public static List <int> CreateSeeds(int number = 16)
{
var rng = new Random(0);
byte[] mainSeed = new byte[4];
rng.NextBytes(mainSeed);
List <byte[]> flips = EncryptionTesting.CreateFlips(mainSeed, number - 1);
flips.Insert(0, mainSeed);
return(flips
.Select(f => f.ToInt32())
.ToList());
}
/// <summary>
/// Tests the Rng distribution 0 being a perfect score.
/// The worst score is 1024* (256 - 10)
/// </summary>
/// <typeparam name="T">Rng type to test</typeparam>
/// <returns></returns>
public static double DistributionTest <T>() where T : IRng
{
// we get 1024 bytes, the expected frequency is 1/256
// or 4 occurrances per byte.
// Worst case, all ocurrances are the same byte
// (no proof for that, but it works for 2 variables:
// d(chi) = 2(f0 - e0)/e0 + 2(f1 - e1)/e1 = 0
// f0 + f1 = e0 + e1 = 1, so f0 + f1 = 1 are all zeroes)
// In that worst case and uniform distribution, we have
// N(one case that happens all the time) + N(rest of the cases that never happen)
// N*[(1 - 1/n)^2/ (1/n) + (n - 1) (0-1/n)^2/(1/n)]
//=N*n [(1 - 1/n)^2 + (n - 1)/n^2]
//=N*n[1 - 1/n] = N(n-1)
//This is verified with the NullRng
const int POP_SIZE = 1024;
//double theoMax = POP_SIZE * (256 - 1);
//random seeds from [0,65535]
int[] seeds = { 0, 7501, 21584, 42875 };
double[] seedResult = new double[seeds.Length];
for (int j = 0; j < seeds.Length; ++j)
{
IRng rng = (IRng)Activator.CreateInstance(typeof(T), seeds[j]);
float[] results = new float[16];
byte[] bytes = new byte[POP_SIZE];
for (int i = 0; i < 16; ++i)
{
rng.NextBytes(bytes);
results[i] = (float)Stats.GTest(EncryptionTesting.GetBlockCount(bytes));
}
seedResult[j] = results.Average();
}
double finalAverage = seedResult.Average();
//if finalAverage = theoMax, we return 0
// if finalAverage = 0, we return 1 (uniform distribution)
//double percentResult = (theoMax - finalAverage) / theoMax;
return(finalAverage);
}
/// <summary>
/// Tests the Rng confusion from 0 to 1.
/// If the seed is changed by one bit, how much does the output change.
/// Exactly 50%, gives a score of 1.
/// 0% or 100% (!input) gives a score of 0
/// </summary>
public static float ConfusionTest <T>() where T : IRng
{
List <int> flipSeeds = CreateSeeds();
List <IRng> rngs = flipSeeds
.Select(s => (IRng)Activator.CreateInstance(typeof(T), s))
.ToList();
var flipBytes = new List <byte[]>(16);
foreach (IRng rng in rngs)
{
byte[] bytes = new byte[1024];
rng.NextBytes(bytes);
flipBytes.Add(bytes);
}
List <float> results = flipBytes
.Select(b => EncryptionTesting.PercentFlips(flipBytes[0], b))
.Skip(1)
.ToList();
float ave = results.Average();
return((0.5f - Math.Abs(0.5f - ave)) / 0.5f);
}
