Subject: [anonsec] Why use self-signed certs at all?

From: Atul.Sharma at nokia.com ([email-masked])
Date: Mon Nov 22 07:25:38 2004

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On
> Behalf Of ext Stephen Kent
> Sent: Friday, November 19, 2004 5:23 PM
> To: Discussions of anonymous Internet security.
> Cc: [email-masked]
> Subject: RE: [anonsec] Why use self-signed certs at all?
> 
> 
> At 2:11 PM -0500 11/19/04, <[email-masked]> wrote:
> >I agree self signed certificates provide no more trust than
> >a secret and increase the complexity.
> 
> the comparison was not to a secret, but to an "open secret" which is 
> probably not secret at all.  of source, maybe we don't really know 
> what is meant by this latter term so ...

That is what I meant. What Paul Hoffman calls "shared (non)secret". The
statement shall still be true that self-signed certs do not provide 
any extra level of trust.

> >If the secrets have life-time then SAs can be reestablished during
> >its lifetime....same as during a cert's lifetime.
> 
> a cert has the advantage that it discloses no info that enables a 
> passive wiretapper to pose as the cert holder, during the time that 
> the public key from the cert is used to secure other keys, etc. 
> however, if one sends the open secret via IKE's encrypted SA, I guess 
> you can argue that it's not exposed to passive intercept, although it 
> is exposed to attacks that cause you to connect to the wrong 
> destination,

Your concerns on MITM and channel bindings are addressed in a separate
thread. I believe you agreed there:

	"I'm not saying one can't figure out a way to do this and still have 
	an evaluated crypto module, but it will require some care and maybe 
	changes to existing modules."

Could not "figuring out a way to do this" be an agenda item for BTNS?

> >Besides, I do not feel that a use of self-signed certs forces BTNS
> >into PKI4IPSEC realm. Self-signed certs is not PKI, so why force
> >BTNS into a PKI-specific work? It sounds bizarre to me.
> >
> >Atul
> 
> somewhat tongue in cheek, a self signed cert represents a 
> very small PKI :-)

Huh? PKI is Public Key Infrastructure. What part of self-signed cert is 
"Public"? Self-signed cert is more "lack-of-PKI". Just usage of any kind
of cert, does not imply PKI.

> Steve

Atul

---

From: kent at bbn.com (Stephen Kent)
Date: Mon Nov 22 08:44:38 2004

>any extra level of trust.

"trust" is not the issue here. we all agree that the credential being 
used is not a reliable source for an authenticated ID. the issue is 
what types of info we should use that will also allow us to achieve 
some of the other goals people have cited, e.g., resistance to MITM 
attacks.

>Could not "figuring out a way to do this" be an agenda item for BTNS?

It could be, or we could avoid the problem by choosing methods that 
do not give rise to this sort of concern.

>of cert, does not imply PKI.

In the phrase "public key infrastructure" the word "public" modifies 
"key" and thus your question is easy to answer, i.e., the public key 
in a self-signed cert is the public part. it's the infrastructure 
part that is trivial in this case. also, you should be aware of what 
the phrase "tongue in cheek" means in order to properly interpret my 
comment.

Steve