Re: Entropy sources (was: /dev/random - a new approach)

[Sandy Harris]

On Thu, Aug 25, 2016 at 5:30 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:

> The network stack is a good source of entropy, *once it is online*.
> However, the most serious case is while the machine is still booting,
> when the network will not have enabled yet.
>
>         -hpa

One possible solution is at:
https://github.com/sandy-harris/maxwell

A small (< 700 lines) daemon that gets entropy from timer imprecision
and variations in time for arithmetic (cache misses, interrupts, etc.)
and pumps it into /dev/random. Make it the first userspace program
started and all should be covered. Directory above includes a PDF doc
with detailed rationale and some discussion of alternate solutions.

Of course if you are dealing with a system-on-a-chip or low-end
embedded CPU & the timer is really inadequate, this will not work
well. Conceivably well enough, but we could not know that without
detailed analysis for each chip in question.