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Re: Comment regarding Nonce size
> PS: the above paragraph about the pre-hashing of long keys in
> HMAC also
> gives you a partial answer on your other question
> about what's the benefit of using nonces that are longer than the hash
> output size: while the extra length is not strictly needed, and can
> even be considered a "waste" if the nonce bits are TRULY random,
> the extra length may potentially help in the typical case
> that these bits
> are generated out of a weaker source of (pseudo) randomness.
It seems to me that this is only an advantage if you have a weak RNG but you
don't know it. If you think you have a weak RNG, wouldn't a better solution
be to generate a large nonce with sufficient entropy and then hash it down
to the size of the HMAC output? That would save bits on the wire, with no
apparent drawbacks.
Andrew
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