Re: [Uta] updated I-Ds

Hi Orit,

Each choice we make needs a rationale, for sure.

The question of where to put it (per paragraph, in a separate section, 
in a separate document) is mostly editorial. For us, having the 
rationale close to the decision is helpful. For the presumed audience 
(system architects, implementers) it's best if the rationale is 
separate, so that the essence of the document is as short as possible.

Thanks,
	Yaron

On 02/26/2014 02:11 PM, Orit Levin (LCA) wrote:
> How about documenting this kind of applicability considerations under a short "Rationale" paragraph for each choice?
> That would be especially helpful for hard choices where there is a no clear winner
> - in terms of implementation availability and/or
> - it is determined by a deployment case
>
> Orit.
>
>> -----Original Message-----
>> From: Uta [mailto:uta-bounces@ietf.org] On Behalf Of Yaron Sheffer
>> Sent: Wednesday, February 26, 2014 12:43 AM
>> To: Stephen Farrell; Daniel Kahn Gillmor; Watson Ladd
>> Cc: uta@ietf.org
>> Subject: Re: [Uta] updated I-Ds
>>
>> The document recommends ECDHE over DHE, because DHE parameters
>> cannot be
>> negotiated and so some people will be stuck with DH-1024. See
>> http://tools.ietf.org/id/draft-sheffer-tls-bcp-02.html#rfc.section.4.2
>>
>> But for those people who cannot switch to ECDHE, the tradeoff is exactly
>> between RSA-2048 and DH-1024. Stephen would recommend DH-1024 in this
>> case, because the NSA can get at the server's private key and then, if
>> you don't have PFS, you're hosed.
>>
>> I would recommend RSA-2048 in this case, because DH-1024 can be broken
>> today with commercially available compute power (buy a few Amazon extra
>> large instances and let them run for a few months). Also, and this is a
>> value judgment, I think the cryptographic break is a higher risk than
>> wholesale theft of the private keys.
>>
>> Thanks,
>> 	Yaron
>>
>> On 02/26/2014 12:40 AM, Stephen Farrell wrote:
>>> -----BEGIN PGP SIGNED MESSAGE-----
>>> Hash: SHA1
>>>
>>>
>>>
>>> On 02/25/2014 09:42 PM, Daniel Kahn Gillmor wrote:
>>>> Yes, agreed.  DHE-1024 needs to be deprecated.
>>>>
>>>
>>> True. But I would hope UTA WG BCPs can be broadly
>>> implemented without waiting for a massive upgrade
>>> so its possible we could have to live with DH-1024.
>>>
>>> Much better if that's only a niche or just gets fixed,
>>> but that's the kind of trade off that needs to be
>>> considered. And an important part of that trade off
>>> is not between DH-1024 and RSA-2048, but rather
>>> between PFS and non-PFS ciphersuites.
>>>
>>> S.
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>>>
>>>
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>> O7
>>>
>> viQ1M3iTdNHmaROxdT+qAtt6OXK6eY20bG/QHFvZrUX+RW051LhbCh3WvztX
>> yjfH
>>>
>> BOI+VypROebsmDODi/bFU8JnP4BI8m0F9nsDQTv7QXqV+kG7Rf6nmX7Dru0n
>> 0/ad
>>>
>> uTi1WAeTaFft7gKJMGp1enA9ruTP6BqfmcGG+6ejzS9D5bFNQjndTpmsLTLqK
>> CVU
>>>
>> XfO+DRd2F0t/SQVOgTGilxD31gDGlvJioNA4IXjd3PMi6+1BSFuLj10z+SaaTHCe
>>>
>> +yjOVcz8Dg6HaY6PZwW+9o9UDS6Y8f/pnOMxSqy7D8I3sKwuyMJ/cHwM/ksS
>> tz4=
>>> =6IKl
>>> -----END PGP SIGNATURE-----
>>>
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