Subject: Comments on RFC3161

From: Alfonso De Gregorio <[email-masked]>
Date: Thu, 13 Sep 2001 14:31:02 +0200

Hi Everyone,

In my opinion, in a future rfc3161 update, the following parts should
be corrected .

Comment A
There is an inconsistency between these statements present in section 1:
 - "It also establishes several security-relevant requirements for TSA
   operation, with regards to processing requests to generate responses"
 - "This standard does not establish overall security requirements for
   TSA operation, just like other PKIX standards do not establish such
   requirements for CA operation"

Comment B
There should be no ambiguity (neither minor) in the scope of TSP. 

In my opinion, it's preferable to say that "The TSA is a TTP that 
creates time-stamp tokens in order to indicate that a datum existed 
_at_ a particular point in time", according to section 2.
And should be avoided to say that "A time-stamping service supports 
assertions of proof that a datum existed _before_ a particular time",
as stated several times in section 1.   
It's part of the verification phase to understand if a token is subsequent 
or antecedent to another one.

Comment C
The part of section 2.4.2:

rfc3161> In such a case, the ordering of time-stamp tokens issued by 
rfc3161> the same TSA or different TSAs is only possible when the 
rfc3161> difference between the genTime of the first time-stamp token 
rfc3161> and the genTime of the second time-stamp token is greater than 
rfc3161> the sum of the accuracies of the genTime for each time-stamp token.

should be replaced with: 
In such a case, the ordering of time-stamp tokens issued by 
the same TSA or different TSAs is only possible when the absolute value
difference between the genTime of the first time-stamp token 
and the genTime of the second time-stamp token is greater than 
the sum of the accuracies of the genTime for each time-stamp token.

In fact, when a TSA clock drift outside the declared accuracy it's
possible to observe time-stamp tokens that have inconsistent genTime
associated with them (eg. the genTime value of a _first_ time-stamp 
token is grater either than the genTime value of a second token, or
the sum of the accuracies of the two tokens); please refer to my 
previous message for an example.

Thanks,
alfonso

---

From: Denis Pinkas <[email-masked]>
Date: Thu, 13 Sep 2001 15:57:55 +0200

Alfonso,
 
> In my opinion, in a future rfc3161 update, the following parts should

Since RFC 3161 has just been issued in August 2001, it will not be re-issued
shortly.

>    requirements for CA operation"

This is not inconsistent: "several security-relevant requirements" is
different from "overall security requirements".

> as stated several times in section 1.

No. This point has been discussed on the pkix mailing list and the current
text reflects the concensus reached. 

> the sum of the accuracies of the genTime for each time-stamp token.

It is implicit that such comparisons are made between TSA servers that are
trusted and compliant with the requirements. So adding the word "absolute"
is not necessary in that context.
 
> In fact, when a TSA clock drift outside the declared accuracy 

Hence the TSA becomes non-conformant.

Denis

> it's