Re: I-D ACTION:draft-ietf-smime-cms-auth-enveloped-03.txt

Jim Schaad wrote:
> Yes I agree that would be a problem,  can you suggest an attribute which
> might need to be placed there that would have this attribute?  Currently the
> only one I could think of is a digest which is not needed as this is dealt
> with by the encryption algorithm.
>   
A time stamp, or something like a the 3 level wrapper of ESS to be 
extracted from
some data that are structured, i.e. you would have an appliance that streams
end encrypts and adds a resume.
> I don't need a real one, but I want to have some inkling that this MIGHT be
> a real problem before trying to solve it.
>   
See above. I am not sure but I always had the impression that the 
possibility of streaming
is one of the fundamental features. If now we have an algorithm that 
does allow this
in a reasonable, i.e. for example by splitting the message into chained 
chunks that
can be authenticated (almost) on the fly and do not require an 
undeterminable
size limit. requiring several mega of storage is not acceptable for 
processing smime
message is not acceptable IMO.

> Jim
>
>
>   
> > -----Original Message-----
> > From: pgut001 [mailto:pgut001(_at_)cs(_dot_)auckland(_dot_)ac(_dot_)nz]
> > Sent: Wednesday, April 25, 2007 1:55 PM
> > To: housley(_at_)vigilsec(_dot_)com; ietf(_at_)augustcellars(_dot_)com;
> > pgut001(_at_)cs(_dot_)aucKland(_dot_)ac(_dot_)nz
> > Cc: ietf-smime(_at_)imc(_dot_)org
> > Subject: RE: I-D ACTION:draft-ietf-smime-cms-auth-enveloped-03.txt
> >
> > "Jim Schaad" <ietf(_at_)augustcellars(_dot_)com> writes:
> >
> >     
> > > I am having a problem seeing why having the attributes first causes a
> > > problem for algorithms that want them second.  All that is needed is
> > >       
> > that
> >     
> > > the encryption wrapper for the code understand that the attributes are
> > >       
> > going
> >     
> > > to come in first and hold onto them until later.  This is assuming
> > >       
> > that the
> >     
> > > encryption wrapper understands the difference between the body and the
> > > attributes.
> > >       
> > What if the attributes depend on the data being processed (as Peter
> > Sylvester
> > pointed out)?  By putting them first, you can't emit the first byte of
> > data
> > until you've processed every other byte of data.  This is why current
> > CMS
> > practice puts the attributes last.
> >
> > Peter.
> >     
>
>

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