Subject: [Syslog] fingerprint vs PSK

From: "Rainer Gerhards" <[email-masked]>
Date: Fri, 23 May 2008 08:44:04 +0200

Hi all,

in my implementation effort (now mostly completed), I asked several
people for advise on implementing fingerprints. In almost all cases the
initial reply was "why use non-standard fingerprints when we have PSK"?
I know that RFC 4279 in section 1.1 says:

   If the main goal is to avoid Public-Key Infrastructures (PKIs),
   another possibility worth considering is using self-signed
   certificates with public key fingerprints.  Instead of manually
   configuring a shared secret in, for instance, some configuration
   file, a fingerprint (hash) of the other party's public key (or
   certificate) could be placed there instead.

However, I think it would be useful to add some short text why
fingerprints are more desirable. And the real question is: are they
actually more desirable?

Rainer
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From: <[email-masked]>
Date: Fri, 23 May 2008 11:08:24 +0300

If you have one transport sender and one transport receiver, there's
probably no big difference (except that most TLS implementations,
at least in their official releases, don't support RFC 4279 yet).

If you have a large number of transport senders, things get different.
Especially if you're satisfied with authenticating only the server,
PSKs would mean more administrative work (when new clients are added),
since it has to be configured on both ends (while the server
fingerprint needs to be configured only on the new client -- and since
it's not secret, you can e.g. put it in your installation scripts or
instructions).

(That said, it's clear that fingerprints are not the *only* possible
solution here -- but I'd really like to pick one option that's 
good enough and get this document published, rather than spend 
lot of time analyzing all the possible solutions.)

Best regards,
Pasi

> -----Original Message-----
> From: ext Rainer Gerhards
> Sent: 23 May, 2008 09:44
> To: [email-masked]
> Subject: [Syslog] fingerprint vs PSK
> 
> Hi all,
>

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From: "Rainer Gerhards" <[email-masked]>
Date: Fri, 23 May 2008 10:16:38 +0200

Pasi,

inline...

> From: [email-masked] [mailto:[email-masked]]
> Sent: Friday, May 23, 2008 10:08 AM
> To: Rainer Gerhards; [email-masked]
> Subject: RE: [Syslog] fingerprint vs PSK
> 
> 

A very good point indeed.

> lot of time analyzing all the possible solutions.)

Thanks for the explanation. I agree to one good enough solution is fine.
I would suggest to add a few sentences on the reasoning to the ID.

Rainer

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From: "Moehrke, John (GE Healthcare)" <[email-masked]>
Date: Fri, 23 May 2008 07:22:21 -0400

Great question... No they are not... You can still use certificates
without needing an expensive PKI. Self-signed certificates managed
manually (trust). Rob and I keep trying to tell you this, and we have
provided white papers explaining scalability and management methods. I
recommend that you do NOT invent something special for syslog. Choose
certificates and be done.

John

> From: [email-masked] [mailto:[email-masked]] On
Behalf
> Of Rainer Gerhards
> Sent: Friday, May 23, 2008 1:44 AM
> To: [email-masked]

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From: Jon Callas <[email-masked]>
Date: Fri, 23 May 2008 09:27:18 -0700

> certificates and be done.

Let me agree and add that you can also set up your own private PKI,  
which I mean to be different in that you spin your own root and the  
root signs the other certs. That way, they're not self-signed -- they  
descend from a root, it's just your root.

	Jon