrime);
}
Montgomery.Reduce(resultNum, mod, mPrime);
return resultNum;
}
private unsafe BigInteger EvenPow( uint b, BigInteger exp )
{
exp.Normalize();
uint[] wkspace = new uint[mod.length << 1 + 1];
BigInteger resultNum = new BigInteger(( BigInteger )b, mod.length << 1 + 1);
uint pos = ( uint )exp.BitCount() - 2;
//
// We know that the first itr will make the val m
//
do
{
//
// r = r ^ 2 % m
//
Kernel.SquarePositive(resultNum, ref wkspace);
if ( !( resultNum.length < mod.length ) )
BarrettReduction(resultNum);
if ( exp.TestBit(pos) )
{
//
// r = r * m % m
//
// TODO: Is Unsafe really speeding things up?
fixed ( uint* u = resultNum.data )
{
uint i = 0;
ulong mc = 0;
do
{
mc += ( ulong )u[i] * ( ulong )b;
u[i] = ( uint )mc;
mc >>= 32;
} while ( ++i < resultNum.length );
if ( resultNum.length < mod.length )
{
if ( mc != 0 )
{
u[i] = ( uint )mc;
resultNum.length++;
while ( resultNum >= mod )
Kernel.MinusEq(resultNum, mod);
}
}
else if ( mc != 0 )
{
//
// First, we estimate the quotient by dividing
// the first part of each of the numbers. Then
// we correct this, if necessary, with a subtraction.
//
uint cc = ( uint )mc;
// We would rather have this estimate overshoot,
// so we add one to the divisor
uint divEstimate = ( uint )( ( ( ( ulong )cc << 32 ) | ( ulong )u[i - 1] ) /
( mod.data[mod.length - 1] + 1 ) );
uint t;
i = 0;
mc = 0;
do
{
mc += ( ulong )mod.data[i] * ( ulong )divEstimate;
t = u[i];
u[i] -= ( uint )mc;
mc >>= 32;
if ( u[i] > t )
mc++;
i++;
} while ( i < resultNum.length );
cc -= ( uint )mc;
if ( cc != 0 )
{
uint sc = 0, j = 0;
uint[] s = mod.data;
do
{
uint a = s[j];
if ( ( ( a += sc ) < sc ) | ( ( u[j] -= a ) > ~a ) )
sc = 1;
else
sc = 0;
j++;
} while ( j < resultNum.length );
cc -= sc;
}
while ( resultNum >= mod )
Kernel.MinusEq(resultNum, mod);
}
else
{
while ( resultNum >= mod )
Kernel.MinusEq(resultNum, mod);
}
}
}
} while ( pos-- > 0 );
return resultNum;
}
public BigInteger EvenPow( BigInteger b, BigInteger exp )
{
BigInteger resultNum = new BigInteger(( BigInteger )1, mod.length << 1);
BigInteger tempNum = new BigInteger(b % mod, mod.length << 1); // ensures (tempNum * tempNum) < m^ (2k)
uint totalBits = ( uint )exp.BitCount();
uint[] wkspace = new uint[mod.length << 1];
// perform squaring and multiply exponentiation
for ( uint pos = 0; pos < totalBits; pos++ )
{
if ( exp.TestBit(pos) )
{
Array.Clear(wkspace, 0, wkspace.Length);
Kernel.Multiply(resultNum.data, 0, resultNum.length, tempNum.data, 0, tempNum.length, wkspace, 0);
resultNum.length += tempNum.length;
uint[] t = wkspace;
wkspace = resultNum.data;
resultNum.data = t;
BarrettReduction(resultNum);
}
Kernel.SquarePositive(tempNum, ref wkspace);
BarrettReduction(tempNum);
if ( tempNum == 1 )
{
return resultNum;
}
}
return resultNum;
}
