Re: XAdES TimeStamping implementation

Dear Jerman,

You are right when you say that the current ASN.1 TImeStamp standard
does not recognize an XML structure.
But XAdES specifies mechanisms, not only for including time-stamps
(encapsulated within XML structures), but also for IDENTIFYING WHICH
parts of the signature and of the signed documents where included within
the computation of the hash to be sent to the TSA. This should allow, when
dealing with one of the different time-stamps that appear within XAdES,
identify
what each one is actually time-stamping. It is a matter of the supporting
structure, 
not of the generated time-stamp token itself.  As I said in a former
message, this mechanisms
were largely discussed  in the XAdES plugtest event organized by ETSI, and you
have the URL where you cand find the final report where this issue is 
commented, and the proposal for review is made available.

Concerning to the parts of the documents that were time-stamped, the
mechanisms
rely on the referencing mechanisms defined within the SignedInfo element.
Concerning the different parts of the signature, XAdES specifies what parts of
the signature should be included in such a computattion for each different
time-stamp element defined within XAdES.

Just for your knowledge, currently the Digital Signature Services Technical
Committee
is working on a design of a XML based protocol for requesting time-stamps
issuance
to one server. Such document will also contain a time-stamp token
specification in
XML.  

See details at:

www.oasis-open.org 


Regards

Juan Carlos.

At 12:32 26/01/2004 +0100, A. Jerman Blazic wrote:
>
>Dear All
>
>I don't know whether this was discussed before, but it does impose some
>obstacles in our implementation attempts. We are evaluating the use of
>XAdES as a tool for record archiving system, since XAdES already
>includes some fields for time stamping inclusion. However, the problem
>with time stamping is that is it does not fit into XML structure (so
>far). So XAdES should perfectly perform when using "detach" signature
>type (e.g. file separated from a signature, which can be timestamped
>without problem). But what happens when one uses other signature types?
>How is a time stamping procedure performed when signature is part of a
>(signed) file? Current TimeStamp standard does not recognize an XML
>structure and therefore if time stamped, the part of the message must be
>taken out, time stamped and put back and then timestamp itself included
>in an XAdES structure. It could be performed, but under what
>circumstances? Transformations seems to be the first and the main
>problem not to mention that the whole procedure without clear process
>definition seems pretty awkward, so any suggestions are welcome.
>
>Best regards
>
>Aleksej
>
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Received on Monday, 26 January 2004 07:12:33 UTC