Re: [OAUTH-WG] Proof-of-Possession Key Semantics for JWTs spec addressing final shepherd comment

[John Bradley <[e-mail]>]

OK, no good reason unless the client is using a HSM that can do HMAC and can export a symmetric key wrapped in a asymmetric key provided by the AS.

We don’t currently cover that use case of sending a wrapped symmetric key to the AS in POP key distribution.   
I don’t know how common that is going to be, but it is worth thinking about defining.

John B.

> On Nov 5, 2015, at 1:45 PM, Anthony Nadalin <[e-mail]> wrote:
> 
> Not sure why you think its weaker as it would be a wrapped key that the hardware produces 
> 
> -----Original Message-----
> From: OAuth [mailto:[e-mail]] On Behalf Of John Bradley
> Sent: Wednesday, November 4, 2015 8:43 PM
> To: Justin Richer <[e-mail]>
> Cc: <[e-mail]> <[e-mail]>
> Subject: Re: [OAUTH-WG] Proof-of-Possession Key Semantics for JWTs spec addressing final shepherd comment
> 
> In the asymmetric case the use of a HSM or secure element is the argument for the client selecting the public key.   In those cases the client is doing the key gen in hardware so one hopes it is OK.   In the symetric case the client generating the key is weaker (as in I can’t think of any really good reason).
> 
> 
>> On Nov 5, 2015, at 1:35 PM, Justin Richer <[e-mail]> wrote:
>> 
>> I’d argue that it’s best practice, and in line with other parts of OAuth, if we assume the server generates it in the normal case (issuer -> presenter). Client generated token keys should be an exception, especially in the asymmetric case.
>> 
>> — Justin
>> 
>>> On Nov 5, 2015, at 1:32 PM, John Bradley <[e-mail]> wrote:
>>> 
>>> Agreed the only real difference is the quality of the key.  If the server generates it, then it knows that the client is not using the fixed hex value of DEADBEEF for everything.
>>> 
>>> John B.
>>>> On Nov 5, 2015, at 9:25 AM, Hannes Tschofenig <[e-mail]> wrote:
>>>> 
>>>> I agree that the effect is the same. From a security point of view 
>>>> there is only an impact if one of the two parties is in a better 
>>>> position to generate random numbers, which is the basis for 
>>>> generating a high entropy symmetric key.
>>>> 
>>>> On 11/04/2015 11:51 PM, Mike Jones wrote:
>>>>> Thanks for the detailed read, Brian.  You’re right that in the 
>>>>> symmetric case, either the issuer or the presenter can create the 
>>>>> symmetric PoP key and share it with the other party, since the effect is equivalent.
>>>>> I suspect that both the key distribution draft and this draft 
>>>>> should be updated with a sentence or two saying that either 
>>>>> approach can be taken.  Do others concur?
>>>>> 
>>>>> 
>>>>> 
>>>>>                                                         -- Mike
>>>>> 
>>>>> 
>>>>> 
>>>>> *From:*Brian Campbell [mailto:[e-mail]]
>>>>> *Sent:* Thursday, November 05, 2015 7:48 AM
>>>>> *To:* Mike Jones
>>>>> *Cc:* Kepeng Li; [e-mail]
>>>>> *Subject:* Re: [OAUTH-WG] Proof-of-Possession Key Semantics for 
>>>>> JWTs spec addressing final shepherd comment
>>>>> 
>>>>> 
>>>>> 
>>>>> +1 for the diagrams making the document more understandable.
>>>>> 
>>>>> One little nit/question, step 1 in both Symmetric and Asymmetric 
>>>>> keys shows the Presenter sending the key to the Issuer. It's 
>>>>> possible, however, for the key to be sent the other way. Presenter 
