Re: I-D ACTION:draft-ietf-pkix-time-stamp-08.txt

[thayes@xxxxxxxxxxxx (Terry Hayes)]

Paul Halliden wrote:

> Certainly, as Terry argues, collisions in the TSA's own process will always
> be a concern. Whether or not end entity collisions are a concern to the TSA
> is application dependent.  As a minimum, collisions deliberately created by
> the end entity would be an embarrassment to the TSA and affect the
> perception of it in a public dispute.  Again, I would argue that it is
> safest not to make assumptions about the application.

Embarrassment to the TSA should result from failure to provide a correct and
secure timestamp, not from the content that is being stamped.  If you are
worried about embarrassment, perhaps you should insist on seeing the entire
message, rather than just an imprint.  After all, the imprint may be referring
to racist material, or plans for terrorist attacks.

While I'll grant that the imprint algorithm used (and the appropriateness of the
value given for that algorithm) are important for the functioning of the
process, I don't see any need to have the TSA enforce restrictions on them at
the time the timestamp is created.  If the primary goal is achieved (correct and
secure timestamping of the imprint), then a dispute resolution process can
determine whether a reasonable imprint algorithm (for the time) was used.

A TSA MAY choose enforce restrictions on the imprint, but the standard should
not REQUIRE it.

Terry Hayes