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Subject: RE: [dss] ANSI X9.95 and timestamping profile
Juan Carlos, Dimitri, I would prefer to avoid changing the TSTInfo structure just for this requirement. It would be preferable to use an approach which can be handled using the existing extension mechanisms. Nick > -----Original Message----- > From: Juan Carlos Cruellas [mailto:cruellas@ac.upc.edu] > Sent: 04 February 2005 09:00 > To: Dimitri Andivahis > Cc: dss@lists.oasis-open.org; Nick Pope; Trevor Perrin > Subject: Re: [dss] ANSI X9.95 and timestamping profile > > > Dimitri, > > First of all a perhaps silly question...sorry if > it actually is... > Is there any rationale behind that advices to > just renew the time-stamp instead re-timestamping > the document or even generate a new time-stamp for > both depending on the context or is it > just a way of offering different alternatives to the > market and let it decide?. > > Just as an example, in XAdES for instance, > when we have to renew timestamps for signatures > long term archiving, we generate > a new timestamp that includes both certain > elements of the signature itself and previously generated > timestamps.... > > Concerning the details on how to deal with the > technicalities in XML.... > I have understood (but perhaps not correctly) > you propose two alternatives: > 1. To add the old token as the second child. So that you > are sugesting to have a <ds:Signature> as the child of > the <ds:Signature>/<ds:Object> just generated.... > So this would imply that each renewal of the time-stamp > would imply increase the level of depth at which you would > have ds:Signature corresponding to former time-stamps... > Have I correctly understood it?. > > 2. To add the old token within the <dss:TSTInfo> so in the > end, the most recently token would be a <ds:Signature> with > a <dss:TSTInfo> that in its turn would have a <ds:Signature> > with another <dss:TSTInfo> with another <ds:Signature> and so on > > Well, certainly the alternative 1 somehow makes visible at the > level of the signature itself the details of the linking in time > between the token and those previously generated. The second > one just encloses these details within the <dss:TSTInfo>, and > the management of all the information of previous tokens would > be conceptually linked to the processing of <dss:TSTInfo>. I would > say that if we go on with this work, I would be more in favour of > this last one. > > Regards > > Juan Carlos. > > Dimitri Andivahis wrote: > > >Trevor, Nick, > > > >This method can be used to assert integrity and time of existence > >of a document in long term archives, while at the same time > >it maintains a clear distinction between the document itself > >(possibly containing electronic signatures) and the collected > >timestamping information about it. Renewing a timestamp token > >for a given document results in a newly generated timestamp > >token that takes the place of the previous timestamp token. > > > >This method has been included in ANSI X9.95, ISO/IEC 18014-2, > >and ISO/IEC 18014-3. I expect it will be practiced by vendors who > >follow these standards. It is general enough in scope that > >it could be applied to any type of timestamp token, and it can > >be used to support renewal of legacy tokens using XML timestamp tokens. > >If the types and processing rules for supporting the renewal method > >in XML timestamp tokens are defined with some care, it can allow > >for a mix of any XML timestamp token types in the "Russian doll > structure". > > > >There are different possible ways to implement this method within > >the DSS timestamping profile. One possibility that agrees well > >with the protocols in ANSI X9.95 is to specify the previous token > >in a sign request via a new optional input such as RenewTimestamp: > > > ><xs:element name="RenewTimestamp"> > > <xs:complexType> > > <xs:sequence> > > <xs:element ref="dss:Timestamp"> > > <xs:sequence> > > </xs:complexType> > ></xs:element> > > > >that carries the previous timestamp token. > > > >The service generating the renewal token need make no assertions > >about the validity of the previous token submitted to it. The client > >must verify that the previous token matches the document(s) of interest, > >and the client should verify that the previous token is presently > >valid at the time of renewal. > > > >For XML processing rules for <ds:signature>, if this optional input > >is present, the service must include the previous token as > >the second child element of <ds:Signature>/<ds:Object> in the > >generated renewal token and cover it with the signature. Currently, > ><TstInfo> is the only specified child element of > <ds:Signature>/<ds:Object>. > >[Alternatively, we could update the definition of the <TstInfo> type > >and add the previous token as a child element of <TstInfo>. > >This would keep all information about time values within <TstInfo> > >and would be more in line with the claim that the time value > >in the innermost token is the asserted value of existence.] > > > >For CMS processing rules, it would be best to let sub-profiles > >specify a solution that is appropriate for their needs. For example, > >CMS services compatible with ANSI X9.95 may or may not require that > >the submitted previous token be an ANSI X9.95 compliant token, > >and they would place the previous token as an extension within > >the CMS TSTInfo structure of the newly generated renewal token. > > > >Services that do not support renewal requests would just return > >a NotSupported result code. > > > >For verify requests, the service need only verify the outer token > >and not deal with the inner previous token(s). To completely verify > >a renewal token and assert the time value in the innermost > (oldest) token, > >the client must access each successive inner token and submit > >for each one a verify request that also specifies the time of issuance > >of its immediately enclosing token. To that effect, the DSS > timestamping > >profile needs to allow the VerificationTime additional input in verify > >requests. > > > >Dimitri > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dss-unsubscribe@lists.oasis-open.org > For additional commands, e-mail: dss-help@lists.oasis-open.org > > >
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