Can one of you please expand on "Why not EKU?" (Since I included it in
all the ECC stuff, if there's a good reason why not, maybe we can change
things.) Naively it seems like EKU has a bunch of nice properties . for
example you can use it to place the policy decision on the private key
holder or the public key holder with the criticality flag, you can
acknowledge that using keys with multiple algs happens and at least make
you the keys are only used with the OIDs listed, you have a reasonable
migration path by making the extension non-critical initially, etc. Is
it just lack of support for EKU in PKI products that makes introducing a
new OID in subjectPublicKeyInfo desirable?
Best regards. simon
-----Original Message-----
From: owner-ietf-smime(_at_)mail(_dot_)imc(_dot_)org
[mailto:owner-ietf-smime(_at_)mail(_dot_)imc(_dot_)org] On Behalf Of Robert
Zuccherato
Sent: Friday, August 02, 2002 9:41 AM
To: 'Housley, Russ'; ietf-smime(_at_)imc(_dot_)org
Subject: RE: RSA OAEP Public Key Identification
Russ;
I think that including the id-RSAES-OAEP be used in the certificate
subject public key info field is the right way to go. The only other
option that I see is Extended Key Usage, but I don't think that EKU was
meant to deal with algorithm usages.
I do have one question though. If we go with your proposal, how would
certificates with rsaEncryption in the SubjectPublicKeyInfo
AlgorithmIdentifier be treated? My suggestion would be that any key
transport method (PKCS #1, OAEP, etc) could be used with these keys.
Anything else would be a redefinition of what that OID meant. Also,
this would allow people who want to use both algorithms with one key to
continue to do so. This would mean that id-RSAES-OAEP need only be
included in the subject public key info of certificates whose key is to
be used solely with OAEP, for everyone else nothing changes.
Robert.
-----Original Message-----
From: Housley, Russ [mailto:rhousley(_at_)rsasecurity(_dot_)com]
Sent: Thursday, August 01, 2002 5:01 PM
To: ietf-smime(_at_)imc(_dot_)org
Subject: RSA OAEP Public Key Identification
At the meeting in Yokohama, we discussed the RSA OAEP draft.
One of the
areas that was discussed was the security considerations
section, where the
document recommends that a key pair only be used for one
purpose. Presently, we do not have a mechanism for
identifying how a key
holder would like to have their public key used.
The certificate currently tells the message originator that
the public key
is an RSA key, and the key usage extension tells that the
public key can be
used for key transport. There is nothing to tell the message
originator
whether RSA PKCS #1 v1.5 or RSA OAEP ought to be used with a
particular
key. So, there is no indication to the message originator
that will allow
the security consideration to be implemented.
Here is my proposed solution: use a different algorithm
identifier in the
certificate.
I suggest that the id-RSAES-OAEP be used in the certificate
subject public
key info field to indicate that the public key should ONLY be
used with RSA
OAEP.
This proposal may make transition from RSA PKCS #1 v1.5 to
RSA OAEP a bit
more difficult, since it would not allow one key pair to be
used with both
algorithms. However, this is exactly what the security
considerations
recommend.
Does anyone have concerns with this approach?
If this approach is adopted, then a companion document in the
PKIX working
group for the proper handling of RSA OAEP (and probably RSA
PSS) public
keys will likely be needed.
Russ