[Python-Dev] writing to /dev/*random [was: BDFL ruling request: should we block ...]

Stephen J. Turnbull stephen at xemacs.org
Sat Jun 11 20:16:44 EDT 2016

This is related to David Mertz's request for backward compatible
initialization, not to the bdfl decision.

Steven D'Aprano writes:

 > I don't think that's something which the Python interpreter ought to do 
 > for you, but you can write to /dev/urandom or /dev/random (both keep 
 > their own, separate, entropy pools):
 > open("/dev/urandom", "w").write("hello world")

This fails for unprivileged users on Mac.  I'm not sure what happens
on Linux; it appears to succeed, but the result wasn't what I

Also, when entropy gets low, it's not clear how additional entropy is
allocated between the /dev/random and /dev/urandom pools.

 > But of course there's the question of where you're going to get a
 > source of noise to write to the file. While it's (probably?) 
 > harmless to write a hard-coded string to it, I don't think its
 > going to give you much entropy.

Use a Raspberry-Pi, or other advanced expensive<wink/> hardware.
There's no real excuse for not having a hardware generator if the Pi
has one!  I would guess you can probably get something with a USB
interface for $20 or so.

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