Re: [Mobopts] Re: Comments on draft-kempf-mobopts-ringsig-ndproxy-02.txt

James Kempf wrote:

>> This is what RFC 3972 says:
>>
>>   Note that the hash values are computed
>>   over the entire CGA Parameters data structure, including any
>>   unrecognized extension fields.
>>
>> Now, the field itself is underspecified although its usage in the
>> address calculation is clear (above). What we would probably need
>> to do is to specify first a TLV structure for the extensions, and
>> then one extension for the purposes of MCGA. But I don't
>> think we need to touch the calculation rules.
>>
>
> The draft has a specification for a generic TLV structure. I suppose 
> it does no harm in including the TLV values into the calculation, but 
> it is not the way most protocols I'm familiar with handle this. 
> Typically, the semantically relevant fields are extracted and used, 
> the identifying fields are discarded. But it does simplify the 
> implementation, less parsing.

Your draft has the generic TLV thing, but RFC 3972 did not have that.
The generic TLV structure is necessary, but I see that as an add-on
to RFC 3972 rather than something that needs to change other pieces
when its specified. Your draft does this very well, as long as we
don't change the address calculation rules.

I do prefer including everything as an opaque bit string in the
calculation. First of all, this is what RFC 3972 says. Secondly,
It ensures that there are no replacement attacks where
you keep the actual value but replace its type. Thirdly, its
simpler.

--Jari

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