Achieving Randomness
There are two types of answers:


Practical: You are looking for good stream ciphers. Several exist, though we don't know for sure that they are secure.
Theoretical: You are looking for cyptographically secure PRNGs. There are several suspected constructions, but such objects are not known to exist; if P=NP, then they don't exist.


In both cases, there is quite a wide literature on the subject.