alt Hacker NewsUnfortunately you are not correct, and djb explains it quite well here:
https://blog.cr.yp.to/20140205-entropy.html
TL;DR adding a compromised source of entropy to a pool of already secure sources of entropy can catastrophically compromise the final result.
It's better to source entropy from a smaller number of harder-to-compromise sources. That's why I like the iterated hashes method; the security surface area is both very small and highly likely to be well tested.
Indeed, that’s a real attack.
From that page:
>>>what I'm advocating here, for security reasons, is a sharp transition between
* before crypto: the whole system collecting enough entropy;
* after: the system using purely deterministic cryptography, never adding any more entropy.<<<
Which is exactly how a XOF should be used, and how I used the XOF in my code. A malicious source of entropy will need to perform 2^n operations to control n bits of the XOF’s output, and that’s assuming the malicious entropy source somehow perfectly knows the other entropy the XOF is using.