public void BarrettReduction(BigInteger x)
{
BigInteger n = mod;
uint k = n.length,
kPlusOne = k + 1,
kMinusOne = k - 1;
// x < mod, so nothing to do.
if (x.length < k) return;
BigInteger q3;
//
// Validate pointers
//
if (x.data.Length < x.length) throw new IndexOutOfRangeException("x out of range");
// q1 = x / b^ (k-1)
// q2 = q1 * constant
// q3 = q2 / b^ (k+1), Needs to be accessed with an offset of kPlusOne
// TODO: We should the method in HAC p 604 to do this (14.45)
q3 = new BigInteger(Sign.Positive, x.length - kMinusOne + constant.length);
Kernel.Multiply(x.data, kMinusOne, x.length - kMinusOne, constant.data, 0, constant.length, q3.data, 0);
// r1 = x mod b^ (k+1)
// i.e. keep the lowest (k+1) words
uint lengthToCopy = (x.length > kPlusOne) ? kPlusOne : x.length;
x.length = lengthToCopy;
x.Normalize();
// r2 = (q3 * n) mod b^ (k+1)
// partial multiplication of q3 and n
BigInteger r2 = new BigInteger(Sign.Positive, kPlusOne);
Kernel.MultiplyMod2p32pmod(q3.data, (int)kPlusOne, (int)q3.length - (int)kPlusOne, n.data, 0, (int)n.length, r2.data, 0, (int)kPlusOne);
r2.Normalize();
if (r2 <= x)
{
Kernel.MinusEq(x, r2);
}
else
{
BigInteger val = new BigInteger(Sign.Positive, kPlusOne + 1);
val.data[kPlusOne] = 0x00000001;
Kernel.MinusEq(val, r2);
Kernel.PlusEq(x, val);
}
while (x >= n)
Kernel.MinusEq(x, n);
}
public static BigInteger operator *(BigInteger bi1, BigInteger bi2)
{
if (bi1 == 0 || bi2 == 0) return 0;
//
// Validate pointers
//
if (bi1.data.Length < bi1.length) throw new IndexOutOfRangeException("bi1 out of range");
if (bi2.data.Length < bi2.length) throw new IndexOutOfRangeException("bi2 out of range");
BigInteger ret = new BigInteger(Sign.Positive, bi1.length + bi2.length);
Kernel.Multiply(bi1.data, 0, bi1.length, bi2.data, 0, bi2.length, ret.data, 0);
ret.Normalize();
return ret;
}
/// <summary>
/// Generates a new, random BigInteger of the specified length.
/// </summary>
/// <param name="bits">The number of bits for the new number.</param>
/// <param name="rng">A random number generator to use to obtain the bits.</param>
/// <returns>A random number of the specified length.</returns>
public static BigInteger GenerateRandom(int bits, RandomNumberGenerator rng)
{
int dwords = bits >> 5;
int remBits = bits & 0x1F;
if (remBits != 0)
dwords++;
BigInteger ret = new BigInteger(Sign.Positive, (uint)dwords + 1);
byte[] random = new byte[dwords << 2];
rng.GetBytes(random);
Buffer.BlockCopy(random, 0, ret.data, 0, (int)dwords << 2);
if (remBits != 0)
{
uint mask = (uint)(0x01 << (remBits - 1));
ret.data[dwords - 1] |= mask;
mask = (uint)(0xFFFFFFFF >> (32 - remBits));
ret.data[dwords - 1] &= mask;
}
else
ret.data[dwords - 1] |= 0x80000000;
ret.Normalize();
return ret;
}
public static BigInteger RightShift(BigInteger bi, int n)
{
if (n == 0) return new BigInteger(bi);
int w = n >> 5;
int s = n & ((1 << 5) - 1);
BigInteger ret = new BigInteger(Sign.Positive, bi.length - (uint)w + 1);
uint l = (uint)ret.data.Length - 1;
if (s != 0)
{
uint x, carry = 0;
while (l-- > 0)
{
x = bi.data[l + w];
ret.data[l] = (x >> n) | carry;
carry = x << (32 - n);
}
}
else
{
while (l-- > 0)
ret.data[l] = bi.data[l + w];
