/// <summary>
/// Construct a random GF2Vector of the given length with the specified number of non-zero coefficients
/// </summary>
///
/// <param name="Length">The length of the vector</param>
/// <param name="T">The number of non-zero coefficients</param>
/// <param name="SecRnd">The source of randomness</param>
public GF2Vector(int Length, int T, IRandom SecRnd)
{
if (T > Length)
{
throw new ArithmeticException("The hamming weight is greater than the length of vector.");
}
this.Length = Length;
int size = (Length + 31) >> 5;
m_elements = new int[size];
int[] help = new int[Length];
for (int i = 0; i < Length; i++)
{
help[i] = i;
}
int m = Length;
for (int i = 0; i < T; i++)
{
int j = RandomDegree.NextInt(SecRnd, m);
SetBit(help[j]);
m--;
help[j] = help[m];
}
}
/// <summary>
/// Create a random permutation of the given size
/// </summary>
///
/// <param name="N">The size of the permutation</param>
/// <param name="SecRnd">The source of randomness</param>
public Permutation(int N, IRandom SecRnd)
{
if (N <= 0)
{
throw new ArgumentException("Permutation: Invalid length!");
}
m_perm = new int[N];
int[] help = new int[N];
for (int i = 0; i < N; i++)
{
help[i] = i;
}
int k = N;
for (int j = 0; j < N; j++)
{
int i = RandomDegree.NextInt(SecRnd, k);
k--;
m_perm[j] = help[i];
help[i] = help[k];
}
}
/// <summary>
/// Create a random non-zero field element
/// </summary>
///
/// <param name="SecRnd">The IRandom instance</param>
///
/// <returns>A random non zero element</returns>
public int GetRandomNonZeroElement(IRandom SecRnd)
{
int controltime = 1 << 20;
int count = 0;
int result = RandomDegree.NextInt(SecRnd, 1 << m_degree);
while ((result == 0) && (count < controltime))
{
result = RandomDegree.NextInt(SecRnd, 1 << m_degree);
count++;
}
if (count == controltime)
{
result = 1;
}
return(result);
}
/// <summary>
/// Create an irreducible polynomial with the given degree over the field <c>GF(2^m)</c>
/// </summary>
///
/// <param name="Degree">The polynomial degree</param>
/// <param name="SecRnd">The source of randomness</param>
///
/// <returns>he generated irreducible polynomial</returns>
private int[] CreateRandomIrreduciblePolynomial(int Degree, IRandom SecRnd)
{
int[] resCoeff = new int[Degree + 1];
int[] resTemp = new int[Degree + 1];
resCoeff[Degree] = 1;
resCoeff[0] = _field.GetRandomNonZeroElement(SecRnd);
if (ParallelUtils.IsParallel)
{
Parallel.For(0, Degree, i =>
resCoeff[i] = GetRandomElement(SecRnd, _field));
}
else
{
for (int i = 1; i < Degree; i++)
{
resCoeff[i] = GetRandomElement(SecRnd, _field);
}
}
while (!IsIrreducible(resCoeff, _field))
{
int n = RandomDegree.NextInt(SecRnd, Degree);
if (n != 0)
{
resCoeff[n] = GetRandomElement(SecRnd, _field);
}
else
{
resCoeff[0] = _field.GetRandomNonZeroElement(SecRnd);
}
}
return(resCoeff);
}
/// <summary>
/// Create a random field element using PRNG
/// </summary>
///
/// <param name="SecRnd">The IRandom instance</param>
///
/// <returns>A random element</returns>
public int GetRandomElement(IRandom SecRnd)
{
return(RandomDegree.NextInt(SecRnd, 1 << m_degree));
}
/// <summary>
/// Get a randome element over degree Gf2
/// </summary>
///
/// <param name="SecRnd">The source of randomness</param>
/// <param name="GFM">The Gf2 field</param>
///
/// <returns>A random element</returns>
private static int GetRandomElement(IRandom SecRnd, GF2mField GFM)
{
return(RandomDegree.NextInt(SecRnd, 1 << GFM.Degree));
}
