Subject: [jose] MTI algorithms

From: Richard Barnes <[email-masked]>
Date: Thu, 14 Mar 2013 09:36:24 -0400

I noted yesterday a concern that many things that should be counted as JOSE
implementations could actually be ruled out if we have MTI algorithms.

The concern arises from the fact that JOSE libraries are built on crypto
libraries -- they are not crypto libraries, and thus they don't necessarily
control what algorithms are available.  The WebCrypto example is one flavor
of this: If I write a JOSE library that uses WebCrypto, then I have *no*
*idea* what algorithms will be available when my library is run in a
browser.  Since I can't guarantee that MTI algorithms will be available, I
can't be counted as a JOSE implementation.  This is not just a WebCrypto
issue.  It could appear just as easily if I link against OpenSSL, which has
famously varied support for things like ECC.  Or if I use PKCS#11 to talk
to smart cards -- who knows whether the smart card that's inserted right
now has an RSA engine?

Given these scenarios, the MUST in the MUST IMPLEMENT would be a
"Schrödinger's MUST" -- a library's compliance can't be determined until
it's run.  This does not seem like a useful requirement.

I also don't accept the notion that the IESG will not accept a document
without an MTI algorithm suite.  (And not just because of recent events.)
 In addition to the argument above, there's history; namely, that CMS
doesn't have any MTIs.

Much like several other questions in this group, this is a layering
question.  JOSE is not a crypto spec, and it's not an application.  It's an
encoding of crypto parameters, which is used by applications.  So our focus
here should be on clear expression of the relevant parameters, in a way
that is useful to applications -- not on trying to force application
behaviors.

---

From: Leif Johansson <[email-masked]>
Date: Thu, 14 Mar 2013 14:54:09 +0100

On 03/14/2013 02:36 PM, Richard Barnes wrote:
> I noted yesterday a concern that many things that should be counted as
> JOSE implementations could actually be ruled out if we have MTI
> algorithms.  
>
>
Richard I think you're overcomplicating things.

Yes, in principle you're right about the WebCrypto example and yes you
might be
right about CMS (although that was some time ago) but you have to ask
yourself
is this really worth picking a fight over?

        Cheers Leif

---

From: Richard Barnes <[email-masked]>
Date: Thu, 14 Mar 2013 09:57:38 -0400

> is this really worth picking a fight over?

I'm not going to go to the mat on this.  I just wanted to state clearly why
I think the MTI idea is so vacuous.

--Richard

---

From: Leif Johansson <[email-masked]>
Date: Thu, 14 Mar 2013 14:58:30 +0100

On 03/14/2013 02:57 PM, Richard Barnes wrote:
> I'm not going to go to the mat on this.  I just wanted to state
> clearly why I think the MTI idea is so vacuous.
>
> --Richard 
I think we've all felt that way once or twice. I know I have.

---

From: Richard Barnes <[email-masked]>
Date: Fri, 15 Mar 2013 13:13:11 -0400

If you're going to do that, you might as well punt entirely, since an
application could define its own "JOSE crypto profile".  Which would be
fine with me; I think it's the applications that should be defining this
stuff anyway.
--Richard

On Thu, Mar 14, 2013 at 3:46 PM, Steffen Yount <[email-masked]> wrote:

>  Would it be better to keep MTI out of the jose container specs, by
> declaring jose crypto profiles separately, where jose libraries that want
> to claim “jose compliance” would have to meet the MTIs as defined in those
> jose crypto profiles?****
>
> ** **
>
>   ****
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> ** **
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> ** **
>
> ** **
>
> *From:* [email-masked] [mailto:[email-masked]] *On Behalf
> Of *Leif Johansson
> *Sent:* Thursday, March 14, 2013 6:59 AM
> *To:* Richard Barnes
> *Cc:* [email-masked]
> *Subject:* Re: [jose] MTI algorithms****
>
> ** **
>
> On 03/14/2013 02:57 PM, Richard Barnes wrote:****
>
> ** **
>
> >****
>         Cheers Leif****
>  ** **
> I'm not going to go to the mat on this.  I just wanted to state clearly
> why I think the MTI idea is so vacuous.****
>
> ** **
>
> --Richard ****
>
> I think we've all felt that way once or twice. I know I have.****
>