# Making PRFs out of PRGs

Is it possible that we take a $PRG$ $G(k)$ of stretch $n\cdot2^n$, and read its output as the table of a $PRF$ $F(K)$ with input and output size of $n$?

Intuitively it sounds possible however I read it somewhere that this may not be done.

• Do you mean $\: n\cdot 2^{\hspace{.02 in}n} \;$? $\;\;\;$ (Instead of $\: n.2^n \;$.) $\;\;\;\;\;\;\;\;$ – user991 Mar 18 '15 at 3:51
• Yes. Sorry for the typo – user1 Mar 18 '15 at 12:06
• Still no comments :) ? – user1 Apr 7 '15 at 17:34