Re: Opportunistic signatures - a proposed design

>> now, if i'm the sysadmin for a large bank, and my customers are 
>> targeted for phishing scams, then i'd be smart to use larger keys 
>> (among other obvious and non-obvious precautions).  If you're owned, 
>> you are owned.
>
> I have a friend who closely tied to an anti-phishing group.  He has 
> seen camram and thinks it could be very useful for anti-phishing 
> especially if we can get the signature stuff straightened out.  It's 
> useful from two perspectives.  First from the stamp reducing the 
> volume of phisher traffic getting through the second is from the 
> signatures being verifiable.  But the whole concept of verifiable 
> signatures gets into a very different discussion outside of 
> hashcash/camram.

What the bank really wants is not a signature, but a certificate, at 
least by my terminology.

A signature allows you to recognise a person reliably, but it only 
works if you've talked to that person before.  PGP uses signatures in a 
recursive manner to build a "web of trust".  Banks use signatures of 
various kinds (eg. handwritten, PIN) to allow their customers to 
authenticate themselves after opening an account.

A certificate assures you of who a stranger is, or rather that they 
have satisfied the issuing authority of their identity.  The IBM SCCC 
uses certificates, as does SSL.  Banks will ask customers for a 
certificate of identity, such as a passport, when they open an account. 
  Once the certificate has been associated with a signature, the 
signature carries similar weight to the certificate - but not before.

>> as an end user, do i benefit more from hashcash or signatures? i 
>> ~think~ hashcash is, overall, better. as a bank whose customers are 
>> targeted in phishing scams, do i benefit more from hashcash or 
>> signatures? i can protect myself much better if a PKI allowed 
>> customers to quickly identify if an email is *really* from me... 
>> domain-keys and SPF will both help with the problem of forgeries.
>
> hashcash is an introducer.  Opportunistic signatures allow for 
> efficient distribution of mail to people who agreed to know each other 
> (individuals and mailing lists).

Yes indeed.

> you can never really know if e-mail is "really" from you.  They're too 
> many ways for the identity process to be corrupted even if you meet 
> the person face-to-face with appropriate documentation.  You have no 
> of knowing it's truly accurate.  You need to understand where false 
> information can be injected into the system and if you can corrupt 
> human processes long before you ever go digital, then there is no 
> hope.  All you can do is trust people based on repeated exposure.

And this is why the PGP folks have their heads up their arses, to use a 
colloquialism.  There are so many other gaps in the system that there 
really is no point in forcing people who don't actually need it to use 
a "perfect" but hugely overcomplex system.

To abuse an analogy, this is like an airliner with a dodgy engine, a 
drunk First Officer, cracks in the rudder, and a malfunctioning 
starboard aileron, returning to the gate...  because there weren't 
enough "refreshing towelettes".

--------------------------------------------------------------
from:     Jonathan "Chromatix" Morton
mail:     [email protected]
website:  http://www.chromatix.uklinux.net/
tagline:  The key to knowledge is not to rely on people to teach you it.