Re: [stir] Eric Rescorla's Discuss on draft-ietf-stir-certificates-16: (with DISCUSS)

[Eric Rescorla <[e-mail]>]

On Wed, Dec 13, 2017 at 8:36 AM, Sean Turner <[e-mail]> wrote:

>
>
> > On Dec 13, 2017, at 11:24, Adam Roach <[e-mail]> wrote:
> >
> > On 12/12/17 17:58, Eric Rescorla wrote:
> >>
> >>    national policies.  The count field is only applicable to start
> >>    fields' whose values do not include "*" or "#" (i.e., a
> >>    TelephoneNumber that does not include "*" or "#").  count never
> >>    overflows a TelephoneNumber digit boundary (i.e., a
> >>    TelephoneNumberRange with TelephoneNumber=10 with a count=91 will
> >>    address numbers 10-99).
> >>
> >> This text doesn't seem very clear. When you say "never overflows a digit
> >> boundary" do you mean "doesn't extend the integer to the left"? Because
> >> you sure seem to be overflowing the 1s place here.
> >
> > Based on the in-room conversation in Singapore, the notion here seems to
> be that the number does not increase in length.
>
> Yep.
>
> >> Is the algorithm that you are given the input TN, Count, and TN
> >> consists D digits that the range is:
> >>
> >>   MIN(TN + Count, 10^D - 1)
> >>
> >> That would be consistent with your example here, but I don't think
> consistent
> >> with your text. Or do you mean something else?
> >>
> >
> > Your formula above matches my understanding, and I think including it in
> the document as the formal definition of how 'count' behaves would be the
> best way to address the lack of clarity you cite.
>
> Agreed.  How about this change:
>
> OLD:
>
>     count never overflows a TelephoneNumber digit
>     boundary (i.e., a TelephoneNumberRange with
>     TelephoneNumber=10 with a count=91 will address
>     numbers 10-99).
>
> NEW:
>
>     count never makes the number increase in length
>     (i.e., a TelephoneNumberRange with TelephoneNumber=10
>     with a count=91 will address numbers 10-99); formally,
>     given the inputs count and TelephoneNumber of length D
>     the end of the TelephoneNumberRange is:
>     MIN(TelephoneNumber + count, 10^D - 1)
>


This seems fine.

-Ekr