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

[Sean Turner <[e-mail]>]

> 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)

spt