From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.emacs.gnus.general/45339 Path: main.gmane.org!not-for-mail From: Simon Josefsson Newsgroups: gmane.emacs.gnus.general Subject: [ANNOUNCE] contrib/hashcash.el spam fighter Date: Sat, 22 Jun 2002 14:55:51 +0200 Sender: owner-ding@hpc.uh.edu Message-ID: NNTP-Posting-Host: localhost.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: main.gmane.org 1024750669 9086 127.0.0.1 (22 Jun 2002 12:57:49 GMT) X-Complaints-To: usenet@main.gmane.org NNTP-Posting-Date: Sat, 22 Jun 2002 12:57:49 +0000 (UTC) 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 17LkSb-0002MR-00 for ; Sat, 22 Jun 2002 14:57:49 +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 17LkR2-0005M7-00; Sat, 22 Jun 2002 07:56:12 -0500 Original-Received: by sina.hpc.uh.edu (TLB v0.09a (1.20 tibbs 1996/10/09 22:03:07)); Sat, 22 Jun 2002 07:56:32 -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 HAA16729 for ; Sat, 22 Jun 2002 07:56:22 -0500 (CDT) Original-Received: (qmail 24319 invoked by alias); 22 Jun 2002 12:55:57 -0000 Original-Received: (qmail 24314 invoked from network); 22 Jun 2002 12:55:56 -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; 22 Jun 2002 12:55:56 -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 g5MCtnlf002343 for ; Sat, 22 Jun 2002 14:55:53 +0200 Original-To: ding@gnus.org X-Hashcode: 020622:ding@gnus.org:e7f94f982c50cefd Original-Lines: 50 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:45339 X-Report-Spam: http://spam.gmane.org/gmane.emacs.gnus.general:45339 Pay Hashcash ============ A novel technique to fight spam is to require senders to do something costly for each message they send. This has the obvious drawback that you cannot rely on that everyone uses this technique, since it is optional, but it may be useful in smaller communities. The "something costly" is to burn CPU time, more specifically to compute a hash collision up to a certain number of bits. The resulting hashcash cookie is inserted in a `X-Hashcash:' header. For more details, and for the external application `hashcash' you need to install to use this feature, see `http://www.cypherspace.org/~adam/hashcash/'. Even more information can be found at `http://www.camram.org/'. If you wish to call hashcash for each message you send, say something like: (require 'hashcash) (add-hook 'message-send-hook 'mail-add-payment) The `hashcash.el' library can be found at `http://users.actrix.gen.nz/mycroft/hashcash.el', or in the Gnus development contrib directory. You will need to set up some additional variables as well: `hashcash-default-payment' This variable indicates the default number of bits the hash collision should consist of. By default this is 0, meaning nothing will be done. Suggested useful values include 17 to 29. `hashcash-payment-alist' Some receivers may require you to spend burn more CPU time than the default. This variable contains a list of `(ADDR AMOUNT)' cells, where ADDR is the receiver (email address or newsgroup) and AMOUNT is the number of bits in the collision that is needed. It can also contain `(ADDR STRING AMOUNT)' cells, where the STRING is the string to use (normally the email address or newsgroup name is used). `hashcash' Where the `hashcash' binary is installed. Currently there is no built in functionality in Gnus to verify hashcash cookies, it is expected that this is performed by your hand customized mail filtering scripts. Improvements in this area would be a useful contribution, however.