This is the mail archive of the
ecos-discuss@sourceware.org
mailing list for the eCos project.
RE: Re: Entropy gathering?
- From: Jay Foster <jay at systech dot com>
- To: 'Grant Edwards' <grante at visi dot com>, ecos-discuss at sources dot redhat dot com
- Date: Thu, 3 Apr 2008 11:27:06 -0800
- Subject: RE: [ECOS] Re: Entropy gathering?
A colleague implemented something like this by creating a function that
could be called from various places at random times, such as the ethernet
driver (ether_input()), serial port modem signal changes, etc. The function
would read the HAL microsecond clock value and write the lower 16-bits to
/dev/random. After a pre-determined number of such events, this function
would stop writing to /dev/random and simply return.
Jay
-----Original Message-----
From: Grant Edwards [mailto:grante@visi.com]
Sent: Thursday, April 03, 2008 12:18 PM
To: ecos-discuss@sources.redhat.com
Subject: [ECOS] Re: Entropy gathering?
On 2008-04-03, Grant Edwards <grante@visi.com> wrote:
> The BSD stacks appear to use an aRC4 keystream for "random"
> data. The stream uses a constant seed and then mixes in the
> system clock value. It could be worse, but it's not great
> either.
Upon reading the above statement, I think I should clarify that
the "system time" that's mixed in is the HAL's hardware counter
value and not the system tick count time. The hardware counter
is changing much faster (a good thing), but it provides
relatively few bits (on my targets, it ranges from 14-18).
--
Grant Edwards grante Yow! My mind is making
at ashtrays in Dayton ...
visi.com
--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss