PS I did resist the temptation of doing DH key agreement in the Authorization 
request /response then using the agreed key as the code proof.
That would also be secure but not popular with developers.

John B.

On Nov 9, 2013, at 7:51 AM, John Bradley <[email protected]> wrote:

> With a native app using a captive browser with no malware, only the response 
> is susceptible to interception, making encrypting the request redundant.
> In other environments and with some user groups the request's challenge needs 
> to be protected from interception.  This may be more the case in a desktop 
> environment where there is less control over the browser.
> 
> I expect that we will come to two options one unprotected requests and one 
> for protected requests.
> 
> To Phil's point this is not about identifying the class of software this is 
> about matching a response to an instance of software.   
> A software statement gives you a hint about the class of software but not the 
> instance without per client registration.
> 
> This method gives you the ability to securely return the token to only the 
> instance of the client that requested it without the overhead of per instance 
> dynamic registration.
> 
> This is a practical solution to a real problem people are having today, and 
> versions of this are in production now.   
> 
> Nat and I are trying to document it so that there can be interoperability 
> rather than every AS doing something different.
> 
> John B.
> 
> On Nov 9, 2013, at 5:23 AM, Torsten Lodderstedt <[email protected]> 
> wrote:
> 
>> Hi Nat,
>> 
>> what's the rationale for having different algorithms to produce a code 
>> challenges? As this may cause interop issues there should be good reasons to 
>> introduce variants.
>> 
>> regards,
>> Torsten.
>> 
>> 
>> Am 19.10.2013 12:15, schrieb Nat Sakimura:
>>> Incorporated the discussion at Berlin meeting and after in the ML. 
>>> 
>>> Best, 
>>> 
>>> Nat
>>> 
>>> ---------- Forwarded message ----------
>>> From: <[email protected]>
>>> Date: 2013/10/19
>>> Subject: New Version Notification for draft-sakimura-oauth-tcse-02.txt
>>> To: Nat Sakimura <[email protected]>, John Bradley 
>>> <[email protected]>, Naveen Agarwal <[email protected]>
>>> 
>>> 
>>> 
>>> A new version of I-D, draft-sakimura-oauth-tcse-02.txt
>>> has been successfully submitted by Nat Sakimura and posted to the
>>> IETF repository.
>>> 
>>> Filename:        draft-sakimura-oauth-tcse
>>> Revision:        02
>>> Title:           OAuth Symmetric Proof of Posession for Code Extension
>>> Creation date:   2013-10-19
>>> Group:           Individual Submission
>>> Number of pages: 8
>>> URL:             
>>> http://www.ietf.org/internet-drafts/draft-sakimura-oauth-tcse-02.txt
>>> Status:          http://datatracker.ietf.org/doc/draft-sakimura-oauth-tcse
>>> Htmlized:        http://tools.ietf.org/html/draft-sakimura-oauth-tcse-02
>>> Diff:            
>>> http://www.ietf.org/rfcdiff?url2=draft-sakimura-oauth-tcse-02
>>> 
>>> Abstract:
>>>    The OAuth 2.0 public client utilizing authorization code grant is
>>>    susceptible to the code interception attack.  This specification
>>>    describe a mechanism that acts as a control against this threat.
>>> 
>>> 
>>> 
>>> 
>>> 
>>> Please note that it may take a couple of minutes from the time of submission
>>> until the htmlized version and diff are available at tools.ietf.org.
>>> 
>>> The IETF Secretariat
>>> 
>>> 
>>> 
>>> 
>>> -- 
>>> Nat Sakimura (=nat)
>>> Chairman, OpenID Foundation
>>> http://nat.sakimura.org/
>>> @_nat_en
>>> 
>>> 
>>> _______________________________________________
>>> OAuth mailing list
>>> [email protected]
>>> https://www.ietf.org/mailman/listinfo/oauth
>> 
>> _______________________________________________
>> OAuth mailing list
>> [email protected]
>> https://www.ietf.org/mailman/listinfo/oauth
> 

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