Re: I-D Action: draft-ietf-6man-default-iids-11.txt

[Brian E Carpenter <[e-mail]>]

On 18/05/2016 14:19, Fernando Gont wrote:
> On 05/16/2016 04:08 PM, Brian E Carpenter wrote:
>> Hi Gengyu,
>>
>>>> RID is not random or random identifier according to the context above.
>>>>
>>>> F() is an inreverse function, not a pseudorandom function.
>>
>> I agree that this is incorrect use of terminology; an irreversible hash is
>> not mathematically equivalent to a pseudo-random number generator. But the
>> effect is the same: an attacker has no way to predict the next F(x) or to
>> obtain the value of x. As far as practical engineering goes, F() can be treated
>> as a random number. So I don't see why this invalidates the use of RFC 7217.
>>
>> You could submit an erratum for RFC 7217 at http://www.rfc-editor.org/errata.php#reportnew
>> so that the terminology can be corrected when the document is updated.
> 
> FWIW, the term "PRF" (as *opposed*) to PRNG was suggested by Alfred
> Hoenes -- IIRC, a mathematician. IIRC, he noted that a hash function is
> simply one possible way of a PRF.

Well, it's complicated (https://en.wikipedia.org/wiki/Pseudorandom_function_family).
As engineers, I think we do better to focus on what matters to us: we need
an unpredictable and unguessable bit string, which we carelessly call 'random'.

   Brian