public static SplitSecret Split(SecretShareType shareType, byte[] secret, int threshold, Diffuser diffuser)
{
var irreduciblePolynomial = IrreduciblePolynomial.CreateOfByteSize(secret.Length);
var rawSecret = secret.ToBigIntegerFromBigEndianUnsignedBytes();
var diffusedSecret = diffuser.Scramble(rawSecret, secret.Length);
var secretCoefficient = new FiniteFieldPolynomial(irreduciblePolynomial, diffusedSecret);
var allCoefficients = new[] { secretCoefficient }
.Concat(
GetRandomPolynomials(
irreduciblePolynomial,
threshold - 1)
)
.ToArray();
var passPhrase = new SecureString();
try {
foreach (var currentChar in secret.ToHexString()) {
passPhrase.AppendChar(currentChar);
}
}
catch {
passPhrase = null;
}
if((passPhrase == null) || (passPhrase.Length == 0)) {
passPhrase = null;
}
return new SplitSecret(shareType, threshold, irreduciblePolynomial, allCoefficients, passPhrase);
}
private static FiniteFieldPoint AdjustPoint(int totalPoints, FiniteFieldPoint point) {
var correction = new FiniteFieldPolynomial(point.Y.PrimePolynomial, BigInteger.One);
var correctionMultiplier = point.X;
for (int i = 1; i <= totalPoints; i++) {
correction = correction*correctionMultiplier;
}
var newY = point.Y + correction;
return new FiniteFieldPoint(point.X, newY);
}
public void TestInverse() {
var rijndaelPoly = new IrreduciblePolynomial(8);
var a = new FiniteFieldPolynomial(rijndaelPoly, 6, 4, 1, 0);
var expectedInverse = new FiniteFieldPolynomial(rijndaelPoly, 7, 6, 3, 1);
var actualInverse = a.GetInverse();
Assert.AreEqual(expectedInverse.ToString(), actualInverse.ToString());
var productSanityCheck = a*actualInverse;
Assert.IsTrue(productSanityCheck.One.Equals(productSanityCheck));
}
private static FiniteFieldPoint AdjustPoint(int totalPoints, FiniteFieldPoint point)
{
var correction = new FiniteFieldPolynomial(point.Y.PrimePolynomial, BigInteger.One);
var correctionMultiplier = point.X;
for (int i = 1; i <= totalPoints; i++)
{
correction = correction * correctionMultiplier;
}
var newY = point.Y + correction;
return(new FiniteFieldPoint(point.X, newY));
}
public static FiniteFieldPolynomial EvaluateAt(long x, FiniteFieldPolynomial[] coefficients) {
// Use Horner's Scheme: http://en.wikipedia.org/wiki/Horner_scheme
FiniteFieldPolynomial xAsPoly = coefficients[0].GetValueInField(x);
// assume the coefficient for highest monomial is 1
FiniteFieldPolynomial result = xAsPoly.Clone();
for (int i = coefficients.Length - 1; i > 0; i--) {
result = result + coefficients[i];
result = result*xAsPoly;
}
result = result + coefficients[0];
return result;
}
public static FiniteFieldPolynomial EvaluateAt(long x, FiniteFieldPolynomial[] coefficients)
{
// Use Horner's Scheme: http://en.wikipedia.org/wiki/Horner_scheme
FiniteFieldPolynomial xAsPoly = coefficients[0].GetValueInField(x);
// assume the coefficient for highest monomial is 1
FiniteFieldPolynomial result = xAsPoly.Clone();
for (int i = coefficients.Length - 1; i > 0; i--)
{
result = result + coefficients[i];
result = result * xAsPoly;
}
result = result + coefficients[0];
return(result);
}
internal static bool TryParse(Match match, out FiniteFieldPoint result)
{
if (!match.Success)
{
result = null;
return(false);
}
try {
var xString = match.Groups["x"].Value.ToLowerInvariant();
var yString = match.Groups["y"].Value.ToLowerInvariant();
