From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.emacs.gnus.general/45368 Path: main.gmane.org!not-for-mail From: Simon Josefsson Newsgroups: gmane.emacs.gnus.general Subject: Re: [ANNOUNCE] contrib/hashcash.el spam fighter Date: Mon, 24 Jun 2002 14:06:54 +0200 (CEST) Sender: owner-ding@hpc.uh.edu Message-ID: References: NNTP-Posting-Host: localhost.gmane.org Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Trace: main.gmane.org 1024920470 17491 127.0.0.1 (24 Jun 2002 12:07:50 GMT) X-Complaints-To: usenet@main.gmane.org NNTP-Posting-Date: Mon, 24 Jun 2002 12:07:50 +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 17MSdJ-0004Xy-00 for ; Mon, 24 Jun 2002 14:07:50 +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 17MScj-00050d-00; Mon, 24 Jun 2002 07:07:13 -0500 Original-Received: by sina.hpc.uh.edu (TLB v0.09a (1.20 tibbs 1996/10/09 22:03:07)); Mon, 24 Jun 2002 07:07:33 -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 HAA20499 for ; Mon, 24 Jun 2002 07:07:23 -0500 (CDT) Original-Received: (qmail 457 invoked by alias); 24 Jun 2002 12:06:58 -0000 Original-Received: (qmail 452 invoked from network); 24 Jun 2002 12:06:57 -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; 24 Jun 2002 12:06:57 -0000 Original-Received: from yxa.extundo.com (localhost.localdomain [127.0.0.1]) by yxa.extundo.com (8.12.4/8.12.4) with ESMTP id g5OC6tlf029756; Mon, 24 Jun 2002 14:06:55 +0200 Original-Received: from localhost (jas@localhost) by yxa.extundo.com (8.12.4/8.12.1/Submit) with ESMTP id g5OC6sJd029753; Mon, 24 Jun 2002 14:06:55 +0200 X-Authentication-Warning: yxa.extundo.com: jas owned process doing -bs Original-To: Stainless Steel Rat In-Reply-To: Precedence: list X-Majordomo: 1.94.jlt7 Xref: main.gmane.org gmane.emacs.gnus.general:45368 X-Report-Spam: http://spam.gmane.org/gmane.emacs.gnus.general:45368 On Sun, 23 Jun 2002, Stainless Steel Rat wrote: > * Simon Josefsson on Sun, 23 Jun 2002 > | Pregenerated or not, the computation of the field requires someone to > | burn CPU time, if the limit is set sufficiently high spammers will > | find it costs too much to send spam, which is the point. > > For the sake of argument, say that hashcash.el users want a 128 bit hash. That's probably impractical for most people, even a ~30 bit collision can take about 10 minutes to find on a PC. > Today I calculate a 128 bit hash and send out a million messages using that > hash in the X-Hashcash header. Tomorow I generate a new 128 bit hash so > that the old one is no longer useful as filter bait, and send out another > million messages. I repeat this cycle indefinitely. This is not how X-Hashcash works. The sender must generate a X-Hashcash specific for each recipient. The recipient keeps a database of received coins to prevent double spendings. There are some descriptions and links at http://www.cypherspace.org/~adam/hashcash/. > Please explain to me where in this scheme I am burning any significant CPU > time generating hashes, or how it forces the spammer to do more work than > the recipients, because I cannot see it. The sender must burn CPU or the receiver will not accept the message, for some user defined value of "accept".