Subject: [Hipsec] DH Group selection

From: [email-masked] (Kristian Slavov)
Date: Tue Dec 2 06:15:01 2003

Hi,

The latest draft, draft-moskowitz-hip-08, lists 8 DH groups. Are all these 
groups required to be implemented, or just optional?
If optional, how do we signal the responder that we do not support certain DH 
group? Do the other implementations support all 8 groups?

-- 
Kristian Slavov
Research Assistant
Helsinki Institute for Information Technology
Gsm: +358-40-7220960

---

From: [email-masked] (Julien Laganier)
Date: Tue Dec 2 09:20:01 2003

Kristian Slavov wrote:
> Hi,
> 
> The latest draft, draft-moskowitz-hip-08, lists 8 DH groups. Are all 
> these groups required to be implemented, or just optional?

Dunno...

> If optional, how do we signal the responder that we do not support 
> certain DH group? Do the other implementations support all 8 groups?

My implementation support 8 groups.

If some DH groups are optionnal, perhaps the initiator needs to signal 
what DH groups it supports before receiving a DH from the responder. It 
means that the signalisation should be done in I1. Hence, since I1 isn't 
protected at all, this signal might be subject to a bidding down attack, 
by choosing 768 bits, right?

So I don't know what to do with that. One solution might be to make 
group 1, 2, 3 and 4 (up to 2048 bits) mandatory so that the responder 
can freely choose a security level up to 2048 bits. When it'd be 
required to have more than 2048 bits, we can increment the HIP version 
number and make others DH groups mandatory...

Thoughts?

Thanks,

--julien

---

From: [email-masked] (Robert Moskowitz)
Date: Tue Dec 2 12:44:00 2003

I am getting ready for a meeting, but IIRC, the DH group is selected in R1 
and I2.

the Responder supplies what it will play with and the initiator selects 
what it can deal with.

At 06:23 AM 12/2/2003, Julien Laganier wrote:
>So I don't know what to do with that. One solution might be to make group 
>1, 2, 3 and 4 (up to 2048 bits) mandatory so that the responder can freely 
>choose a security level up to 2048 bits. When it'd be required to have 
>more than 2048 bits, we can increment the HIP version number and make 
>others DH groups mandatory...
>
>Thoughts?
>
>Thanks,
>
>--julien
>
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