/// <summary>
/// I'm not 100% sure that this is the best way to get this hash
/// </summary>
private static BigInteger Hash2(byte[] data)
{
drbg.Reseed(data, hash2String);
var x = drbg.GenerateInteger(GroupParameters.SubgroupSize);
return(mod.Pow(GroupParameters.Generator, x));
}
private static void TestMultiExp()
{
Console.Write("Testing multi-exponentiation");
int k = 111;
var seed = new byte[1000];
var r = new Random();
r.NextBytes(seed);
var rnd = new HMACDRBG(seed);
var mod = new Modular(new BigInteger(5555555566666777777));
var g = Enumerable.Range(0, k).Select(i => rnd.GenerateInteger(BigInteger.One << r.Next(200) + 200)).ToArray();
var me = new MultiExponentiation(mod.Modulus, g);
for (int i = 0; i < 1000; ++i)
{
var e = Enumerable.Range(0, k).Select(j => rnd.GenerateInteger(BigInteger.One << r.Next(100) + 100)).ToArray();
//var z = mod.Pow(g, e, ref cache);
var z = me.Pow(e);
var z2 = BigInteger.One;
for (int j = 0; j < k; ++j)
{
z2 = (z2 * BigInteger.ModPow(g[j], e[j], mod.Modulus)).Mod(mod.Modulus);
}
if (!z.Equals(z2))
{
Console.WriteLine("ouch");
}
if (i % 100 == 0)
{
Console.Write('.');
}
r.NextBytes(seed);
rnd.Reseed(seed);
}
Console.WriteLine();
}
public static RingSignature GenerateSignature(byte[] message, BigInteger[] publicKeys, BigInteger privateKey, int identity)
{
var r = rng.GenerateInteger(GroupParameters.SubgroupSize);
var c = new BigInteger[publicKeys.Length];
var b = BigInteger.Zero;
for (int i = 0; i < publicKeys.Length; ++i)
{
if (i != identity)
{
c[i] = rng.GenerateInteger(GroupParameters.SubgroupSize);
b = (b + c[i]).Mod(GroupParameters.SubgroupSize);
}
}
var x = (BigInteger[])publicKeys.Clone();
x[identity] = GroupParameters.Generator;
c[identity] = r;
var a = mod.Pow(x, c);
var L = ConcatInts(null, publicKeys);
var h = Hash2(L);
var y0 = mod.Pow(h, privateKey);
var prefix = ByteArrayUtils.ConcatBytes(ConcatInts(L, y0), message);
var h1 = Hash1(ConcatInts(prefix, a, mod.Pow(new[] { h, y0 }, new[] { r, b })));
c[identity] = (h1 - b).Mod(GroupParameters.SubgroupSize);
var s = (r - c[identity] * privateKey).Mod(GroupParameters.SubgroupSize);
return(new RingSignature(y0, s, c));
}