Under the following premise:
I need to generate multiple symmetric keys;
I cannot be sure about the quality of local system RNG;
I already have a strong key K (generated by other means / elsewhere).
Does it make sense to encrypt the output of system RNG with K (or some derivation of it) with the purpose of strengthening generated keys. More generally, can I strengthen the output of the RNG using K?
Length - let's say that the entropy of K is 128 bit. Number of keys - multiple, but not numerous (several or dozens, not more).
More clarifications and comment:
Persistent (and secure, as long as the whole system is not compromised) storage is available, so a sequential IV can be implemented.
I am starting to have doubts about the idea that RNG may be flaky while the system is still not compromised, but initially I assumed that RNG quality is not black and white and because it is easy to provide K, generated keys can be strengthened.
Apropos, I can deliver 256 bits K, so I can really just use it as seed for a PRNG and forget about all else. In any way, a compromise on the source of K is total falldown, so this starts to look like a straightforward option.