[ntp:questions] Re: using ntpd to feed the system's random device

Adrian von Bidder grazdan at fortytwo.ch
Sat Sep 24 11:12:33 UTC 2005


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Clinging to sanity, Folkert van Heusden mumbled in his beard:

> On some systems, there's a kernel random-device. That device collects
> entropy from numerous devices (like interrupts from disk i/o, keyboard
> clicks intervals, etc.). Now as it seems that the drift and the
> offsets can be pretty much random I was wondering it ntpd could be
> enhanced so that it sends this data to the kernel random-device? It
> can be helpfull for systems that, for example, hardly have any
> disk-i/o and such.

Should work - network delays are very random, so using the lower few
bits of the unprocessed offsets (raw, each time ntpd receives a packet)
would probably give you some random input.

Problems:
 - ntp is very low traffic, so you'd not get much random data
 - kernel/userspace interface - so far, afaik, most random sources for
kernel random device is kernel-internal.
 - ntp is time-critical code, you'd have to take care not to make the
timekeeping worse by this processing.

So I guess, primarily because of the first item, that it's not worh it
if you're not extremely starved of random data.

- -- vbi


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