Re: [ANNOUNCE] contrib/hashcash.el spam fighter

["Patrick J. LoPresti" <patl@curl.com>]

Stainless Steel Rat <ratinox@peorth.gweep.net> writes:

> Real hashcash -- NOT X-Hashcash!!!! They are not the same thing! --
> does not force senders to spend hours and hours calculating a single
> hash collision.  The idea is to make him spend 5 or 6 seconds
> calculating a single collision.  That is negligible for most
> legitimate uses, but for spammers sending out bulk, that 5 seconds
> times 5 million is thousands of hours of CPU time.  That is where
> hashcash works... and X-Hashcash does not, so PLEASE! do not confuse
> the two or treat them as the same thing.

If those 5 million recipients all use X-Hashcash, the spammer has to
compute a distinct hash for each of them.  Sounds like it works to me.

X-Hashcash is just hashcash implemented by the end user.  You seem to
think that this is somehow fundamentally different than having the MTA
do it, but you have yet to give a very good argument why.  (Other than
failing to work with BCC, but I suspect many people would consider
that fairly minor.)  Having to keep a database of spent coins is the
only extra cost of a non-challenge-response implementation, but that
database is cheap.  Ever use nnmail-treat-duplicates?

If all you want to do is cost the sender 5 or 6 seconds at the MTA
level, why not just stall the TCP connection for 5 seconds per
envelope recipient?  It would be much simpler than hashcash :-).

 - Pat