// get rid of any initial 0's
while (xString.StartsWith("0", StringComparison.Ordinal))
{
xString = xString.Substring(1);
}
// Each hex letter makes up 4 bits, so to get the degree in bits
// we multiply by 4
int polynomialDegree = yString.Length * 4;
var irp = new IrreduciblePolynomial(polynomialDegree);
var x = new FiniteFieldPolynomial(irp, BigInteger.Parse(xString));
// get bytes
var bigEndianBytes = new byte[yString.Length / 2];
for (int i = 0; i < yString.Length; i += 2)
{
bigEndianBytes[i / 2] = Byte.Parse(yString.Substring(i, 2), NumberStyles.HexNumber);
}
var y = new FiniteFieldPolynomial(irp, bigEndianBytes.ToBigIntegerFromBigEndianUnsignedBytes());
result = new FiniteFieldPoint(x, y);
return(true);
}
catch (Exception exception) {
result = null;
return(false);
}
}
public void BasicTests() {
var rijndaelPoly = new IrreduciblePolynomial(8);
var a = new FiniteFieldPolynomial(rijndaelPoly, 6, 4, 1, 0);
var b = new FiniteFieldPolynomial(rijndaelPoly, 7, 6, 3, 1);
var product = a*b;
// "a" and "b" are inverses, so their product is 1
Assert.AreEqual(1, (int)product.PolynomialValue);
var g = new FiniteFieldPolynomial(rijndaelPoly, BigInteger.Parse("0e5", NumberStyles.HexNumber));
var p = new FiniteFieldPolynomial(rijndaelPoly, BigInteger.One);
// g is a generator, so we should generate all values except 0
var vals = new HashSet<BigInteger> {p.PolynomialValue};
for (int i = 0; i < 255; i++) {
p = p*g;
vals.Add(p.PolynomialValue);
}
Assert.AreEqual(255, vals.Count);
Assert.IsTrue(vals.Contains((p*g).PolynomialValue));
}
public SecretShare GetShare(int n)
{
var xPoly = new FiniteFieldPolynomial(_IrreduciblePolynomial, new BigInteger(n));
var y = FiniteFieldPolynomial.EvaluateAt(n, _AllCoefficients);
return new SecretShare(_ShareType, new FiniteFieldPoint(xPoly, y));
}
public SplitSecret(SecretShareType shareType, int threshold, IrreduciblePolynomial irreduciblePolynomial, FiniteFieldPolynomial[] allCoefficients, SecureString passPhrase = null)
{
_ShareType = shareType;
Threshold = threshold;
_IrreduciblePolynomial = irreduciblePolynomial;
_AllCoefficients = allCoefficients;
_PassPhrase = passPhrase;
}
internal static bool TryParse(Match match, out FiniteFieldPoint result) {
if (!match.Success) {
result = null;
return false;
}
try {
var xString = match.Groups["x"].Value.ToLowerInvariant();
var yString = match.Groups["y"].Value.ToLowerInvariant();
// get rid of any initial 0's
while (xString.StartsWith("0", StringComparison.Ordinal)) {
xString = xString.Substring(1);
}
// Each hex letter makes up 4 bits, so to get the degree in bits
// we multiply by 4
int polynomialDegree = yString.Length*4;
var irp = new IrreduciblePolynomial(polynomialDegree);
var x = new FiniteFieldPolynomial(irp, BigInteger.Parse(xString));
// get bytes
var bigEndianBytes = new byte[yString.Length/2];
for (int i = 0; i < yString.Length; i += 2) {
bigEndianBytes[i/2] = Byte.Parse(yString.Substring(i, 2), NumberStyles.HexNumber);
}
var y = new FiniteFieldPolynomial(irp, bigEndianBytes.ToBigIntegerFromBigEndianUnsignedBytes());
result = new FiniteFieldPoint(x, y);
return true;
}
catch(Exception exception) {
result = null;
return false;
}
}
public FiniteFieldPoint(FiniteFieldPolynomial x, FiniteFieldPolynomial y) {
X = x;
Y = y;
}
public FiniteFieldPoint(FiniteFieldPolynomial x, FiniteFieldPolynomial y)
{
X = x;
Y = y;
}
