//Checks to see if two polynoms are equal by comparing their values
public override bool Equals(object ob)
{
IrreduciblePolynom poly = ob as IrreduciblePolynom;
if (poly == null)
{
return(base.Equals(ob));
}
return(PolynomValue.Equals(poly.PolynomValue));
}
//Generates enumerable for random finite field polynoms using a given Irreducible polynom and size
private static IEnumerable <FFPolynom> GenerateRandomPolynom(IrreduciblePolynom irreduciblePolynomial, int total)
{
RandomNumberGenerator rng = RandomNumberGenerator.Create();
for (int i = 0; i < total; i++)
{
//Size in bytes = Degree/8 to accomodate the length of the secret phrase
byte[] randomCoeffs = new byte[irreduciblePolynomial.SizeInBytes];
rng.GetBytes(randomCoeffs);
yield return(new FFPolynom(irreduciblePolynomial, randomCoeffs.FromLittleEndUnsignedBytesToBigInt()));
}
}
//Checks for matching with Regex and proccess the , and returns FiniteFieldPoint if success; otherwise null.
internal static bool TryParse(Match matchedShare, out FFPoint res)
{
if (!matchedShare.Success)
{
res = null;
return(false);
}
try
{
//Parse the share string: x - number by order, y - the string after '.' sign
//Gets the string matched by the particular expression. Change to lowcase and apply casing invariant
string xStr = matchedShare.Groups["x"].Value.ToLowerInvariant();
string yStr = matchedShare.Groups["y"].Value.ToLowerInvariant();
//Remove initial 0s to compare with ordinal = 4
while (xStr.StartsWith("0", StringComparison.Ordinal))
{
xStr = xStr.Substring(1);
}
// 1hexChar = 4 bits, so degree in bits = degree * 4
int polynomialDegree = yStr.Length * 4;
IrreduciblePolynom irp = new IrreduciblePolynom(polynomialDegree);
FFPolynom x = new FFPolynom(irp, BigInteger.Parse(xStr));
// Create an array of bites (big endian) with the length in bytes as initial phrase, initialize to 0
byte[] yArr = new byte[yStr.Length / 2];
for (int i = 0; i < yStr.Length; i += 2)
{
//Convert a hex-string to byte representation (1hex = 4 bits).. that's why i/2
yArr[i / 2] = Byte.Parse(yStr.Substring(i, 2), NumberStyles.HexNumber);
}
//Convert yArr to BigInteger and create a finite field polynom
FFPolynom y = new FFPolynom(irp, yArr.FromBigEndUnsignedBytesToBigInt());
res = new FFPoint(x, y);
return(true);
}
catch (Exception e)
{
res = null;
return(false);
}
}
//Shares the secret respectfully to number of shares and threshold
protected virtual SharedSecret ShareImpl(byte[] secret, int threshold, int numberOfShares)
{
//Define irred polynom for a secret
IrreduciblePolynom irreduciblePolynom = IrreduciblePolynom.GiveFromBytes(secret.Length);
BigInteger rawSecret = secret.FromBigEndUnsignedBytesToBigInt();
FFPolynom secretCoeff = new FFPolynom(irreduciblePolynom, rawSecret);
//Generate random polynom with corresponding irred. polynom and given threshold
IEnumerable <FFPolynom> randPolynom = GenerateRandomPolynom(irreduciblePolynom, threshold - 1);
//Construct an array of all coefficients represented as finite field polynoms
FFPolynom[] consTerm = new[] { secretCoeff };
//Concatenate previously created random coefficients converting them as an array
FFPolynom[] allCoefficients = consTerm.Concat(randPolynom).ToArray();
return(new SharedSecret(threshold, irreduciblePolynom, allCoefficients));
}
// internal FFPolynom[] AllCoefficients { get { return _allCoefficients; } }
public SharedSecret(int threshold, IrreduciblePolynom irreduciblePolynomial, FFPolynom[] allCoefficients)
{
Threshold = threshold;
_irreduciblePolynom = irreduciblePolynomial;
_allCoefficients = allCoefficients;
}
//Constructor to create FiniteFieldPolynom object passing the irreducible polynom and its polyn value
public FFPolynom(IrreduciblePolynom primePoly, BigInteger poly)
{
_polynomCoefficients = poly;
PrimePolynom = primePoly;
}
