From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.emacs.gnus.general/45386 Path: main.gmane.org!not-for-mail From: Simon Josefsson Newsgroups: gmane.emacs.gnus.general Subject: Re: [ANNOUNCE] contrib/hashcash.el spam fighter Date: Tue, 25 Jun 2002 10:56:44 +0200 Sender: owner-ding@hpc.uh.edu Message-ID: References: <02Jun24.115740edt.119250@gateway.intersystems.com> <02Jun24.151839edt.119751@gateway.intersystems.com> NNTP-Posting-Host: localhost.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: main.gmane.org 1024995479 27355 127.0.0.1 (25 Jun 2002 08:57:59 GMT) X-Complaints-To: usenet@main.gmane.org NNTP-Posting-Date: Tue, 25 Jun 2002 08:57:59 +0000 (UTC) Cc: "(ding)" Return-path: Original-Received: from malifon.math.uh.edu ([129.7.128.13]) by main.gmane.org with esmtp (Exim 3.33 #1 (Debian)) id 17Mm99-000776-00 for ; Tue, 25 Jun 2002 10:57:59 +0200 Original-Received: from sina.hpc.uh.edu ([129.7.128.10] ident=lists) by malifon.math.uh.edu with esmtp (Exim 3.20 #1) id 17Mm8I-0000DI-00; Tue, 25 Jun 2002 03:57:06 -0500 Original-Received: by sina.hpc.uh.edu (TLB v0.09a (1.20 tibbs 1996/10/09 22:03:07)); Tue, 25 Jun 2002 03:57:25 -0500 (CDT) Original-Received: from sclp3.sclp.com (qmailr@sclp3.sclp.com [209.196.61.66]) by sina.hpc.uh.edu (8.9.3/8.9.3) with SMTP id DAA22639 for ; Tue, 25 Jun 2002 03:57:13 -0500 (CDT) Original-Received: (qmail 13036 invoked by alias); 25 Jun 2002 08:56:48 -0000 Original-Received: (qmail 13024 invoked from network); 25 Jun 2002 08:56:46 -0000 Original-Received: from 178.230.13.217.in-addr.dgcsystems.net (HELO yxa.extundo.com) (217.13.230.178) by gnus.org with SMTP; 25 Jun 2002 08:56:46 -0000 Original-Received: from latte (yxa.extundo.com [217.13.230.178]) (authenticated bits=0) by yxa.extundo.com (8.12.4/8.12.4) with ESMTP id g5P8uhlf005428; Tue, 25 Jun 2002 10:56:43 +0200 Original-To: Stainless Steel Rat Mail-Copies-To: nobody X-Hashcash: 020625:ratinox@peorth.gweep.net:44812e7777225b6d X-Hashcash: 020625:ding@gnus.org:f0809c5ec095ab11 In-Reply-To: (Stainless Steel Rat's message of "Mon, 24 Jun 2002 22:15:03 -0400") Original-Lines: 27 User-Agent: Gnus/5.090007 (Oort Gnus v0.07) Emacs/21.3.50 (i686-pc-linux-gnu) Precedence: list X-Majordomo: 1.94.jlt7 Xref: main.gmane.org gmane.emacs.gnus.general:45386 X-Report-Spam: http://spam.gmane.org/gmane.emacs.gnus.general:45386 Stainless Steel Rat writes: > X-Hashcash is intended for sending mail to big mail-to-news gateways, > mailing list, and such. Not only, it works in peer 2 peer as well. Frankly, hashcash has some problems in big mailing lists (do you mint the coin to the mailing list or to each member? The latter probably requires the mailserver to do it, which is impractical, the former require some additional intelligence in clients (it knows which email lists it is a member of)). > It requires that the recipient -- the gateway or list -- publish a > challenge phrase and number of collisions bits that are required for > sending messages through it. These published challenges take the > place of the randomly generated numbers -- session keys -- that MTA > hashcash uses. > > The system is not so useful for end users simply because many (most?) have > no means of publishing challenges or informing legitimate senders that they > even exist. The whole thing falls apart if recipients cannot challenge > senders. hashcash.el uses the recipients email address as a challenge. If you know the recipients email address, you know the hashcash challenge, so this should work. A spammer could compute these, but he could only use it once.