Re: [PATCH] /dev/random: Insufficient of entropy on many architectures

[Geert Uytterhoeven]

On Thu, Sep 12, 2013 at 2:08 PM, Stephan Mueller <smueller@xxxxxxxxxx> wrote:
>>BTW, I prefer a different name than "random_get_fast_cycles()", as it's
>>better to have something that returns different and unpredictable
>>numbers than an actual monotonic cycle counter.
>
> A monotonic counter is fully ok. Note, for /dev/random, the occurrence
> of events delivers entropy. Thus, we have to be able to precisely
> measure that occurrence. The timer itself does not need to deliver any
> entropy as long as it is fast.

Well, in my specific case (m68k/Amiga) I can use:
  - a 24-bit counter running at only ca. 15 or 31 kHz (actual
frequency may vary),
  - a 16-bit counter running at ca. 700 kHz.

That is, if they have to be monotonic cycle counters.

If not, I can mix the two (e.g. "a << 8 | (b & 0xff)") to get a 32-bit value.
That result would be fine for /dev/random, I guess, but it's not
really "get_cycles()".

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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