[sudo-discuss] Art Murmur discussion list sign up page

[William Budington]

On 06/11/2013 06:32 PM, GtwoG PublicOhOne wrote:
> There is a way to stop spam dead in its tracks, which is to charge a
> teeny-tiny fee for every outgoing email.  This would destroy the
> economics / business model that allows spam to thrive on "free" email. 
> (As Richard Stallman says, "free speech isn't the same thing as free
> beer.")  However that won't help if scumbags break into networks and
> steal user accounts. 

Back in 1997, Adam Back came up with a similar concept.  Instead of
making sending spam financially expensive, make it computationally
expensive.  He proposed a system whereby the email would have to compute
a hash with certain characteristics in order to be valid.  He called
this a Proof of Work, because your machine had to work to generate a
valid hash that the receiving server could verify instantaneously.
Generating such a hash for an individual email is relatively easy, but
you'd have to generate it for each email you want to send.  This quickly
becomes computationally (and thus financially) expensive, when you want
to generate thousands of emails at once.

Eventually his Proof-of-Work system became the key element of the
Bitcoin currency.

The reason why it didn't take off back then is that it's not just the
spammers who are sending bulk emails.  With mailing lists, every email
you send is multiplied by the number of people on the list.  So those
costs add up pretty quickly, even for people who aren't sending out
malicious traffic.

Bill