Re: [jose] Stephen Farrell's Discuss on draft-ietf-jose-json-web-algorithms-33: (with DISCUSS and COMMENT)

Stephen Farrell <stephen.farrell@cs.tcd.ie> Tue, 21 October 2014 12:33 UTC

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Subject: Re: [jose] Stephen Farrell's Discuss on draft-ietf-jose-json-web-algorithms-33: (with DISCUSS and COMMENT)
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Hi Mike,

Just on my one remaining discuss point which is about
RSA key pairs where the modules has >2 prime factors
and the "oth" field...

On 14/10/14 13:51, Mike Jones wrote:
> The proposed resolutions have been incorporated in the -34 draft.  Hopefully you'll be able to clear your DISCUSSes on that basis.
> 
> Note that I did manage to come up with some guidance to the designated experts about performing reasonable due diligence on registered algorithms in Section 7.1.  References were added backing lots of the previously mysterious statements about key sizes, etc. as well.
> 
> 				Thanks again,
> 				-- Mike
> 
>> -----Original Message-----
>> From: jose [mailto:jose-bounces@ietf.org] On Behalf Of Mike Jones
>> Sent: Monday, October 06, 2014 12:54 AM
>> To: Stephen Farrell; The IESG
>> Cc: jose-chairs@tools.ietf.org; jose@ietf.org; draft-ietf-jose-json-web-
>> algorithms@tools.ietf.org
>> Subject: Re: [jose] Stephen Farrell's Discuss on draft-ietf-jose-json-web-
>> algorithms-33: (with DISCUSS and COMMENT)
>>
>> Thanks for your review, Stephen.  I've included the working group on the thread
>> so they're aware of your comments.
>>
>>> -----Original Message-----
>>> From: Stephen Farrell [mailto:stephen.farrell@cs.tcd.ie]
>>> Sent: Thursday, October 02, 2014 3:37 AM
>>> To: The IESG
>>> Cc: jose-chairs@tools.ietf.org; draft-ietf-jose-json-web-
>>> algorithms@tools.ietf.org
>>> Subject: Stephen Farrell's Discuss on draft-ietf-jose-json-web-algorithms-33:
>>> (with DISCUSS and COMMENT)
>>>
>>> Stephen Farrell has entered the following ballot position for
>>> draft-ietf-jose-json-web-algorithms-33: Discuss
>>>
>>> When responding, please keep the subject line intact and reply to all
>>> email addresses included in the To and CC lines. (Feel free to cut
>>> this introductory paragraph, however.)
>>>
>>>
>>> Please refer to
>>> http://www.ietf.org/iesg/statement/discuss-criteria.html
>>> for more information about IESG DISCUSS and COMMENT positions.
>>>
>>>
>>> The document, along with other ballot positions, can be found here:
>>> http://datatracker.ietf.org/doc/draft-ietf-jose-json-web-algorithms/
>>>
>>>
>>>
>>> ----------------------------------------------------------------------
>>> DISCUSS:
>>> ----------------------------------------------------------------------
>>>
>>>
>>> Sorry to pile on, but I guess such a detailed and broad piece of work
>>> is likely to attract many comments and discusses.
>>> Mine should be cleared up easily enough I hope.
>>>
>>> (1) 6.3.2.7: Hmm, where was that discussed on the list?  I think it'd
>>> be better if >2 prime RSA was considered a separate algorithm. (I
>>> vaguely recall some IPR with such moduli for some uses too, but not
>>> sure.) I'd recommend dropping the whole "oth" parameter entirely.
>>> (I'll clear this discuss once its clear that this was discussed by the
>>> WG, I just want to check as I don't recall it.)
>>
>> This was discussed in the thread "private keys, leading zeros" initiated by James
>> Manger on August 15, 2012.  (Sorry, I can't get you the archive URL reference at
>> present because I'm writing this offline on an airplane over the Pacific.)  It was
>> also discussed as issue #153.  This feature was directly modelled on RFC 3447.
>> Applications are free to profile the JWK spec to prohibit the use of such keys, so
>> I don't see a compelling case to remove it.

Well that was a modest dicussion wasn't it - James said, "hey
what about >2 primes?" and you said "yurgh, do we need it or
is that theoretical?" and that was it.

I understand the reluctance to drop it now but would like to
check if the WG want to keep this or not as I'd not be at all
surprised if few or none had code or had thought much about
it. I'd equally not be surprised if some code did exist. I
would be surprised if lots of well-tested code existed:-)

Cheers,
S.

PS: I didn't scan the comments.

