/// <summary>
/// Evaluates the shared secrets of secret with polynom of degree t and numberOfPlayers players.
/// </summary>
public static ShareDetails DetailedShare(Zp secret,
int numPlayers, int polynomDeg)
{
if (numPlayers <= polynomDeg)
throw new ArgumentException("Polynomial degree cannot be bigger or equal to the number of players");
// Creating the Random Polynomial - f(x)
var randomMatrix = ZpMatrix.GetRandomMatrix(1, polynomDeg + 1, secret.Prime);
// The free variable in the Random Polynomial( f(x) ) is the seceret
randomMatrix.SetMatrixCell(0, 0, secret);
// Create vanderMonde matrix
var vanderMonde = ZpMatrix.GetPrimitiveVandermondeMatrix(polynomDeg + 1, numPlayers, secret.Prime);
// Compute f(i) for the i-th player
var sharesArr = randomMatrix.Times(vanderMonde).ZpVector;
var details = new ShareDetails(randomMatrix.GetMatrixRow(0), sharesArr);
return details;
}
/// <summary>
/// Evaluates the shared secrets of secret with polynom of degree t and numberOfPlayers players.
/// </summary>
public static ShareDetails DetailedShare(Zp secret,
int numPlayers, int polynomDeg)
{
if (numPlayers <= polynomDeg)
{
throw new ArgumentException("Polynomial degree cannot be bigger or equal to the number of players");
}
// Creating the Random Polynomial - f(x)
var randomMatrix = ZpMatrix.GetRandomMatrix(1, polynomDeg + 1, secret.Prime);
// The free variable in the Random Polynomial( f(x) ) is the seceret
randomMatrix.SetMatrixCell(0, 0, secret);
// Create vanderMonde matrix
var vanderMonde = ZpMatrix.GetPrimitiveVandermondeMatrix(polynomDeg + 1, numPlayers, secret.Prime);
// Compute f(i) for the i-th player
var sharesArr = randomMatrix.Times(vanderMonde).ZpVector;
var details = new ShareDetails(randomMatrix.GetMatrixRow(0), sharesArr);
return(details);
}
private IList<Zp> ConstructRxPolynomial(ShareDetails aSharesDetails,
ShareDetails bSharesDetails, ShareDetails abSharesDetails, ShareDetails rSharesDetails)
{
var fax = aSharesDetails.RandomPolynomial;
var fbx = bSharesDetails.RandomPolynomial;
var hx = abSharesDetails.RandomPolynomial;
var rx = rSharesDetails.RandomPolynomial;
var RxPolynomial = new Zp[2 * PolynomialDeg + 1];
/* Initialize RxPolynomial coefs with zeros */
for (int i = 0; i < 2 * PolynomialDeg + 1; i++)
RxPolynomial[i] = new Zp(Prime, 0);
/* First calculate fax*fbx - hx */
for (int i = 0; i < fax.Count; i++)
{
Zp temp = fax[i];
for (int j = 0; j < fax.Count; j++)
RxPolynomial[i + j].Add(temp.ConstMul(fbx[j]));
RxPolynomial[i].Sub(hx[i]);
}
/* Calculate x*rx+fax*fbx - hx*/
for (int i = 0; i < rx.Count; i++)
RxPolynomial[i + 1].Add(rx[i]);
return new List<Zp>(RxPolynomial);
}
