From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Andreas Schwab Newsgroups: gmane.emacs.bugs Subject: bug#13949: fill-paragraph is buggy, but using MD5 is even more buggy Date: Mon, 28 Mar 2016 12:32:26 +0200 Message-ID: <87r3euhozp.fsf@linux-m68k.org> References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1459161205 16875 80.91.229.3 (28 Mar 2016 10:33:25 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 28 Mar 2016 10:33:25 +0000 (UTC) Cc: 13949@debbugs.gnu.org To: "Petros Travioli" Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Mon Mar 28 12:33:14 2016 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1akUTv-0005Vl-CM for geb-bug-gnu-emacs@m.gmane.org; Mon, 28 Mar 2016 12:33:11 +0200 Original-Received: from localhost ([::1]:40104 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akUTu-0004bv-7R for geb-bug-gnu-emacs@m.gmane.org; Mon, 28 Mar 2016 06:33:10 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:46443) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akUTr-0004bX-0w for bug-gnu-emacs@gnu.org; Mon, 28 Mar 2016 06:33:07 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1akUTm-0008Ud-0c for bug-gnu-emacs@gnu.org; Mon, 28 Mar 2016 06:33:06 -0400 Original-Received: from debbugs.gnu.org ([208.118.235.43]:43687) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akUTl-0008UZ-Tt for bug-gnu-emacs@gnu.org; Mon, 28 Mar 2016 06:33:01 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1akUTl-00084P-Mq for bug-gnu-emacs@gnu.org; Mon, 28 Mar 2016 06:33:01 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Andreas Schwab Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Mon, 28 Mar 2016 10:33:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 13949 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 13949-submit@debbugs.gnu.org id=B13949.145916115130983 (code B ref 13949); Mon, 28 Mar 2016 10:33:01 +0000 Original-Received: (at 13949) by debbugs.gnu.org; 28 Mar 2016 10:32:31 +0000 Original-Received: from localhost ([127.0.0.1]:40814 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1akUTH-00083f-8y for submit@debbugs.gnu.org; Mon, 28 Mar 2016 06:32:31 -0400 Original-Received: from mail-out.m-online.net ([212.18.0.10]:39249) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1akUTE-00083W-MA for 13949@debbugs.gnu.org; Mon, 28 Mar 2016 06:32:29 -0400 Original-Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 3qYVbH5BYwz3hjYx; Mon, 28 Mar 2016 12:32:27 +0200 (CEST) Original-Received: from localhost (dynscan1.mnet-online.de [192.168.6.68]) by mail.m-online.net (Postfix) with ESMTP id 3qYVbH2zqzzvdWQ; Mon, 28 Mar 2016 12:32:27 +0200 (CEST) X-Virus-Scanned: amavisd-new at mnet-online.de Original-Received: from mail.mnet-online.de ([192.168.8.182]) by localhost (dynscan1.mail.m-online.net [192.168.6.68]) (amavisd-new, port 10024) with ESMTP id 0pwLGoPhd1L9; Mon, 28 Mar 2016 12:32:26 +0200 (CEST) X-Auth-Info: n1DkNj5xS2R/zYhqS0gAV2c4Q1YFm9cy6IBS0U+KxnoV2K+SyIhT+XTHzhSyLXv4 Original-Received: from igel.home (ppp-88-217-16-153.dynamic.mnet-online.de [88.217.16.153]) by mail.mnet-online.de (Postfix) with ESMTPA; Mon, 28 Mar 2016 12:32:26 +0200 (CEST) Original-Received: by igel.home (Postfix, from userid 1000) id 4135F2C3E2B; Mon, 28 Mar 2016 12:32:26 +0200 (CEST) X-Yow: Look into my eyes and try to forget that you have a Macy's charge card! In-Reply-To: (Petros Travioli's message of "Mon, 28 Mar 2016 06:55:58 +0200") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.92 (gnu/linux) X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 208.118.235.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.bugs:115628 Archived-At: "Petros Travioli" writes: > But that's exactly what happens when you are using hash functions to > verify buffer equality, just with a more complicated mathematical > formulation and at a slightly different scale. > > So don't use hash functions to a two-sided correct answer to test buffer > equality. For a one-sided answer (if hash(x) != hash(y) then x != y), you > are fine. There is a difference between a hash function and a cryptographic hash function. An inportant property of a cryptographic hash function is the avalanche effect, that means a small change in the plaintext will result in a big change in the hash value. That makes such a hash function suitable for the reverse condition x != y => hash(x) != hash(y), with a very high probability of being true. Andreas. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different."