Subject: Kerberos Digital Signatures ?

From: Tim Alsop <[email-masked]>
Date: Wed, 18 Jun 2003 19:19:46 +0100

Hi,

Does anybody know if any IETF work has been done yet to use a KDC to store a fixed (unique for each principal) private key that could be made available to a program on a Kerberos Client system after authentication. The idea being that this private key could be used for digital signature purposes. Obviously to verify the signature a corresponding public key would need to be published somewhere ? 

Any thoughts or ideas are welcome ?

Thanks, 

Tim.

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From: "Matt Crawford" <[email-masked]>
Date: Wed, 18 Jun 2003 14:37:25 -0500

> Does anybody know if any IETF work has been done yet to use a KDC
> to store a fixed (unique for each principal) private key that could
> be made available to a program on a Kerberos Client system after
> authentication. The idea being that this private key could be used
> for digital signature purposes. Obviously to verify the signature a
> corresponding public key would need to be published somewhere ?

I never heard of anything like that. Several sites, including mine,
provide a roughly similar service which probably isn't exactly what
you want: A user holding a TGT can run "kx509" which generates a
keypair and submits the public key to a KCA server (Kerberized CA) in
a Kerberos-authenticated transaction. The KCA creates and signs a
certificate for that public key and that authenticated user.  (In our
case it looks up the user's full name from a W2K AD.)

Clearly this might not be useful for long-term signatures, since the
private key is rather ephemeral.  But you could create an analogous
service that generate digital signatures, creating and holding a
private key on the first request.

---

From: Edward Flick <[email-masked]>
Date: Wed, 18 Jun 2003 13:15:02 -0700 (PDT)

Couldn't you just store the public/private keys in a Kerberized LDAP server.  Making the private key only readable to the authenticated identity?  Just a thought.

Tim Alsop <[email-masked]> wrote:
Hi, 

Thanks, 

Tim. 

Edward Flick
Enterprise Applications Designer / Database Administrator / Web Administrator
CDF, Inc.

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From: "Matt Crawford" <[email-masked]>
Date: Wed, 18 Jun 2003 15:55:07 -0500

> Couldn't you just store the public/private keys in a Kerberized
> LDAP server. Making the private key only readable to the
> authenticated identity? Just a thought.

Possible, I suppose, but part of our requirements is that the private
key not live more than a day or so.  And many other people require
that private keys never be moved over the network.  (Although when it
comes down to it, that's unenforceable.)

---

From: Derek Atkins <[email-masked]>
Date: 19 Jun 2003 11:48:02 -0400

It sounds like what you want is either Sphinx (Kerberos with temporary
RSA keys instead of DES keys, created (and patented) by DEC around
1990) or perhaps UMich's Junk Keys (www.citi.umich.edu) where they
generate a "junk" key certificate for the user to use during an
authentication session.

-derek

-- 
       Derek Atkins                 617-623-3745
       [email-masked]             www.ihtfp.com
       Computer and Internet Security Consultant