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Re: Last ditch proposal for crypto suites
In message <p05111a0eb993fe9b9f62@[165.227.249.18]>, Paul Hoffman / VPNC writes
:
>At 11:44 AM -0400 8/29/02, Steven M. Bellovin wrote:
>>You know my opinion -- scrap a la carte. But let me ask the question
>>differently: Paul Hoffman, in your interoperability tests do you see
>>many different combinations actually used? Or don't your tests go
>>there?
>
>We see a huge amount of variation. Of the systems that have GUIs, I have seen
>- default of DES and MD5
>- default of DES and SHA-1
>- default of TripleDES and SHA-1
>- no options: always does TripleDES and SHA-1
>and probably some others I have forgotten.
>
>Note that some of these systems have GUIs that only allow single
>choices for the administrator, but send out multiple proposals anyway
>("in order to increase interoperability", I am told).
>
>Almost every system allows different settings for Phase 1 and Phase
>2, and on the ones I tinkered with, none warned if you used DES in
>Phase 1 and TripleDES in Phase 2.
>
>Based on this and the agony I hear from users, I'm a strong proponent
>of suites.
If I understand you correctly, you're saying that implementors and/or
administrators are making different choices on what combinations to
offer, thus hurting interoperability? That suggests that even if we
stick with a la carte, we should specify which combinations MUST be
offered, from among the standard algorithms (subject to administrator
security override, of course).
Aside -- and donning my AD hat for a moment -- I've become increasing
concerned about interoperability. We need to ensure that our
standards, as well as being technical correct and secure, specify
a minimum set of mandatory-to-implement mechanisms that will always be
there. Specs that say "you can solve this problem by doing (a) or (b)"
are not acceptable, since different vendors will make different choices.
Empirically, we didn't get this right in IPsec. Let's fix that now --
and precisely how we fix it, with suites or with better specification
of how a la carte choices should be assembled, is less important from
that perspective.
--Steve Bellovin, http://www.research.att.com/~smb (me)
http://www.wilyhacker.com ("Firewalls" book)