I've read a lot of information about PRNGs, PRFs and KDFs. As far as I know:

PRNG: The seed for the PRNG must be a uniform string. It transforms a short real uniform string into some bits of pseudo-randomness.

PRF: The PRF gets a uniform key and some additional input and transforms it into a string of pseudo-randomness.

KDF: For example the HKDF scheme uses the hmac as PRF and does not need any uniform input string. It generates some pseudo-randomness.

So far, is that right? I would like to get some additional information about literature on that topcs, in particular further on the inputs of PRF and KDF.

  • $\begingroup$ The reference on KDFs and their security models and guarantees is probably the introductionary paper for HKDF. $\endgroup$
    – SEJPM
    Jul 5 '18 at 8:59
  • $\begingroup$ Hi, yes I already know hat paper. May be I did not understand the fully impact and consequences of that paper. But the most important question to me is: Is it right, that the KDF (f.e. the HKDF-Scheme) does not need any uniform input string? although it would be better, as far as I understood it, if it were? $\endgroup$
    – chris000r
    Jul 8 '18 at 15:22

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