ad hoc IPsec or similiar

Paul Hoffman paul.hoffman at
Fri Jun 22 13:43:16 EDT 2007

At 11:52 PM +0800 6/22/07, Sandy Harris wrote:
>On 6/22/07, Eugen Leitl <eugen at> wrote:
>>So what's the state in ad hoc IPsec/VPN setup for any end points?
>The Linux FreeS/WAN project was working on "opportunistic encryption".
>The general idea is that if you use keys in DNS to authenticate gateways
>and IPsec for secure tunnels then any two machines can communicate
>securely without their administrators needing to talk to each other or to
>set up specific pre-arranged tunnels.
>There is an RFC based on that work:
>The FreeS/WAN project has ended. I do no know if the follow-on projects,
> and, support OE.

Note that that RFC is Informational only. There were a bunch of 
perceived issues with it, although I think they were more purity 
disagreements than anything.

FWIW, if you do *not* care about man-in-the-middle attacks (called 
active attacks in RFC 4322), the solution is much, much simpler than 
what is given in RFC 4322: everyone on the Internet agrees on a 
single pre-shared secret and uses it. You lose any authentication 
from IPsec, but if all you want is an encrypted tunnel that you will 
authenticate all or parts of later, you don't need RFC 4322.

This was discussed many times, and always rejected as "not good 
enough" by the purists. Then the IETF created the BTNS Working Group 
which is spending huge amounts of time getting close to purity again.

--Paul Hoffman, Director
--VPN Consortium

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