[cap-talk] Firefox breaks the principle of identifiability

[Karp, Alan H]

Ben Laurie wrote:
> 
> Let's say I start with actually visiting my bank, and getting the 
> fingerprint of their cert. I then tediously type that into my 
> machine. 
> Now I can go to the bank's website, and find their trustable link to 
> PayPal. So, I go to PayPal and transfer some money from my 
> bank into my 
> PayPal account. I want to buy something with that money, so I follow 
> PayPal's trustable link to eBay. On eBay, I find Joe Sixpack 
> selling the 
> something, so I follow eBay's trustable link to Joe Sixpack. 
> Joe Sixpack 
> has a friend, Evil Bastard, and a trustable link to him on 
> his website. 
> Now I have a trustable link to Evil Bastard (who Joe Sixpack 
> described 
> as escrow.com) I give my money to Evil Bastard, who promptly 
> disappears, 
> as does Joe Sixpack.
> 
Then I've overinterpreted the meaning of "trust" in "trustable link".  A
trustable link is only saying "this link refers to the party I call X".
It's up to me to decide how much I trust X based on information from the
introducer and how much I trust the introducer.  In the case of my bank
introducing me to PayPal, I'm likely to assign a reasonable degree of
trust.  First of all, PayPal is widely known not to cheat people.
Second, my bank stands to lose my business if it introduces me to a
phony PayPal.  I'd probably make a similar assumptions about PayPal's
introducing me to eBay, although perhaps with less assurance, since my
business relationship with PayPal isn't as strong as with my bank.  I
can trust eBay's introduction of Joe Sixpack only to the extent that
eBay is willing to stand behind it.  In this case, that's the limit of
the insurance eBay provides.  I have no basis to rely on any
introductions provided by Joe Sixpack.  Doing so is just foolish.

________________________
Alan Karp
Principal Scientist
Virus Safe Computing Initiative
Hewlett-Packard Laboratories
1501 Page Mill Road
Palo Alto, CA 94304
(650) 857-3967, fax (650) 857-7029
https://ecardfile.com/id/Alan_Karp
http://www.hpl.hp.com/personal/Alan_Karp
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