Thanks for the useful review comments, Jim.  Replies inline prefixed by 
"Mike>"...



-----Original Message-----
From: Jim Schaad [mailto:[email protected]]
Sent: Saturday, June 15, 2013 2:08 PM
To: [email protected]
Cc: [email protected]
Subject: Comments on version 11 of draft-ietf-jose-json-web-encryption



Gentlemen,



Here are a few comments for consideration.  Note that some of the comments from 
the JWS review are also applicable to this document as much of the language in 
places is the same.



1.  In Section 4.1.2 - You probably want to say an AEAD algorithm not an AE 
algorithm



Mike> The problem with the "AEAD" terminology is that it implies both algorithm 
and encoding properties.  We want the algorithm properties but not the encoding 
properties defined by RFC 5116.  Thus, a conscious terminology change was made 
in -08 to longer use the term "AEAD".



2  In section 4.1.3 - I would suggest changing the text to "This parameter MUST 
be omitted unless required by the algorithm in the "alg" member.  This header 
parameter MUST be understood if an algorithm is supported that requires it."



Mike> OK



3.  In section 4.1.4 - Does the group agree that compression is a required 
feature to implement?



Mike> This feature was discussed at IETF 83 and has been in place in the 
current form ever since -02.  I'd be shocked if people didn't believe this 
feature was necessary.



4.  Why not reference sections 4.1.5 - 10 by reference with a comment that 
these refer to the key that was used to encrypt the content?  Is there a 
benefit of having them listed here?  Is there a difference in the way they are 
interpreted other than the recipient/originator thing?



Mike> I assume you mean reference them in JWS?  There's a complete list here so 
that it's clear to JWE implementers what the reserved header parameters are 
without having to reference other specs.  And yes, the JWS and JWE key 
selection parameters are the same other than the JWS sender/JWE receiver 
difference.



5.  Why not reference sections 4.1.11-12 from the JWS document?  Is there a 
difference in the way they are interpreted?



Mike> (Apparently I didn't understand what you were suggesting in 4, having 
seen this next question.)  In any event, in JWS they reference the key that is 
used to verify the signature.  In JWE they reference the key to which the 
content was encrypted.  That's the difference in all these parameters.



6.  If we are not going with an alphabetic order of names, the I would suggest 
that apu should be next to exp as they are used in the same context and 
therefore having them adjacent makes sense.



Mike> Actually, Richard had suggested moving "apu" to the key agreement section 
in JWA, since its use is algorithm-specific.  I think I agree with him.



7.  Is there a reason not to reference 4.1.14 from JWS?  Is there a difference 
in interpretation?



Mike> Stylistically, it seems easier for implementers of JWE to have a complete 
list of general-purpose parameter definitions than to have some here and some 
there.  The example is also different, because one is a JWS header and the 
other is a JWE header.



                                                                Thanks again,

                                                                -- Mike



Jim




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