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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMuHMdX5-kSWVJ_QFXY+L2L6iY0Zo7GAL5uF-uPGJAXM=wZxgw@mail.gmail.com>
Date:	Thu, 12 Sep 2013 14:15:35 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Stephan Mueller <smueller@...onox.de>
Cc:	"Theodore Ts'o" <tytso@....edu>,
	LKML <linux-kernel@...r.kernel.org>, dave.taht@...ferbloat.net
Subject: Re: [PATCH] /dev/random: Insufficient of entropy on many architectures

On Thu, Sep 12, 2013 at 2:08 PM, Stephan Mueller <smueller@...onox.de> 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@...ux-m68k.org

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/