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

From: [email-masked] (Peter Gutmann)
Date: Tue, 10 Apr 2007 22:56:02 +1200

Russ Housley <[email-masked]> writes:

>On the first item, you never sent text.  

Oh, I thought that what I'd sent you was enough to go on.  Looks like it was
just a communications problem then, I'll try and get you something soonish.

>On the second item, I disagree.  The authenticated attributes are handled the
>same as in AuthenticatedData. 

They're placed before the data, not after it, which is unlike any other use of
authenticated attributes in any CMS PDU.  As both Peter Sylvester and myself
have already pointed out, this makes one-pass/streaming processing impossible.

Peter.

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From: Russ Housley <[email-masked]>
Date: Tue, 10 Apr 2007 08:48:58 -0400

>have already pointed out, this makes one-pass/streaming processing impossible.

As I already said in response, AES-CCM and AES-GCM both require the 
processing of the "additional authenticated data" (the authenticated 
attributes in this structure) prior to the processing of the payload 
(the encapsulated content in this structure).  Thus, the only way 
that one-pass processing can be accomplished with these authenticated 
encryption modes is for the authenticated attributes to appear first.

Russ