Payments as an answer to spam

[Arnold G. Reinhold]

At 9:45 AM -0400 5/13/03, Ian Grigg wrote:
>...
>
>As a footnote from economics, it is considered
>a bad thing to create a monetary system that
>bases its scarcity on destruction of assets.
>Such schemes are expected to be dominated by
>schemes that achieve the same effect but
>manage to conserve their assets.
>
>This applies to hashcash (c.f. Adam B.) or
>those various hash collision schemes of
>tokenising money (c.f. Ron R?).

In the paper world, it is quite common to do apparently wasteful 
things in the hope of getting your message read. Examples include 
fancy stationary, hand addressed envelopes, using FedEx where a 37 
cent stamp would suffice, and paying Ed McMahon for the use of his 
picture on envelopes. I think hashcash should be seen in that light.

If hashcash proof of work is combined with an easy to use whitelist, 
the hash stamp is only needed when communicating with strangers. For 
most people that happens infrequently, so quite high work levels are 
reasonable, even one minute per message  or more.  If a bidding war 
develops, individual users with gigaHerz machines will be able to 
outbid the spammers and I think users will accept the delays 
necessary. I could see a service that sampled email and suggested 
what hashcash level is required to stand out above most spammers.

Handheld devices would be at a disadvantage, but wireless email 
providers could offer a stamping service. Also there is more 
acceptance of a per message charge in the wireless world (e.g. SMS) 
so an alternative would be for the wireless carrier to sign messages 
attesting to the amount that the sender has paid. The PKI and 
private-key security issues in doing this are quite manageable, 
unlike in schemes requiring all individuals to sign messages.  This 
could easily be combined with a proof of payment to charity approach.

E-mail clients that can support a variety of approaches, whitelists, 
hashcash, proof of payment, rule-based filters, etc., may be the best 
answer to spam.

Arnold  Reinhold



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