re good read: Please do not change your password

[Dave Farber <dfarber () me com>]

Begin forwarded message:

> From: Benjamin Kuipers <kuipers () umich edu>
> Date: April 17, 2010 12:01:11 PM EDT
> To: dave () farber net
> Cc: ip <ip () v2 listbox com>, "Jonathan S. Shapiro" <shap () eros-os org>, Benjamin Kuipers <kuipers () umich edu>
> Subject: Re: [IP] good read: Please do not change your password

> Jonathan Shapiro makes a good point about the limitations of Herley's argument, but his own example about insurance 
> contains a similar limitation.
>
> Insurance is a rational investment because the *utility* functions of the individual insurance-purchasers are 
> different from the utility function of the insurance company that aggregates the risk.  For an individual, the 
> negative utility of a loss increases non-linearly with the dollar cost.  The insurance company has a large enough 
> asset base and risk pool so its utility function can increase linearly with cost.  The disparity of the two utility 
> functions makes the insurance deal (in principle) a good deal from both sides.
>
> That is, if I get seriously injured or ill, medical bills in the millions could bankrupt me and my family, while 
> paying a few thousand a year for insurance will not make a qualitative difference to my life (though the quantitative 
> difference might still be annoying).
>
> Carrying this back to password security, Gene Spafford's point is relevant.  The small but annoying cost of 
> continually changing passwords does not actually provide the coverage one might believe, since the risks have changed.
>
> It's like paying those insurance premiums, and then discovering when it's too late that the insurance company won't 
> cover your loss.
>
> Ben Kuipers
>
>
> At 2:15 PM -0400 4/16/10, Dave Farber wrote:
> > Begin forwarded message:
> > > From: "Jonathan S. Shapiro" <shap () eros-os org>
> > > Date: April 16, 2010 12:27:18 PM EDT
> > > To: dave () farber net
> >
> > > Subject: Re: [IP] good read: Please do not change your password
> >
> > > ...
> >
> > >  
> >
> > > Under Herley's argument, rational actors should also dispense with home insurance, life insurance, and automobile 
> > > insurance. Indeed we should dispense with *any* insurance. Insurance policies do not insure in areas where they 
> > > will lose money. Therefore, if insurance exists, the expected cost to the buyer is higher than the expected loss.
> >
> > >  
> >
> > > ...
> >
> > >  
> >
> > >  
> >
> > > Jonthan Shapiro
>
> > Archives  
>
>
> -- 
> Benjamin Kuipers, Professor         email:  kuipers () umich edu
> Computer Science and Engineering    tel:    1-734-647-6887
> University of Michigan              fax:    1-734-763-1260
> 2260 Hayward Street                 http://eecs.umich.edu/~kuipers
> Ann Arbor, Michigan 48109 USA



-------------------------------------------
Archives: https://www.listbox.com/member/archive/247/=now
RSS Feed: https://www.listbox.com/member/archive/rss/247/
Powered by Listbox: http://www.listbox.com