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using System;
using System.Text;
using NUnit.Framework;
using Org.BouncyCastle.Crypto.Prng;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Security.Tests
{
[TestFixture]
public class SecureRandomTest
{
#if !(NETCF_1_0 || PORTABLE)
[Test]
public void TestCryptoApi()
{
SecureRandom random = new SecureRandom(
new CryptoApiRandomGenerator());
CheckSecureRandom(random);
}
#endif
[Test]
public void TestDefault()
{
SecureRandom random = new SecureRandom();
CheckSecureRandom(random);
}
[Test]
public void TestSha1Prng()
{
SecureRandom random = SecureRandom.GetInstance("SHA1PRNG");
CheckSecureRandom(random);
}
[Test]
public void TestSha1PrngBackward()
{
byte[] seed = Encoding.ASCII.GetBytes("backward compatible");
SecureRandom sx = new SecureRandom(seed);
SecureRandom sy = SecureRandom.GetInstance("SHA1PRNG", false); sy.SetSeed(seed);
byte[] bx = new byte[128]; sx.NextBytes(bx);
byte[] by = new byte[128]; sy.NextBytes(by);
Assert.IsTrue(Arrays.AreEqual(bx, by));
}
[Test]
public void TestSha256Prng()
{
SecureRandom random = SecureRandom.GetInstance("SHA256PRNG");
CheckSecureRandom(random);
}
[Test]
public void TestThreadedSeed()
{
SecureRandom random = SecureRandom.GetInstance("SHA1PRNG", false);
random.SetSeed(new ThreadedSeedGenerator().GenerateSeed(20, false));
CheckSecureRandom(random);
}
[Test]
public void TestVmpcPrng()
{
SecureRandom random = new SecureRandom(new VmpcRandomGenerator());
random.SetSeed(SecureRandom.GetSeed(32));
CheckSecureRandom(random);
}
private static void CheckSecureRandom(SecureRandom random)
{
// Note: This will periodically (< 1e-6 probability) give a false alarm.
// That's randomness for you!
Assert.IsTrue(RunChiSquaredTests(random), "Chi2 test detected possible non-randomness");
}
private static bool RunChiSquaredTests(SecureRandom random)
{
int passes = 0;
for (int tries = 0; tries < 100; ++tries)
{
double chi2 = MeasureChiSquared(random, 1000);
// 255 degrees of freedom in test => Q ~ 10.0% for 285
if (chi2 < 285.0)
{
++passes;
}
}
return passes > 75;
}
private static double MeasureChiSquared(SecureRandom random, int rounds)
{
byte[] opts = SecureRandom.GetSeed(2);
int[] counts = new int[256];
byte[] bs = new byte[256];
for (int i = 0; i < rounds; ++i)
{
random.NextBytes(bs);
for (int b = 0; b < 256; ++b)
{
++counts[bs[b]];
}
}
byte mask = opts[0];
for (int i = 0; i < rounds; ++i)
{
random.NextBytes(bs);
for (int b = 0; b < 256; ++b)
{
++counts[bs[b] ^ mask];
}
++mask;
}
byte shift = opts[1];
for (int i = 0; i < rounds; ++i)
{
random.NextBytes(bs);
for (int b = 0; b < 256; ++b)
{
++counts[(byte)(bs[b] + shift)];
}
++shift;
}
int total = 3 * rounds;
double chi2 = 0;
for (int k = 0; k < counts.Length; ++k)
{
double diff = ((double) counts[k]) - total;
double diff2 = diff * diff;
chi2 += diff2;
}
chi2 /= total;
return chi2;
}
}
}
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