public void When_GenerateParameters_Should_ReturnCorrectValues()
{
for (int i = 0; i < 3; i++)
{
DsaSystemParameters parameters = _generator.GenerateParameters(1024, 160, 160);
_primalityTester.CheckPrimality(parameters.Q).Should().BeTrue();
_primalityTester.CheckPrimality(parameters.P).Should().BeTrue();
//p - 1 is a multiple of q
((parameters.P - 1) % parameters.Q).Should().BeEquivalentTo(BigInteger.Zero);
//g^q is congruent to mod 1
BigInteger.ModPow(parameters.G, parameters.Q, parameters.P).Should().BeEquivalentTo(BigInteger.One);
}
}
public DsaSystemParameters GenerateParameters(int L, int N, int seedLen)
{
#region CONDITIONS
//SHA-1 used
//Bit length of the output block of choosen hash function, shall be equal to or greater than N
int outlen = 160;
// check combination support
if (!CheckLengthCombinations(L, N))
{
throw new ArgumentException($"Combination of lengths: L={L} and N={N} is not supported");
}
if (outlen < N)
{
throw new ArgumentException("Outlen cannot be less than N");
}
// insisted by FIPS standard
if (seedLen < N)
{
throw new ArgumentException("Seedlen cannot be less then N");
}
#endregion
// calculate equation parameters L - 1 = n * 160(outlen) + b
int n = (int)Math.Ceiling((double)L / outlen) - 1;
int b = L - 1 - (n * outlen);
// create container for seed
int remainingBits = seedLen % 8;
byte[] seed = new byte[(seedLen / 8) + (remainingBits == 0 ? 0 : 1)];
BigInteger outlenPow = BigInteger.Pow(2, seedLen);
BigInteger p, q;
bool outerLoop = true;
do
{
q = GenerateQ(outlenPow, remainingBits, seed);
bool innerLoop = true;
int counter = 0, offset = 2;
do
{
p = GenerateP(L, outlen, outlenPow, n, b, seed, q, ref offset);
if (p < BigInteger.Pow(2, L - 1))
{
UpdateControlVariables(n, ref outerLoop, ref innerLoop, ref counter, ref offset);
}
else
{
if (_primalityTester.CheckPrimality(p))
{
outerLoop = false;
innerLoop = false;
}
else
{
UpdateControlVariables(n, ref outerLoop, ref innerLoop, ref counter, ref offset);
}
}
} while (innerLoop);
} while (outerLoop || (p - 1) % q != 0);
BigInteger g = GenerateG(p, q);
return(new DsaSystemParameters(p, q, g));
}