Re: [pkcs11] RE: NIST Special Publication 800-38F

[Michael StJohns <msj@nthpermutation.com>]

On 4/3/2013 6:19 PM, Burns, Robert wrote:
> It would appear that NIST will allow other approved encryption modes, so GCM is a candidate.
Yes.  But it is listed in 2.30 without the wrapping/unwrapping flag (as 
is CCM).  I think if we do modify the mechanism to allow wrapping, we 
probably should provide some guidance on IV/Nonce selection (or allow it 
to be done only internally?)  The nice thing about the AES Keywrap 
algorithm is that the output is fully self-contained - you don't need to 
track an IV or other ancillary data separately.
> In general, I think we should only block inclusions of mechanisms if there are known security issues, and I wasn't able to locate any obvious research on the subject of the AEAD modes as being weaker for key wrap versus data protection.  Anyone know of any prohibitions against using GCM for key wrapping?
I brought this up originally. I *thought* I'd read something suggesting 
that this wasn't an appropriate use of AEAD mechanisms, but I can't find 
it now. That said, I would tend to avoid XOR style key wrap mechanisms 
because they are too easy to get wrong (e.g. duplicate an IV and you can 
compromise a lot of keys) during implementation and use.  The commentary 
in RFC5297 section 1.3.2 is somewhat on point.

Mike

> Bob
>
> > -----Original Message-----
> > From: pkcs11@lists.oasis-open.org [mailto:pkcs11@lists.oasis-open.org] On
> > Behalf Of Lockhart, Robert
> > Sent: Wednesday, April 03, 2013 6:01 PM
> > To: pkcs11@lists.oasis-open.org
> > Subject: [pkcs11] NIST Special Publication 800-38F
> >
> > I took a quick glance and GCM and CCM are in fact only mentioned in the
> > Appendix B as other authenticating modes of operation.  The major
> > difference being that GCM & CCM perform authentication on the encrypted
> > value not the clear text value.
> >
> > http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-38F.pdf
> >
> > This will teach me to re-read the documents before bringing them up.
> >
> > Bob L.
> >
> >
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