I'm working on a true random number generator, and I came across this phrase in the American NIST guide, in section 6.4.1 Non-Approved Conditioning Components:
The entropy rate provided shall be no greater than the entropy rate provided by the input to the conditioning component; full entropy shall not be provided by non-approved conditioning components.
This suggests that you can have a random number generator that does not provide full entropy. So if you use the de-rigour noisy diode source natively generating approximately 50% pure entropy, your generator can only output 50% entropy. I'm unaware of any source that can natively generate 8 bits /byte entropy. It would actually be undesirable to run the source sampling equipment cranked up to 100% for many engineering reasons.
What is the point of a true random number generator that only produces half pure entropy? Do you only use it half of the time? Or do you just use every other byte (the random ones), ignoring the predictable ones? Seriously though, is it just a thinly veiled warning that "it's our way or no way"? Or..?