>>
>>> (2) Instructions to DEs: would registering DES be considered ok or
>>> not? What about myJustInventedPrivateAlg?  What about a request for 10
>>> ccTLD specific Algs? I think these need a bit more clarity wrt
>>> cryptographic "goodness." As a nit, "makes sense" isn't going to help
>>> too much, we've seen that reasonable folks can differ on that here.
>>> Again I don't recall that discussion on the list, but please point me at it if it
>> happened.
>>
>> Registering DES with the Implementation Requirements value "Prohibited"
>> would be permitted.  The instructions on the "JOSE Implementation
>> Requirements" registry field include:
>>     Any identifiers registered for non-authenticated encryption algorithms
>>     or other algorithms that are otherwise unsuitable for direct use
>>     as JWS or JWE algorithms must be registered as "Prohibited".
>>
>> Note that this capability was added at the request of the W3C WebCrypto WG.
>> (WebCrypto is choosing to support some algorithms that JOSE explicitly chose
>> not to, including some non-authenticated encryption algorithms.)  "Deprecated"
>> is also a value available to registrants and the DEs.
>>
>> If you want to supply additional proposed language to the DEs, that would be
>> welcomed.
>>
>>> ----------------------------------------------------------------------
>>> COMMENT:
>>> ----------------------------------------------------------------------
>>>
>>>
>>> - Unlike others, I do think implementation requirements are needed.
>>> The WG did specifically discuss this (a lot) and landed where it did.
>>> I don't think the IESG should second guess that without specific evidence that
>> it'd cause damage.
>>> (Richard's points were made previously I believe.)
>>
>> I concur with your synopsis of the discussion that occurred in the working group
>> and the conclusions reached.
>>
>>> - 3.3 (and elsewhere) says 2048 bits or larger. I guess that
>>> 2049 bit keys might not work for many implementations and are not a
>>> great idea (as Bleichenbacher works quicker against such lengths if I
>>> recall correctly). Could be worth a note somewhere even though I guess most
>> folks know what's what.
>>
>> Rather than us inventing new text, is there an RFC or other doc we can reference
>> that provides appropriate guidance on acceptable RSA key lengths?  I know that
>> the 2048 came from NIST key usage requirements that I believe ekr pointed us
>> to.
>>
>>> - 4.1 (and elsewhere): adding table captions with numbers would be good.
>>
>> I don't feel strongly about this, but each table is in its own section, and so can be
>> referenced by section number.  I'd experimented with adding captions at one
>> point and it just seemed to take up additional vertical space without making the
>> spec clearer.  But I could be convinced otherwise.  Why do you want captions?
>>
>>> Col 1 of the final 3 rows are unfortunate.
>>
>> I don't know how to teach xml2rfc to not do what it did to the final 3 rows, but I
>> can make a note to have the RFC editor manually address this if the tool can't.
>>
>>> - Surprised there was no need for integer DH. Can be added later I guess.
>>
>> No one has previously asked about it.  But there registry will be there for it to be
>> added, if wanted/needed.
>>
>>> - 6.2.1: Given that the point compression IPR is now expired
>>> (right?) did the WG consider now allowing that? I wondered how much
>>> work it would be to add now, vs to add later. If "later" would cause a
>>> lot of duplication, then maybe "now"
>>> would actually be worth it. ("Later" might also be fine considering
>>> the current work in CFRG on additional curves.)
>>
>> I recall that in the discussions, people were happier having a single
>> representation than multiple representations.  Given the curve discussions, that's
>> also another reason I'd opt for "later".
>>
>>> - 6.3.1.1: allowing the extra 0x00 would be a better choice IMO, but whatever.
>>> Those were historically added so that buggy decoders wouldn't wrongly
>>> think numbers negative, which could still happen maybe.
>>
>> Yeah, I realize why the Java library does this.  This was another case where we
>> decided that having a single representation would create less interop problems
>> down the road than allowing multiple representations.
>>
>>> - 7.1, 2nd para: why not RSA2048 earlier then?
>>
>> I don’t actually recall.  I think the two choices reasonably available to us at this
>> point are to either keep or delete this paragraph.  Which would you prefer?
>>
>>> - 7.1.1: It might help the DE if the template here required references
>>> to well know academic crypto conference publications that consider
>>> cryptanalysis of the alg in question, e.g. from crypto, or eurocrypt
>>> etc. One good rule of thumb here is that if there are no such
>>> references then you really should not register the thing.
>>
>> Good idea.
>>
>>> - 8.3: Is 65537 considered a "low" e?  "Low" is too vague there.
>>
>> No, it's not "low", but I can't back that up with a reference off the top of my
>> head.  Working group, what are the relevant documents here that we could
>> reference for this information?
>>
>>> - 8.5: I'd prefer there was no none. The WG did discuss it though, so
>>> I'll hold my nose.
>>
>> Understood.
>>
>>> - 8.6: suggesting a CA as a cure for oversized keys is odd, I think
>>> those are separable things and e.g. TOFU might be just as or more
>>> effective then X.509 here.
>>
>> Sean Turner suggested adding that text on July 6, 2012.  Proposed edits would
>> be welcomed.
>>
>>> - Appendix A:  Thanks for that! It'll save folks a lot of time. Might
>>> be better presented as a set of records and not as a fixed width table.
>>
>> You're welcome!
>>
>> I'll plan to work with the RFC Editor to figure out how to best present it and how
>> to achieve that.  I agree that the presentation is screwed up right now.
>>
>>> - I think most of the secdir stuff has been handled (and thanks for
>>> that) so I'm fine that the authors and AD are on top of that.
>>
>> Thanks again for your review and your participation in the working group.
>>
>> 				-- Mike
>>
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