private ulong GetDigestsFromRandomPools(ICollection <byte[]> digests)
{
// Based on Dodis et al sections 5.2 and 6.3.
ulong randomPoolUsedMask = 0;
if (_RandomPools.Length > 0)
{
// Create a bit mask to determine which pools to draw from.
ulong randomPoolNumber = 0;
ulong randomPoolMask = (1UL << (_RandomPools.Length)) - 1;
var anyDigests = digests.Any();
do
{
// Chance of random selection is at best 1/2, and may be less, depending on the value of _RandomFactor.
randomPoolNumber = _Rng.GetRandomUInt64();
for (int i = 0; i < _RandomFactor; i++)
{
randomPoolNumber = randomPoolNumber & _Rng.GetRandomUInt64();
}
// If any random pools are defined, and there isn't already a digest, we must ensure at least one pool is drawn from.
} while (!anyDigests && (randomPoolNumber & randomPoolMask) == 0);
// Read from pools.
for (int i = 0; i < _RandomPools.Length; i++)
{
if (PoolIsUsedRandom(i, randomPoolNumber))
{
digests.Add(_RandomPools[i].GetDigest());
randomPoolUsedMask = randomPoolUsedMask | (1UL << i);
}
}
}
return(randomPoolUsedMask);
}