}
ret.Normalize();
return ret;
}
public static BigInteger MultiplyByDword(BigInteger n, uint f)
{
BigInteger ret = new BigInteger(Sign.Positive, n.length + 1);
uint i = 0;
ulong c = 0;
do
{
c += (ulong)n.data[i] * (ulong)f;
ret.data[i] = (uint)c;
c >>= 32;
} while (++i < n.length);
ret.data[i] = (uint)c;
ret.Normalize();
return ret;
}
public static BigInteger[] multiByteDivide(BigInteger bi1, BigInteger bi2)
{
if (Kernel.Compare(bi1, bi2) == Sign.Negative)
return new BigInteger[2] { 0, new BigInteger(bi1) };
bi1.Normalize(); bi2.Normalize();
if (bi2.length == 1)
return DwordDivMod(bi1, bi2.data[0]);
uint remainderLen = bi1.length + 1;
int divisorLen = (int)bi2.length + 1;
uint mask = 0x80000000;
uint val = bi2.data[bi2.length - 1];
int shift = 0;
int resultPos = (int)bi1.length - (int)bi2.length;
while (mask != 0 && (val & mask) == 0)
{
shift++; mask >>= 1;
}
BigInteger quot = new BigInteger(Sign.Positive, bi1.length - bi2.length + 1);
BigInteger rem = (bi1 << shift);
uint[] remainder = rem.data;
bi2 = bi2 << shift;
int j = (int)(remainderLen - bi2.length);
int pos = (int)remainderLen - 1;
uint firstDivisorByte = bi2.data[bi2.length - 1];
ulong secondDivisorByte = bi2.data[bi2.length - 2];
while (j > 0)
{
ulong dividend = ((ulong)remainder[pos] << 32) + (ulong)remainder[pos - 1];
ulong q_hat = dividend / (ulong)firstDivisorByte;
ulong r_hat = dividend % (ulong)firstDivisorByte;
do
{
if (q_hat == 0x100000000 ||
(q_hat * secondDivisorByte) > ((r_hat << 32) + remainder[pos - 2]))
{
q_hat--;
r_hat += (ulong)firstDivisorByte;
if (r_hat < 0x100000000)
continue;
}
break;
} while (true);
//
// At this point, q_hat is either exact, or one too large
// (more likely to be exact) so, we attempt to multiply the
// divisor by q_hat, if we get a borrow, we just subtract
// one from q_hat and add the divisor back.
//
uint t;
uint dPos = 0;
int nPos = pos - divisorLen + 1;
ulong mc = 0;
uint uint_q_hat = (uint)q_hat;
do
{
mc += (ulong)bi2.data[dPos] * (ulong)uint_q_hat;
t = remainder[nPos];
remainder[nPos] -= (uint)mc;
mc >>= 32;
if (remainder[nPos] > t) mc++;
dPos++; nPos++;
} while (dPos < divisorLen);
nPos = pos - divisorLen + 1;
dPos = 0;
// Overestimate
if (mc != 0)
{
uint_q_hat--;
ulong sum = 0;
do
{
sum = ((ulong)remainder[nPos]) + ((ulong)bi2.data[dPos]) + sum;
remainder[nPos] = (uint)sum;
sum >>= 32;
dPos++; nPos++;
} while (dPos < divisorLen);
}
quot.data[resultPos--] = (uint)uint_q_hat;
pos--;
j--;
}
quot.Normalize();
rem.Normalize();
BigInteger[] ret = new BigInteger[2] { quot, rem };
if (shift != 0)
ret[1] >>= shift;
return ret;
}
public static BigInteger LeftShift(BigInteger bi, int n)
{
if (n == 0) return new BigInteger(bi, bi.length + 1);
int w = n >> 5;
n &= ((1 << 5) - 1);
BigInteger ret = new BigInteger(Sign.Positive, bi.length + 1 + (uint)w);
uint i = 0, l = bi.length;
if (n != 0)
{
uint x, carry = 0;
while (i < l)
{
x = bi.data[i];
ret.data[i + w] = (x << n) | carry;
carry = x >> (32 - n);
i++;
}
ret.data[i + w] = carry;
}
else
{
while (i < l)
{
ret.data[i + w] = bi.data[i];
i++;
}
}
ret.Normalize();
return ret;
}
/// <summary>
/// Performs n / d and n % d in one operation.
