Thank you for the contribution and for thinking about the issue as a fundamental one that has to be proven correct rather than hacking on it until it seems to w

Thank you for the contribution and for thinking about the issue as a fundamental one that has to be proven correct rather than hacking on it until it seems to work. The use of RDRAND was especially overzealous. The problem is always finding the line between retaining entropy and performance - in this case (without having done the statistics) I believe you have done the right thing. If I wanted to contribute an entropy mixer not based on CRC32 (as the current one is) that is much faster, includes test vectors and entropy analysis - where would be a good place to start?