By the way, your version of mutagen (which you updated not so long ago) has become faster to check, before 300 billion took 12 hours, and now 8 hours. Cut another 6 hours and it will be like in Cyclone

for (int pos : flips) {
Int mask;
mask.SetInt32(1);
mask.ShiftL(pos);
currentKey.Xor(&mask);
}
Yes, this is the maximum. Only if you program XOR to work in assembly might it be faster. The same applies to the combination generator - they are a bottleneck
