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

[Stainless Steel Rat <ratinox@peorth.gweep.net>]

* "Patrick J. LoPresti" <patl@curl.com>  on Fri, 28 Jun 2002
| The hashed value includes both the recipient's address and the date.
| The hash is valid only if the recipient address is correct *and* the
| date is recent.  "Recent" can be 28 days, 1 week, 1 day, or whatever
| you like; it depends on how long you want to allow the coin to be
| valid (for the convenience of the sender) versus how long you want to
| keep old coins listed in your local database.

Okay.  That can be problematic if you set it to be too long or too short.
It would really suck to have important, legitimate mail tagged as spam
because of sending delays.

| The sender must include a separate hash for every recipient, whether
| CC'd or BCC'd.

But how can you, the recipient, know which hash in a BCC hash list is
"yours" if there is no disclosure of the recipients list?  You can't.  But
like trying to abuse POP as an IMAP server, if you have a problem trying to
use a saw to drive nails then the problem is you, not the saw.  If you try
to use X-Hashcash as an authentication mechanism then you deserve what you
get.


| It does not matter if two duplicated coins appear somewhere in the
| world; what matters is whether somebody can exploit them.  With any
| reasonable number of bits, they cannot.  One false positive out of a
| million messages, or a billion messages, is certainly a ratio I could
| tolerate.

What about one false positive out of 100 messages?  Can you say "denial of
service"?  X-Hashcash does not scale.

| I do not think hashcash will catch on because it is too complex. 

Hashcash and X-Hashcash are not the same thing.  Please do not confuse the
two.

| But it is technically sound, your half-dozen misinformed messages on the
| topic notwithstanding :-).

Oh, I am hardly misinformed -now-.  I see X-Hashcash for what it is, what
it is intended to accomplish, and what some might try to misuse it as.

-- 
Rat <ratinox@peorth.gweep.net>    \ Ingredients of Happy Fun Ball include an
Minion of Nathan - Nathan says Hi! \ unknown glowing substance which fell to
PGP Key: at a key server near you!  \ Earth, presumably from outer space.
       That and five bucks will get you a small coffee at Starbucks.