[Cryptography-dev] OpenSSL Random Engine PR

[Laurens Van Houtven]

On Mon, Jan 20, 2014 at 11:04 PM, Glyph Lefkowitz
<glyph at twistedmatrix.com>wrote:

> FreeBSD and OS X use Yarrow, and Windows uses Fortuna, so nobody but Linux
> even has an exhaustible / blocking random "real actual for real entropy"
> API.  You can still exhaust the seed pool but as far as I know it would be
> literally impossible to tell (like, mathematically provably impossible by
> the properties of the various CSPRNGs used) that you had done so.
>
On Linux, /dev/random might still block sometimes, so you can tell that way
> as a regular user, and your applications might get stuck.
>
> At least, as far as I know.  The usual caveats about me not being a
> cryptographer, or actually knowing really anything about anything at all,
> apply.
>
> -glyph
>
>
I'm familiar with the CSPRNGs in modern OSes; I just thought we were
talking about exhausting the entropy of the CSPRNGs (so, say, urandom on
Linux and (u)random on FreeBSD and CryptGenRandom on Windows). IIUC, none
of the systems in play here actually use /dev/random in steady state (just
for key generation maybe). If the grandparent indeed meant /dev/random vs
/dev/urandom on Linux that would explain why, yes :-)

(FYI, I've yet to hear a cryptographer whose opinion on the blocking
/dev/random because better entropy in Linux isn't that it's pretty much
hogwash. djb is convinced they should just give up trying and implement
Fortuna or Yarrow already.)

cheers
lvh
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