[Gen-art] Re: Gen-ART review of draft-ietf-ltans-ers-13.txt

Triggered by seeing -14 come out:

On 2007-05-21 20:44, Carl Wallace wrote:
>>> 1. At the end of section 4.2:
>>>
>>>  The data (e.g. certificates, CRLs or OCSP-Responses) 
>> needed to verify  
>>> the timestamp SHOULD be stored in the timestamp itself or MUST be  
>>> preserved otherwise.
>>>
>>> I find this insufficiently clear. When would it be 
>> acceptable not to 
>>> store these data in the timestamp, and if not done so, how 
>> would the 
>>> retriever know where to look?
>> [tg]: There are three main reasons why we did intentionally 
>> write this up in this level of detail: 
>> At first, most of the verification of a RFC3161-timestamp has 
>> been documented very well in the timestamp and CMS 
>> specifications. Second, ERS is open for other timestamps as 
>> well (e.g. ISO-18014-x) and they may (and do) require other 
>> verification data than RFC3161, plus these other formats may 
>> not be able to store all the necessary information for 
>> verification inside their data structures. 
>> And third, as some of the verification data may be dependent 
>> on the use case and country where it is verified, the WG 
>> works on the I-D 
>> http://www.ietf.org/internet-drafts/draft-ietf-ltans-validate-
>> 01.txt to describe the verification and the required data in 
>> more detail. 
> 
> In addition to the above, the "SHOULD be stored in the timestamp"
> recommendation is present in the spec because this is the easiest option.
> If the timestamp contains all of the verification data, then there is less
> work for the verifier to perform.  However, this also freezes the
> verification context (if this is the only means of preserving verification
> data).  There is a companion specification that defines how to use SCVP and
> ERS to preserve certificates and CRLs independent of a data item that is
> archived.  This has a few benefits, including decreasing the storage burden
> on the archive and avoiding freezing the validation context.  
> 

I'm still a little unhappy about the SHOULD. How does an implementor know
that it's OK to ignore the SHOULD? If the data is not stored in the timestamp,
shouldn't you say that a pointer to the data MUST be stored in the timestamp?

     Brian

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