A Trial Balloon to Ban Email?

[Bill Stewart]

At 04:43 PM 05/12/2003 -0700, bear wrote:
>On Mon, 12 May 2003, Bill Sommerfeld wrote:
> >So, what's my reason to accept a "payment in cpu time"?  As best as I
> >can tell, a "payment in cpu time" means that someone *else* doesn't
> >get a payment in cpu time with their spam.  I still get the spam.
> >It seems analagous to a protocol that proves that someone burned a
> >dollar bill.
> >
> >A scheme where I actually get something of value might have a bit more 
> traction..
>
>The question here is not about whether *you* get anything worth value;
>the question is whether the economics of email can be changed in such
>a way that spam is no longer profitable.

For *you* to get something of value, there needs to be a payment system,
and the sender needs to be willing to spend money to talk to you.
There are environments in which that holds, but they're mostly specialized.

Hashcash doesn't change the economics of spam as much by imposing a
direct cost on the sender (since the amortized cost of less than an
hour's CPU time is pretty low unless you're buying lots of it),
but by limiting the rate at which a single machine can send mail.

60 seconds of CPU time per message means 1440 messages/day/CPU,
as opposed to tens of thousands per hour, which limits the rate at which
suckers can be located and money extracted from them, e.g. the ex-spammer
on Slashdot the other day would be making $5/week instead of $1000/day.

Also, spammers have a problem that they get detected and shut down,
so slowing down the rate they can transmit decreases the number of messages
that they can send before they get shut down.

For large-volume senders, the cost is measurable -
a $100 CPU over 1 year is ~30 cents/day, or about 0.02 cents/message,
which is a higher than the current costs of spam,
but for people who aren't buying CPUs just to max them out on email,
the CPU amortization is mostly a sunk cost.





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