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RE: Shared Public Knowledge

From: <michael.mccormick@wellsfargo.com>
Date: Fri, 13 Apr 2007 22:41:47 -0500
Message-ID: <8A794A6D6932D146B2949441ECFC9D6802B4D398@msgswbmnmsp17.wellsfargo.com>
To: <Mary_Ellen_Zurko@notesdev.ibm.com>
Cc: <public-wsc-wg@w3.org>
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.
 
Mike

  _____  

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. 

          Mez

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




<michael.mccormick@wellsfargo.com> 

04/12/2007 07:34 PM

To
<Mary_Ellen_Zurko@notesdev.ibm.com> 
cc
<public-wsc-wg@w3.org> 
Subject
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:

http://www.w3.org/2006/WSC/wiki/SharedPublicKnowledge


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 :-).

         Mez

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



<michael.mccormick@wellsfargo.com>
Sent by: public-wsc-wg-request@w3.org 

04/11/2007 07:47 PM



To
<public-wsc-wg@w3.org> 
cc
Subject
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 consumer. 

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 … 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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“THESE OPINIONS ARE STRICTLY MY OWN AND NOT NECESSARILY THOSE OF WELLS FARGO"
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Received on Saturday, 14 April 2007 03:42:07 GMT

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