RE: I-D ACTION:draft-ietf-smime-certcapa-02.txt

["Tony Capel" <capel@xxxxxxxxxxx>]

Stefan:

The logic of putting the encryption capabilities in the encryption public key
certificate (and NOT the signing public key certificate) - !I think! - is
straightforward.  My problem is with the capabilities that relate to signing,
should they be in the signing public key certificate?  And for capabilities
relevant for both, should they be in both certs or only one - and which one?
Maybe something like:


"In situations where more than one public key certificate is issued for a single
SMIME entity (e.g. in dual keypair configurations where separate signing and
encryption public key certificates are used) the SMIMECapabilities attributes in
each certificate SHOULD be those which are relevant for the functions associated
with the certificate.

For example, Content Encryption and Key Encryption/Key Transport algorithm
SMIMECapabilities SHOULD be in the encryption public key certificate.  Their
inclusion in the signing public key certificate, while OPTIONAL, would be
redundant, would unnecessarily increase certificate size, and may result in the
need to unnecessarily revoke the certificate if the algorithms are changed
(changes to SMIMECapabilities are discussed in Section 4).

Some SMIMECapabilities, e.g. binary content preferred, compression capabilities
[RFC3274], may be relevant for signing operations as well.  In such cases the
capabilities SHOULD be included in both certificates if the applications using
them do not guarantees the delivery of both certificates.  For example, in
situations where signed messaging is used and encryption public key certificates
are not exchanged (or may not even exist), these attributes SHOULD be provided
in the signing public key certificate (as well)."



Tony



-----Original Message-----
From: owner-ietf-smime@xxxxxxxxxxxx [mailto:owner-ietf-smime@xxxxxxxxxxxx] On
Behalf Of Stefan Santesson
Sent: February 17, 2005 12:06 PM
To: Tony Capel; ietf@xxxxxxxxxxxxxxxxx
Cc: ietf-smime@xxxxxxx
Subject: RE: I-D ACTION:draft-ietf-smime-certcapa-02.txt



Hi Tony,

Would it be sufficient to say that the SMIMECapabilities extension SHOULD only
be included in certificates that support S/MIME encryption?

If not, what would you suggest?


Stefan Santesson
Microsoft Security Center of Excellence (SCOE)
 

> -----Original Message-----
> From: Tony Capel [mailto:capel@xxxxxxxxxxx]
> Sent: den 17 februari 2005 08:38
> To: ietf@xxxxxxxxxxxxxxxxx; Stefan Santesson
> Cc: ietf-smime@xxxxxxx
> Subject: RE: I-D ACTION:draft-ietf-smime-certcapa-02.txt
> 
> Sorry for the incorrect link to comment 3.1, it should be:
> 
> http://www.imc.org/ietf-smime/mail-archive/msg02112.html
> 
> (November 11, 2004 message)
> 
> Tony
> 
> -----Original Message-----
> From: Jim Schaad [mailto:ietf@xxxxxxxxxxxxxxxxx]
> Sent: February 16, 2005 7:37 PM
> To: 'Tony Capel'; 'Stefan Santesson'
> Cc: ietf-smime@xxxxxxx
> Subject: RE: I-D ACTION:draft-ietf-smime-certcapa-02.txt
> 
> 
> Tony,  your linked message makes no sense as it refers to the ESS
update
> not to
> this draft.
> 
> jim
> 
> > -----Original Message-----
> > From: owner-ietf-smime@xxxxxxxxxxxx 
> > [mailto:owner-ietf-smime@xxxxxxxxxxxx] On Behalf Of Tony Capel
> > Sent: Wednesday, February 16, 2005 12:52 PM
> > To: ietf@xxxxxxxxxxxxxxxxx; 'Stefan Santesson'
> > Cc: ietf-smime@xxxxxxx
> > Subject: RE: I-D ACTION:draft-ietf-smime-certcapa-02.txt
> >
> >
> > Stefan:
> >
> > I was happy with the way you addressed most of my Nov 11, 2004 
> > comments, however one comment (3.1) may not have been fully 
> > addressed and is relevant to Jim's:
> >
> > When viewing this draft from the viewpoint of enterprises using 
> > multiple key-pairs (e.g. dual keypairs), some S/MIME Capabilities 
> > should probably be in certain certificates (and optionally or never 
> > in others).  For example, it appears to make no sense to put the 
> > encryption algorithm choices in the signing certificate in 
> > dual-keypair configurations.  Some attributes might be in both certs 
> > (e.g. compression capabilities), however there should also be a note 
> > that for those attributes in both certs they must be the same.
> >
> > So if you make changes to address Jim's comment could I request you 
> > take another look at comment 3.1 in 
> > http://www.imc.org/ietf-smime/mail-archive/msg02117.html
> > - and especially review the revised certcapa text in the contest of 
> > multiple keypair configs where there is more than one public key 
> > certificate corresponding to the entity?
> >
> > Thanks
> >
> > Tony
> >
> > -----Original Message-----
> > From: owner-ietf-smime@xxxxxxxxxxxx 
> > [mailto:owner-ietf-smime@xxxxxxxxxxxx] On Behalf Of Jim Schaad
> > Sent: February 16, 2005 12:46 PM
> > To: ietf@xxxxxxxxxxxxxxxxx; 'Stefan Santesson'
> > Cc: ietf-smime@xxxxxxx
> > Subject: RE: I-D ACTION:draft-ietf-smime-certcapa-02.txt
> >
> >
> >
> > Stefan,
> >
> > I am not really happy with how the following item was addressed.
> >
> > > 2.  I would like to see the addition of a paragraph describing the 
> > > types of capabilities that are expected to be listed.  It
> > seems obious
> > > that bulk encryption algorithms are listed as, potentially, are
key
> > > encryption algorithms (consider RSA-OAEP as an example).
> > However it
> > > is not clear about some of the other potential capabililties.
What
> > > about signature and hash algorithms?  What about MAC algorithms? 
> > > What about S/MIME specifics such as id-cap-preferBinaryInside?
> > >
> >
> > Since I did not care for the paragraph that you have, I am 
> > suggesting the following paragraph instead.
> >
> >
> >
> > There are numerous different types of S/MIME capabilities that have 
> > been defined by different documents.  While all of the different 
> > capabilties can be placed in this attribute, in many cases not all 
> > of them need to be included.  Generally only those items relating to 
> > encryption capabities are included.
> >
> > - Signature/Hash Algorithms: As a general rule, the signature 
> > processing capaiblities of a client are assumed rather than checked, 
> > this means that if they are placed in this extension they may be 
> > ignored.
> >
> > - Content Encryption Algorrithms: This is the general set of 
> > capabities that will be placed in the extension.
> >
> > - Key Encryption/Key Transport Algorithms: These capabilities are 
> > placed in the extension in thoses cases where additional constraints 
> > are placed on the the public key algorithm.  (An example would be 
> > using RSA-OAEP for a generic RSA key.)
> >
> > - MAC Algorithms: These capabilties are genreally omitted from the 
> > extension.
> >
> > - Other capabitlies: This includes such items as binary content 
> > prefered. These capabilties may or may not be generally included
> > depending on wither the item is related to encryption or
> > signature operations.
> >
> >
> >
> >
> >
>