>>>>> sending it to the Issuer is probably preferred for asymmetric, 
>>>>> especially if the client can secure the private keys in hardware. 
>>>>> But I don't know if one way or the other is clearly better for 
>>>>> symmetric case and PoP key distribution currently has it the other 
>>>>> way <https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2ftools.ietf.org%2fhtml%2fdraft-ietf-oauth-pop-key-distribution-02%23section-4.2&data=01%7c01%7ctonynad%40microsoft.com%7c9456670075d04a51f85508d2e59ba294%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=UgZEoqQiaUk9VdYpSQRvUeVVOQgIUg3UmAr18oQ7GtI%3d>.
>>>>> Should the intro text somehow mention the possibility that the 
>>>>> Issuer could create the key and send it to the Presenter?
>>>>> 
>>>>> I know it's only the introduction but it was just something that 
>>>>> jumped out at me.
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> On Wed, Nov 4, 2015 at 9:04 AM, Mike Jones 
>>>>> <[e-mail] <mailto:[e-mail]>> wrote:
>>>>> 
>>>>> Thanks for suggesting the diagrams, Kepeng. They make the document 
>>>>> more understandable.
>>>>> 
>>>>> -- Mike
>>>>> 
>>>>> -------------------------------------------------------------------
>>>>> -----
>>>>> 
>>>>> *From: *Kepeng Li <mailto:[e-mail]>
>>>>> *Sent: *‎11/‎5/‎2015 12:57 AM
>>>>> *To: *Mike Jones <mailto:[e-mail]>; 
>>>>> [e-mail] <mailto:[e-mail]>
>>>>> *Subject: *Re: Proof-of-Possession Key Semantics for JWTs spec 
>>>>> addressing final shepherd comment
>>>>> 
>>>>> Thank you Mike.
>>>>> 
>>>>> 
>>>>> 
>>>>> The diagrams look good to me.
>>>>> 
>>>>> 
>>>>> 
>>>>> Kind Regards
>>>>> 
>>>>> Kepeng
>>>>> 
>>>>> 
>>>>> 
>>>>> *发件人**: *Mike Jones <[e-mail] 
>>>>> <mailto:[e-mail]>>
>>>>> *日期**: *Thursday, 5 November, 2015 12:32 am
>>>>> *至**: *"[e-mail] <mailto:[e-mail]>" <[e-mail] 
>>>>> <mailto:[e-mail]>>
>>>>> *抄送**: *Li Kepeng <[e-mail] 
>>>>> <mailto:[e-mail]>>
>>>>> *主题**: *Proof-of-Possession Key Semantics for JWTs spec addressing 
>>>>> final shepherd comment
>>>>> 
>>>>> 
>>>>> 
>>>>> Proof-of-Possession Key Semantics for JWTs draft -06 addresses the 
>>>>> remaining document shepherd comment – adding use case diagrams to 
>>>>> the introduction.
>>>>> 
>>>>> 
>>>>> 
>>>>> The updated specification is available at:
>>>>> 
>>>>> ·        https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2ftools.ietf.org%2fhtml%2fdraft-ietf-oauth-proof-of-possession-06&data=01%7c01%7ctonynad%40microsoft.com%7c9456670075d04a51f85508d2e59ba294%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=6hE6dOO0I1%2ffF005rVknyOFHuB18gdpZg9dftExLtCw%3d
>>>>> 
>>>>> 
>>>>> 
>>>>> An HTML formatted version is also available at:
>>>>> 
>>>>> ·       
>>>>> https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fse
>>>>> lf-issued.info%2fdocs%2fdraft-ietf-oauth-proof-of-possession-06.htm
>>>>> l&data=01%7c01%7ctonynad%40microsoft.com%7c9456670075d04a51f85508d2
>>>>> e59ba294%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=EQd4rUcuyqdSP
>>>>> gmibtcfjMpJm6RWWwCZC85%2bCboEs54%3d
>>>>> 
>>>>> 
>>>>> 
>>>>>                                                         -- Mike
>>>>> 
>>>>> 
>>>>> 
>>>>> P.S.  This note was also posted at 
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>>>>> 
>>>>> 
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