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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
Date: Fri, 07 Jan 2005 20:26:21 +0100	[thread overview]
Message-ID: <87sm5d6nxe.fsf@deneb.enyo.de> (raw)
In-Reply-To: <20050107190536.GA14205@mtholyoke.edu> (Ron Peterson's message of "Fri, 7 Jan 2005 14:05:36 -0500")

* 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.)

  parent reply	other threads:[~2005-01-07 19:30 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-01-07 19:05 /dev/random vs. /dev/urandom Ron Peterson
2005-01-07 19:16 ` Paulo Marques
2005-01-07 19:24 ` Chris Friesen
2005-01-07 19:26 ` Florian Weimer [this message]
2005-01-07 19:27 ` linux-os
2005-01-07 19:40 ` Robert Love
2005-01-07 20:50   ` Ron Peterson
2005-01-07 21:39 ` Andries Brouwer
2005-01-07 22:39   ` linux-os
2005-01-07 17:55     ` Michal Schmidt
2005-01-07 23:29     ` Andries Brouwer
2005-01-08 17:34     ` Patrick J. LoPresti
2005-01-10 12:41       ` linux-os
2005-01-10 13:03         ` Paulo Marques
2005-01-10 14:39           ` Felipe Alfaro Solana
2005-01-10 15:13         ` Patrick J. LoPresti
2005-01-10 19:24         ` David Schwartz
2005-01-11 14:38         ` Andrea Arcangeli

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