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RE: Shared Public Knowledge

From: Timothy Hahn <hahnt@us.ibm.com>
Date: Wed, 18 Apr 2007 02:08:33 -0400
To: public-wsc-wg@w3.org
Message-ID: <OF74B8828C.9D935F4C-ON852572C1.0019981A-852572C1.0021BE12@us.ibm.com>

Your example below reminded me of the method that Experian, TransUnion, 
and Equifax use to help them understand that the person they expect to be 
talking to them to get their free credit report is who they think they 
are.  All of them, by my recollection, put up a question asking to answer 
something about one of your accounts before displaying your credit report. 
 The questions change, as do the accounts about which the questions are 
asked.  But the answers given do lend some credence to the site since they 
had to have that information in order for them to present it to the 
requester as a possible answer.

Tim Hahn
IBM Distinguished Engineer

Internet: hahnt@us.ibm.com
Internal: Timothy Hahn/Durham/IBM@IBMUS
phone: 919.224.1565     tie-line: 8/687.1565
fax: 919.224.2530

Sent by: public-wsc-wg-request@w3.org
04/13/07 11:41 PM

RE: Shared Public Knowledge

SiteKey (actually RSA Passmark) is just one of many commercial products 
that use user-selected images and/or passphrases to authenticate site to 
user.  However that's not really SPK in my opinion since the user's choice 
of image / phrase does constitute a shared secret.
I agree true KBA / OOWA is generally about user authentication, however 
there's a subtle (perceived) site-to-user authentication that also occurs 
as a by-product.  If a site asks me a multiple choice question "What model 
car do you drive? (a) 1977 Ford Pinto, (b) 2004 Ford Mustang, (c) 2007 
Toyota Prius, (d) 1981 AMC Pacer" this has a strong psychological effect. 
Seeing that the site obviously knows what car I drive (it's "b" by the way 
:) reassures me this site must be the legitimate one that I have a prior 
relationship with.  If the site knew something even more personal about me 
(e.g., monthly mortgage payment) it would be even more reassuring.  I know 
it's an irrational response, but in this arena perception trumps reality.

From: Mary Ellen Zurko [mailto:Mary_Ellen_Zurko@notesdev.ibm.com] 
Sent: Friday, April 13, 2007 4:53 PM
To: McCormick, Mike
Cc: public-wsc-wg@w3.org
Subject: RE: Shared Public Knowledge

I disagree, and if it makes sense as a site to user antipattern (and I 
sense the jury still out on that), if there is concensus, we can say 
something appropriate about what, if anything, should be implied for the 
other direction (and the going in position from me would be, nothing 
should be implied for the other direction). 

What things other than SiteKey use information (secret, public, or shared 
public) to (attempt to) authenticate the site to the use? Anyone have more 
examples? Thanks Chuck for the Sitekey one. And Chuck, is the last login 
time _really_ meant to authenticate the site to the user? I thought it was 
to give the user a hint if the account had been unknowingly used by 
someone else. 


Mary Ellen Zurko, STSM, IBM Lotus CTO Office       (t/l 333-6389)
Lotus/WPLC Security Strategy and Patent Innovation Architect

04/12/2007 07:34 PM

RE: Shared Public Knowledge

Thanks for this clarification.  But my concern is if W3C declares SPK 
based site-to-user authentication to be an anti pattern, that certainly 
implies it should never be used in the other direction either.

From: Mary Ellen Zurko [mailto:Mary_Ellen_Zurko@notesdev.ibm.com] 
Sent: Thursday, April 12, 2007 3:17 PM
To: McCormick, Mike
Cc: public-wsc-wg@w3.org
Subject: Re: Shared Public Knowledge

I would like to do a rewind on this thread. Everyone who participated, go 
back to the proposed recommendation that we discussed:


It's about authenticating the server to the user (since that's one of our 
primary goals). Not the user to the server. 

So I will assume all discussion of the latter was interesting and 
informative (it was for me), but not about the actual proposal being 
discussed. Maybe that's because the proposal is about something nobody 
does or wants to do. That would make it nice and safe for our 
recommendations :-).


Mary Ellen Zurko, STSM, IBM Lotus CTO Office       (t/l 333-6389)
Lotus/WPLC Security Strategy and Patent Innovation Architect

Sent by: public-wsc-wg-request@w3.org 
04/11/2007 07:47 PM


Shared Public Knowledge

I had to drop off the line for a few minutes at the top of the hour during 
this morning's meeting.  Regrettably that moment came during the Lightning 
Discussions just as Chuck Wade was responding to MEZ's presentation on 
Shared Public Knowledge (SPK).  By the time I rejoined to discussion had 
moved on to the next topic. 
What I would have said given the opportunity is that Chuck is 100% right. 
In our industry this battle has been fought many times and I see little 
good coming from taking a hard line against all online use of SPK. 
Many US companies rely on services provided by the likes of Choicepoint & 
Acxiom to perform Knowledge Based Authentication (KBA) or Out of Wallet 
Authentication (OOWA) of consumers in certain situations, especially in 
cases where no prior business relationship exists between the FI and said 
These KBA systems typically ask a series of randomly chosen multiple 
choice questions designed to score a user's knowledge of semi-private 
information about himself or herself.  Examples might include "What model 
car do you drive"? or "What¡¦s the amount of your monthly mortgage 
payment?".  A determined criminal could undeniably obtain this information 
from public sources, perhaps even use it to impersonate others, but that 
doesn't mean there is no legitimate use case for KBA. 
A blanket prohibition against KBA is unnecessary and would never be 
accepted.  Asking the user enough SPK based questions is not an 
unreasonable authentication technique as long as the associated risk is 
low, or when SPK is only being used to supplement some other credential 
for extra assurance. 
The much maligned Mother's Maiden Name is an example of weak KBA ¡K but 
much stronger ones are possible using the enormous databases of personal 
data that are available from brokers today.  So I think the SPK 
"anti-pattern" would benefit from being softened a bit to acknowledge 
there's a place for it under certain conditions. 
Thanks, Mike 
Michael McCormick,CISSP
Lead Architect, Information Security Technology 
Wells Fargo Bank 
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MAC N9301-01J 
Minneapolis MN 55479 
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Received on Wednesday, 18 April 2007 06:08:43 UTC

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