Re: Conjectured pseudorandom functions

From: David Wagner (daw_at_taverner.cs.berkeley.edu)
Date: 04/30/05 

Date: Sat, 30 Apr 2005 03:44:08 +0000 (UTC)

>What are the conjectured pseudorandom functions with arbitrary input
>length commonly used in practice?

SHA1-HMAC is a good example. AES-OMAC is another.

>Is it necessary to choose the key of
>a pseudorandom function uniformly from the key space in order to ensure
>its randomness?

For most of these PRFs, yes.

>Could we just feed the output of the pseudorandom
>function on an input x as the key to another pseudorandom function?

Assuming you mean F(F(k,x), y), the answer is basically yes,
depending on what you want to do with it and what you want to
achieve with this construction. Do you want to elaborate?