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

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 expected.

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 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. http://scruss.com/blog/2013/06/07/well-that-was-unexpected-the-raspberry-pis-hardware-random-number-generator/

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