From: Stephan Mueller <smueller@chronox.de>
To: "Austin S. Hemmelgarn" <ahferroin7@gmail.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>, "David Jaša" <djasa@redhat.com>,
"Andi Kleen" <andi@firstfloor.org>,
sandyinchina@gmail.com,
"Jason Cooper" <cryptography@lakedaemon.net>,
"John Denker" <jsd@av8n.com>,
"H. Peter Anvin" <hpa@linux.intel.com>,
"Joe Perches" <joe@perches.com>, "Pavel Machek" <pavel@ucw.cz>,
"George Spelvin" <linux@horizon.com>,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 0/5] /dev/random - a new approach
Date: Mon, 20 Jun 2016 20:32:43 +0200 [thread overview]
Message-ID: <8999970.pstTbGZv5G@positron.chronox.de> (raw)
In-Reply-To: <f22f4cd6-8198-71a0-9b79-9f10070758f3@gmail.com>
Am Montag, 20. Juni 2016, 13:07:32 schrieb Austin S. Hemmelgarn:
Hi Austin,
> On 2016-06-18 12:31, Stephan Mueller wrote:
> > Am Samstag, 18. Juni 2016, 10:44:08 schrieb Theodore Ts'o:
> >
> > Hi Theodore,
> >
> >> At the end of the day, with these devices you really badly need a
> >> hardware RNG. We can't generate randomness out of thin air. The only
> >> thing you really can do requires user space help, which is to generate
> >> keys lazily, or as late as possible, so you can gather as much entropy
> >> as you can --- and to feed in measurements from the WiFi (RSSI
> >> measurements, MAC addresses seen, etc.) This won't help much if you
> >> have an FBI van parked outside your house trying to carry out a
> >> TEMPEST attack, but hopefully it provides some protection against a
> >> remote attacker who isn't try to carry out an on-premises attack.
> >
> > All my measurements on such small systems like MIPS or smaller/older ARMs
> > do not seem to support that statement :-)
>
> Was this on real hardware, or in a virtual machine/emulator? Because if
> it's not on real hardware, you're harvesting entropy from the host
> system, not the emulated one. While I haven't done this with MIPS or
> ARM systems, I've taken similar measurements on SPARC64, x86_64, and
> PPC64 systems comparing real hardware and emulated hardware, and the
> emulated hardware _always_ has higher entropy, even when running the
> emulator on an identical CPU to the one being emulated and using KVM
> acceleration and passing through all the devices possible.
>
> Even if you were testing on real hardware, I'm still rather dubious, as
> every single test I've ever done on any hardware (SPARC, PPC, x86, ARM,
> and even PA-RISC) indicates that you can't harvest entropy as
> effectively from a smaller CPU compared to a large one, and this effect
> is significantly more pronounced on RISC systems.
It was on real hardware. As part of my Jitter RNG project, I tested all major
CPUs from small to big -- see Appendix F [1]. For MIPS/ARM, see the trailing
part of the big table.
[1] http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.pdf
Ciao
Stephan
next prev parent reply other threads:[~2016-06-20 18:33 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-31 18:37 [PATCH v4 0/5] /dev/random - a new approach Stephan Mueller
2016-05-31 18:37 ` [PATCH v4 1/5] crypto: DRBG - externalize DRBG functions for LRNG Stephan Mueller
2016-05-31 18:38 ` [PATCH v4 2/5] random: conditionally compile code depending on LRNG Stephan Mueller
2016-05-31 18:39 ` [PATCH v4 3/5] crypto: Linux Random Number Generator Stephan Mueller
2016-05-31 18:39 ` [PATCH v4 4/5] crypto: LRNG - enable compile Stephan Mueller
2016-05-31 18:39 ` [PATCH v4 5/5] random: add interrupt callback to VMBus IRQ handler Stephan Mueller
2016-05-31 22:34 ` [PATCH v4 0/5] /dev/random - a new approach George Spelvin
2016-06-15 16:17 ` David Jaša
2016-06-15 16:58 ` Stephan Mueller
2016-06-17 13:56 ` David Jaša
2016-06-17 15:26 ` Sandy Harris
2016-06-18 8:22 ` Stephan Mueller
2016-06-18 8:21 ` Stephan Mueller
2016-06-18 14:44 ` Theodore Ts'o
2016-06-18 16:31 ` Stephan Mueller
2016-06-20 17:07 ` Austin S. Hemmelgarn
2016-06-20 18:32 ` Stephan Mueller [this message]
2016-06-21 13:05 ` Austin S. Hemmelgarn
2016-06-21 13:19 ` Tomas Mraz
2016-06-21 17:18 ` Austin S. Hemmelgarn
2016-06-21 17:23 ` Stephan Mueller
2016-06-21 17:54 ` Austin S. Hemmelgarn
2016-06-21 18:05 ` Stephan Mueller
2016-06-21 13:20 ` Stephan Mueller
2016-06-21 17:51 ` Austin S. Hemmelgarn
2016-06-21 18:04 ` Stephan Mueller
2016-06-21 19:31 ` Austin S. Hemmelgarn
2016-06-22 5:16 ` Stephan Mueller
2016-06-22 12:54 ` Austin S. Hemmelgarn
2016-06-22 13:25 ` Stephan Mueller
2016-06-21 13:42 ` Pavel Machek
2016-06-21 17:17 ` Austin S. Hemmelgarn
2016-06-21 12:25 ` David Jaša
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