Re: [dhcwg] on use case discussion for draft-ietf-dhc-sedhcpv6

[Ted Lemon <[e-mail]>]

On Feb 25, 2015, at 2:09 PM, 神明達哉 <[e-mail]> wrote:
> In that sense I'd still love to see an answer to my specific question:
> http://www.ietf.org/mail-archive/web/dhcwg/current/msg16268.html
> (aside from whether to include that answer in the final document).

Here's the question:

> It's still vague to me...specifically what kind of attack should we
> worry about in the case of client->server authentication when we use
> the shared secret mechanism, and in which sense is it more serious
> than with the public/private key mechanism?

What we are trying to do with the public key is to identify a client and authenticate the client's identity.   If you want to phrase it in terms of preventing an attack, the attack it prevents is one client presenting another client's identity and getting access to the second client's resources because the credential it presents is never authenticated.

But in practice, as a general rule we simply don't ever bother to treat clients as having meaningful identities, because there is no way to authenticate them.   So we aren't trying to prevent an attack, really.   We are trying to provide an enabling technology that allows the network infrastructure to do something new, that it couldn't previously do.