[Cryptography] Finding Entropy Isn't That Hard
kentborg at borg.org
Thu Sep 12 11:52:20 EDT 2013
On 09/12/2013 10:41 AM, Kent Borg wrote:
> routers and servers are not as bad off as people say.
Not that more sources is bad. A new trustworthy HW entropy source would
be good. Even a suspect rdrand is worth XORing in (as Linux does on the
machine I am using right now).
But if you thirst for more entropy keep looking in your current
hardware, server boxes are particularly good hunting grounds for a few
more dribs of entropy:
- current RPM of all the fans (the proverbial entropy-starved server
can have a lot of fans)
- disk ("SMART") statistics (temperatures and error counts, multiplied
by the number of disks)
These are all things that could wear out or go wrong, which means they
need monitoring because...you can't otherwise know what they are. Cool,
that's a decent definition of entropy. Sample them regularly and hash
them into your entropy pool. Not a lot of bandwidth there, but if your
RNG does a good job of hiding its internal state, and you are mixing in
a dozen more bits here and a dozen more bits there...pretty soon you
have made the attacker's job a lot harder.
Maybe not as sexy as a lavalamp or radioactive gizmos, but more
practical and available now.
More information about the cryptography