/// <summary>
/// Deterministically generates a blinding polynomial from a seed and a message representative
/// </summary>
///
/// <param name="Seed">The seed value</param>
///
/// <returns>A blinding polynomial</returns>
private IPolynomial GenerateBlindingPoly(byte[] Seed)
{
int N = _encParams.N;
IndexGenerator ig = new IndexGenerator(Seed, _encParams);
if (_encParams.PolyType == TernaryPolynomialType.PRODUCT) //.8, .6
{
SparseTernaryPolynomial r1 = SparseTernaryPolynomial.GenerateBlindingPoly(ig, N, _encParams.DR1);
SparseTernaryPolynomial r2 = SparseTernaryPolynomial.GenerateBlindingPoly(ig, N, _encParams.DR2);
SparseTernaryPolynomial r3 = SparseTernaryPolynomial.GenerateBlindingPoly(ig, N, _encParams.DR3);
return new ProductFormPolynomial(r1, r2, r3);
}
else
{
if (_encParams.Sparse)
return SparseTernaryPolynomial.GenerateBlindingPoly(ig, N, _encParams.DR);
else
return DenseTernaryPolynomial.GenerateBlindingPoly(ig, N, _encParams.DR);
}
}
/// <summary>
/// Generates a blinding polynomial using an IndexGenerator
/// </summary>
///
/// <param name="Ig">An Index Generator</param>
/// <param name="N">The number of coefficients</param>
/// <param name="Dr">The number of ones / negative ones</param>
///
/// <returns>A blinding polynomial</returns>
public static DenseTernaryPolynomial GenerateBlindingPoly(IndexGenerator Ig, int N, int Dr)
{
return new DenseTernaryPolynomial(GenerateBlindingCoeffs(Ig, N, Dr));
}
/// <summary>
/// Generates a blinding polynomial using an IndexGenerator
/// </summary>
///
/// <param name="Ig">An Index Generator</param>
/// <param name="N">The number of coefficients</param>
/// <param name="Dr">The number of ones / negative ones</param>
///
/// <returns>A blinding polynomial</returns>
public static SparseTernaryPolynomial GenerateBlindingPoly(IndexGenerator Ig, int N, int Dr)
{
int[] coeffs = new int[N]; // an IntegerPolynomial-style representation of the new polynomial
int[] ones = new int[Dr];
int i = 0;
while (i < Dr)
{
int r = Ig.NextIndex();
if (coeffs[r] == 0)
{
ones[i] = r;
coeffs[r] = 1;
i++;
}
}
int[] negOnes = new int[Dr];
i = 0;
while (i < Dr)
{
int r = Ig.NextIndex();
if (coeffs[r] == 0)
{
negOnes[i] = r;
coeffs[r] = -1;
i++;
}
}
return new SparseTernaryPolynomial(N, ones, negOnes);
}
/// <summary>
/// Generates an <c>int</c> array containing <c>dr</c> elements equal to <c>1</c>
/// and <c>dr</c> elements equal to <c>-1</c> using an index generator.
/// </summary>
///
/// <param name="Ig">An Index Generator</param>
/// <param name="N">The number of coefficients</param>
/// <param name="Dr">The number of ones / negative ones</param>
///
/// <returns>An array containing numbers between <c>-1</c> and <c>1</c></returns>
private static int[] GenerateBlindingCoeffs(IndexGenerator Ig, int N, int Dr)
{
int[] r = new int[N];
for (int coeff = -1; coeff <= 1; coeff += 2)
{
int t = 0;
while (t < Dr)
{
int i = Ig.NextIndex();
if (r[i] == 0)
{
r[i] = coeff;
t++;
}
}
}
return r;
}