/// </summary>
/// <param name="n">A BigInteger, upon exit this will hold n / d</param>
/// <param name="d">The divisor</param>
/// <returns>n % d</returns>
public static uint SingleByteDivideInPlace(BigInteger n, uint d)
{
ulong r = 0;
uint i = n.length;
while (i-- > 0)
{
r <<= 32;
r |= n.data[i];
n.data[i] = (uint)(r / d);
r %= d;
}
n.Normalize();
return (uint)r;
}
public static BigInteger[] DwordDivMod(BigInteger n, uint d)
{
BigInteger ret = new BigInteger(Sign.Positive, n.length);
ulong r = 0;
uint i = n.length;
while (i-- > 0)
{
r <<= 32;
r |= n.data[i];
ret.data[i] = (uint)(r / d);
r %= d;
}
ret.Normalize();
BigInteger rem = (uint)r;
return new BigInteger[] { ret, rem };
}
public static void PlusEq(BigInteger bi1, BigInteger bi2)
{
uint[] x, y;
uint yMax, xMax, i = 0;
bool flag = false;
// x should be bigger
if (bi1.length < bi2.length)
{
flag = true;
x = bi2.data;
xMax = bi2.length;
y = bi1.data;
yMax = bi1.length;
}
else
{
x = bi1.data;
xMax = bi1.length;
y = bi2.data;
yMax = bi2.length;
}
uint[] r = bi1.data;
ulong sum = 0;
// Add common parts of both numbers
do
{
sum += ((ulong)x[i]) + ((ulong)y[i]);
r[i] = (uint)sum;
sum >>= 32;
} while (++i < yMax);
// Copy remainder of longer number while carry propagation is required
bool carry = (sum != 0);
if (carry)
{
if (i < xMax)
{
do
carry = ((r[i] = x[i] + 1) == 0);
while (++i < xMax && carry);
}
if (carry)
{
r[i] = 1;
bi1.length = ++i;
return;
}
}
// Copy the rest
if (flag && i < xMax - 1)
{
do
r[i] = x[i];
while (++i < xMax);
}
bi1.length = xMax + 1;
bi1.Normalize();
}
public static BigInteger Subtract(BigInteger big, BigInteger small)
{
BigInteger result = new BigInteger(Sign.Positive, big.length);
uint[] r = result.data, b = big.data, s = small.data;
uint i = 0, c = 0;
do
{
uint x = s[i];
if (((x += c) < c) | ((r[i] = b[i] - x) > ~x))
c = 1;
else
c = 0;
} while (++i < small.length);
if (i == big.length) goto fixup;
if (c == 1)
{
do
r[i] = b[i] - 1;
while (b[i++] == 0 && i < big.length);
if (i == big.length) goto fixup;
}
do
r[i] = b[i];
while (++i < big.length);
fixup:
result.Normalize();
return result;
}
/// <summary>
/// Adds two numbers with the same sign.
/// </summary>
/// <param name="bi1">A BigInteger</param>
/// <param name="bi2">A BigInteger</param>
/// <returns>bi1 + bi2</returns>
public static BigInteger AddSameSign(BigInteger bi1, BigInteger bi2)
{
uint[] x, y;
uint yMax, xMax, i = 0;
// x should be bigger
if (bi1.length < bi2.length)
{
x = bi2.data;
xMax = bi2.length;
y = bi1.data;
yMax = bi1.length;
}
else
{
x = bi1.data;
xMax = bi1.length;
y = bi2.data;
yMax = bi2.length;
}
BigInteger result = new BigInteger(Sign.Positive, xMax + 1);
uint[] r = result.data;
ulong sum = 0;
// Add common parts of both numbers
do
{
sum = ((ulong)x[i]) + ((ulong)y[i]) + sum;
r[i] = (uint)sum;
sum >>= 32;
} while (++i < yMax);
// Copy remainder of longer number while carry propagation is required
bool carry = (sum != 0);
if (carry)
{
if (i < xMax)
{
do
carry = ((r[i] = x[i] + 1) == 0);
while (++i < xMax && carry);
}
if (carry)
{
r[i] = 1;
result.length = ++i;
return result;
}
}
// Copy the rest
if (i < xMax)
{
do
r[i] = x[i];
while (++i < xMax);
}
result.Normalize();
return result;
}
public static BigInteger ToMont(BigInteger n, BigInteger m)
{
n.Normalize(); m.Normalize();
n <<= (int)m.length * 32;
n %= m;
return n;
}
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 b
//
do
{
//
// r = r ^ 2 % m
//
Kernel.SquarePositive(resultNum, ref wkspace);
if (!(resultNum.length < mod.length))
BarrettReduction(resultNum);
if (exp.TestBit(pos))
{
//
// r = r * b % 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;
}