Subject: RE: Proxy PKI. Was: IBM alternative to PKI?

From: Trevor Perrin <[email-masked]>
Date: Fri, 17 May 2002 11:45:42 -0700

Hi Stephen,

To seek clarification: I was suggesting the use of an "online", but not
necessarily "inline", intermediary.  Ie, the communication might not flow
through the intermediary, the client would just perform a request/response
protocol with him to produce a signed statement, say.  Is "link" or
"hop-to-hop" the appropriate term for that?  

Regardless, my use of "end-to-end" was confusing and I'll avoid it in
future.  Thanks,

Trevor

-----Original Message-----
From: Stephen Kent [mailto:[email-masked]]
Sent: Friday, May 17, 2002 11:32 AM
To: Trevor Perrin
Cc: [email-masked]
Subject: RE: Proxy PKI. Was: IBM alternative to PKI?

At 11:14 AM -0700 5/17/02, Trevor Perrin wrote:
>Hi Lynn,
>
>I agree that using a password<->PKI middleman doesn't provide end-to-end
PKI
>trust.  But it could provide end-to-end trust, in the sense that, when the
>middleman signs, he explicitly mentions the name being signed for, or when
>something is encrypted to the middleman, it explicitly includes the name
the
>encrypted data is intended for.
>
>Such a middleman would be a replacement for an identity certificate/key
>pair, but it would not "artifically fabricate" signatures by holding
>multiple keys, one for each client, but would instead make honest
statements
>such as "I authenticated Alice with a password, and am signing this on her
>behalf".
>
>The point, I guess, is that you can have end-to-end security (meaning
>authenticated or confidential communications with end-users) without
>end-to-end PKI, if you trust the PKI endpoints to make authentic statements
>from, or deliver confidential statements to, end-users..

Trevor,

This is not how the phrase "end-to-end security" is used in the 
literature, and thus I would suggest one not use the phrase to refer 
to any scheme in which an intermediary in the communication path must 
be trusted to preserve the security services being advertised. Terms 
such as "link security" and "hop-by-hop security" have been used in 
the past to describe analogous schemes.

Steve

---

From: Stephen Kent <[email-masked]>
Date: Fri, 17 May 2002 14:59:30 -0400

Trevor,

Given the clarification above, this sort of scheme sounds more like a 
proxy authentication service, analogous to the many single signon 
techniques that have been developed, but applied here to signatures 
for NR purposes. Given the requirements imposed on signatures for NR 
purposes in many contexts, e.g., in the EU directive, it's not clear 
that any form of proxy would meet those requirements.

Steve