From: "Theodore Ts'o" <tytso@mit.edu>
To: Stephan Mueller <smueller@chronox.de>
Cc: George Spelvin <linux@sciencehorizons.net>,
andi@firstfloor.org, cryptography@lakedaemon.net,
herbert@gondor.apana.org.au, hpa@linux.intel.com,
joe@perches.com, jsd@av8n.com, linux-crypto@vger.kernel.org,
linux-kernel@vger.kernel.org, linux@horizon.com, pavel@ucw.cz,
sandyinchina@gmail.com
Subject: Re: [PATCH v5 0/7] /dev/random - a new approach
Date: Tue, 21 Jun 2016 01:12:55 -0400 [thread overview]
Message-ID: <20160621051255.GG9848@thunk.org> (raw)
In-Reply-To: <10477997.AvJKPRy4pc@positron.chronox.de>
On Mon, Jun 20, 2016 at 09:00:49PM +0200, Stephan Mueller wrote:
>
> The time stamp maintenance is the exact cause for the correlation: one HID
> event triggers:
>
> - add_interrupt_randomness which takes high-res time stamp, Jiffies and some
> pointers
>
> - add_input_randomness which takes high-res time stamp, Jiffies and HID event
> value
>
> The same applies to disk events. My suggestion is to get rid of the double
> counting of time stamps for one event.
>
> And I guess I do not need to stress that correlation of data that is supposed
> to be entropic is not good :-)
What is your concern, specifically? If it is in the entropy
accounting, there is more entropy in HID event interrupts, so I don't
think adding the extra 1/64th bit of entropy is going to be problematic.
If it is that there are two timestamps that are closely correleated
being added into the pool, the add_interrupt_randomness() path is
going to mix that timestamp with the interrupt timings from 63 other
interrupts before it is mixed into the input pool, while the
add_input_randomness() mixes it directly into the pool. So if you
think there is a way this could be leveraged into attack, please give
specifics --- but I think we're on pretty solid ground here.
Cheers,
- Ted
next prev parent reply other threads:[~2016-06-21 5:14 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-19 15:58 [PATCH v5 0/7] /dev/random - a new approach Stephan Mueller
2016-06-19 15:59 ` [PATCH v5 1/7] crypto: DRBG - externalize DRBG functions for LRNG Stephan Mueller
2016-06-19 15:59 ` [PATCH v5 2/7] random: conditionally compile code depending on LRNG Stephan Mueller
2016-06-19 16:00 ` [PATCH v5 3/7] crypto: Linux Random Number Generator Stephan Mueller
2016-06-19 16:58 ` Andi Kleen
2016-06-19 18:31 ` Stephan Mueller
2016-06-19 16:00 ` [PATCH v5 4/7] crypto: LRNG - enable compile Stephan Mueller
2016-06-19 16:01 ` Stephan Mueller
2016-06-19 16:01 ` [PATCH v5 6/7] crypto: isolate the chacha20_block function Stephan Mueller
2016-06-19 16:04 ` [PATCH v5 7/7] crypto: LRNG - add ChaCha20 support Stephan Mueller
2016-06-19 19:36 ` [PATCH v5 0/7] /dev/random - a new approach Pavel Machek
2016-06-19 20:47 ` Sandy Harris
2016-06-20 5:51 ` Stephan Mueller
2016-06-20 8:27 ` Pavel Machek
2016-06-20 15:28 ` Theodore Ts'o
2016-06-20 15:43 ` Stephan Mueller
2016-06-20 18:44 ` George Spelvin
2016-06-20 19:00 ` Stephan Mueller
2016-06-21 5:12 ` Theodore Ts'o [this message]
2016-06-21 5:17 ` Stephan Mueller
2016-06-21 7:12 ` Nikos Mavrogiannopoulos
2016-06-21 7:32 ` Stephan Mueller
2016-06-21 16:03 ` Austin S. Hemmelgarn
2016-06-21 16:28 ` Stephan Mueller
2016-06-21 18:22 ` Austin S. Hemmelgarn
2016-06-21 18:46 ` Stephan Mueller
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