From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261558AbVAGTaD (ORCPT ); Fri, 7 Jan 2005 14:30:03 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261551AbVAGT2m (ORCPT ); Fri, 7 Jan 2005 14:28:42 -0500 Received: from mail.enyo.de ([212.9.189.167]:14055 "EHLO mail.enyo.de") by vger.kernel.org with ESMTP id S261545AbVAGT00 (ORCPT ); Fri, 7 Jan 2005 14:26:26 -0500 From: Florian Weimer To: Ron Peterson Cc: linux-kernel@vger.kernel.org Subject: Re: /dev/random vs. /dev/urandom References: <20050107190536.GA14205@mtholyoke.edu> Date: Fri, 07 Jan 2005 20:26:21 +0100 In-Reply-To: <20050107190536.GA14205@mtholyoke.edu> (Ron Peterson's message of "Fri, 7 Jan 2005 14:05:36 -0500") Message-ID: <87sm5d6nxe.fsf@deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Ron Peterson: > When I compile and run the code below, the string of octal characters > generated by reading /dev/random contains long strings of zeroes. I was > under the impression that /dev/random is "more random" than > /dev/urandom, and will block when it runs out of entropy until it > gathers more. It's only when RAND_LEN is on the largish side that these > strings of zeroes appear. > read( fd, dat, RAND_LEN ); This is the bug. *Always* check the return value of read. (Try running your program with "strace -e read" for a hint of what's really going on.)