Re: [jose] FOR WG DISCUSSION: #82 part A - Possibly changing representation of private JWK fields

I think that the argument below is misleading -- why kind of 
hypothetical key parsing or filtering program is going to read a JWK 
that doesn't know the key types it's parsing out? I'm still not seeing 
the value in having things split out. From my vantage, it seems to be a 
fairly arbitrary syntax decision, and at this point I'd really rather 
not change syntax on stuff I'm already using on a daily basis.

  -- Justin

On 10/01/2013 08:38 PM, Jim Schaad wrote:
>
> There is an argument below that it would be more robust to make any 
> filter software know what is public and what is private since that 
> enforces a per-type evaluation.  However I would argue that this is a 
> problem for any new key type that is published after such filter 
> software is done.
>
> The program which is creating the JWK object is going to know what is 
> public and what is private because it must have been updated in order 
> to export the correct fields for the new key type.  However the filter 
> code may not have been updated to understand this new key type and 
> therefore has no ability to know what is public and what is private 
> unless it was also programmed to do a registry lookup in the IANA 
> registry to figure this out.  Even then it would be unable to deal 
> with private key types.
>
> By placing all private fields in a private object, the filter program 
> would always be able to correct do the filtering and make sure that 
> private key material is not published as it would, by definition, be 
> in a single object which is easily identified.  This means that a 
> server would not need to reject any new key types that it does not 
> understand when trying to make sure that private information is not 
> published.
>
> To me this is more robust than not having this indicated by the 
> exporter functions.
>
> This is similar to what is done today in the ASN.1 case.  The ASN.1 
> structure description is different between the public key and the 
> private key structures for those things you know about.  This makes it 
> easy to do the decode on the public key and ensure that nothing exists 
> that shouldn't.  It is not possible for us to do a filter based just 
> on the public fields since there are other elements that exist in the 
> JWK object which have nothing to do with the key value.  I would not 
> advocate having both a public and a private member object since that 
> would be slightly ridiculous.
>
> Jim
>
> *From:*jose-bounces@ietf.org [mailto:jose-bounces@ietf.org] *On Behalf 
> Of *n-sakimura
> *Sent:* Sunday, September 01, 2013 8:02 PM
> *To:* jose@ietf.org
> *Subject:* Re: [jose] FOR WG DISCUSSION: #82 part A - Possibly 
> changing representation of private JWK fields
>
> +1 Coming in late, all of what I had to say has already been said.
>
> (2013/08/31 8:01), Naveen Agarwal wrote:
>
>     +1 Agree with Mike and Justin's comments.
>
>     On Wed, Aug 28, 2013 at 12:53 PM, Justin Richer <jricher@mitre.org
>     <mailto:jricher@mitre.org>> wrote:
>
>     If the leak is going to happen, it's not going to be on part of
>     the JWK object or JWK set, it's going to be on the whole thing.
>     Stuffing it into a sub-object isn't going to make it any safer in
>     practice. If you want to generate a public key from a
>     public/private pair, you could argue that it'd be simpler to have
>     an outbound thing filter out just the ".private" sub-object as
>     opposed to having something key-specific, but I think the latter
>     is actually more robust against different key types since it
>     enforces a per-type evaluation of what's "public" and what's
>     "private".
>
>     I agree with Mike's contention regarding symmetric keys, below --
>     it's tricky though. In the Nimbus-JOSE-JWT implementation of JWK
>     we've taken the approach of saying that the "public" version of an
>     OctetSequenceKey is null.
>
>     Parallelism on the keying material overall is a good thing though,
>     so I'd prefer to leave it how it is.
>
>      -- Justin
>
>
>
>     On 08/28/2013 03:40 PM, Mike Jones wrote:
>
>     This is a second issue in the issue tracker that I wanted to bring
>     to the working group's attention for discussion.  My personal view
>     is stated in the issue tracker comment below.
>
>                                     -- Mike
>
>     -----Original Message-----
>     From: jose issue tracker [mailto:trac+jose@trac.tools.ietf.org
>     <mailto:trac%2Bjose@trac.tools.ietf.org>]
>     Sent: Wednesday, August 28, 2013 12:36 PM
>     To: draft-ietf-jose-json-web-key@tools.ietf.org
>     <mailto:draft-ietf-jose-json-web-key@tools.ietf.org>; Mike Jones
>     Cc: jose@ietf.org <mailto:jose@ietf.org>
>     Subject: Re: [jose] #82: Section 6. Encrypted JWK and Encrypted
>     JWK Set Format
>
>     #82: Section 6. Encrypted JWK and Encrypted JWK Set Format
>
>     Comment (by michael.jones@microsoft.com
>     <mailto:michael.jones@microsoft.com>):
>
>     This comment is about part A of this issue - the suggestion that
>     private key material within a JWK be moved into a "private"
>     element.  While I  understand the motivation for the suggestion,
>     this doesn't seem like a  necessary or particularly useful change.
>      If an implementation leaks its private or shared key information
>     by disclosing a JWK containing it to a party not entitled to have
>     it, there's no security difference in whether that information is
>     in a top-level member or a member of a "private" field.  The
>     information will have still been inappropriately disclosed.
>
>     This suggestion is also ambiguously specified.  While yes, the "d"
>     elements of elliptic curve and RSA keys could be moved to be
>     within a "private" structure, what would be done for the "k"
>     element of a symmetric key?  Would that also be moved into a
>     "private" element?  (At that point,  there would be no symmetric
>     key information at the top level of the JWK,  which seems more
>     than a little odd.)
>
>     Finally, I'll note that the specs already clearly delineate public
>     from private fields, through use of the Parameter Information
>     Class value in the JSON Web Key Parameters registry (with values
>     "Public" and "Private").  So there should be no confusion which is
>     which.
>
>     I therefore recommend that this suggestion be resolved as "wontfix".
>
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> -- 
> Nat Sakimura (n-sakimura@nri.co.jp  <mailto:n-sakimura@nri.co.jp>)
> Nomura Research Institute, Ltd.
> Tel:+81-3-6274-1412  Fax:+81-3-6274-1547
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