Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753130AbXLDTNU (ORCPT ); Tue, 4 Dec 2007 14:13:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751903AbXLDTNA (ORCPT ); Tue, 4 Dec 2007 14:13:00 -0500 Received: from main.gmane.org ([80.91.229.2]:36015 "EHLO ciao.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751816AbXLDTNA (ORCPT ); Tue, 4 Dec 2007 14:13:00 -0500 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: Russ Dill Subject: Re: Why does reading from /dev/urandom deplete entropy so much? Date: Tue, 4 Dec 2007 18:49:40 +0000 (UTC) Message-ID: References: <20071204114125.GA17310@torres.zugschlus.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: main.gmane.org User-Agent: Loom/3.14 (http://gmane.org/) X-Loom-IP: 63.226.32.16 (Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.10) Gecko/20071115 Firefox/2.0.0.10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 908 Lines: 17 Marc Haber zugschlus.de> writes: > > While debugging Exim4's GnuTLS interface, I recently found out that > reading from /dev/urandom depletes entropy as much as reading from > /dev/random would. This has somehow surprised me since I have always > believed that /dev/urandom has lower quality entropy than /dev/random, > but lots of it. > > This also means that I can "sabotage" applications reading from > /dev/random just by continuously reading from /dev/urandom, even not > meaning to do any harm. An application either needs to be cryptographically secure, or it doesn't. If it doesn't, then just use /dev/urandom to seed a PRNG. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/