From: Florian Weimer <fw@deneb.enyo.de>
To: Ron Peterson <rpeterso@mtholyoke.edu>
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
Content-Length: 823
Lines: 20

* 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.)
-
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/