linux-kernel - Re: [PATCH] CPU Jitter RNG: inclusion into kernel crypto API and /dev/random

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]

Date:	Sat, 09 Nov 2013 23:04:07 +0100
From:	Clemens Ladisch <clemens@...isch.de>
To:	Stephan Mueller <smueller@...onox.de>
CC:	Nicholas Mc Guire <der.herr@...r.at>,
	Theodore Ts'o <tytso@....edu>, Pavel Machek <pavel@....cz>,
	sandy harris <sandyinchina@...il.com>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH] CPU Jitter RNG: inclusion into kernel crypto API and
 /dev/random

Stephan Mueller wrote:
> Am Donnerstag, 7. November 2013, 02:03:57 schrieb Nicholas Mc Guire:
>> On Wed, 06 Nov 2013, Stephan Mueller wrote:
>>> Besides, how on earth shall an attacker even gain knowledge about the
>>> state of the CPU or disable CPU mechanisms? Oh, I forgot, your NSA
>>> guy. But if he is able to do that, all discussions are moot because
>>> he simply disables any noise sources by flipping a bit, reads the
>>> memory that is used to hold the state of the RNG or just overwrites
>>> the memory locations where data is collected, because the general
>>> protection mechanisms offered by the kernel and the underlying
>>> hardware are broken.
>>
>> No need to gain knowledge of the internal CPU state itt would be
>> sufficient to be able to put the CPU in a sub-state-space in which
>> the distribution is shifted. it may be enough to reduce the truely
>> random bits of some key only by a few bits to make it suceptible to
>> brute force attacks.
>
> Note, the proposed RNG contains an unbias operation (the Von-Neumann
> unbiaser) which is proven to remove any bias when it is established that
> the individual observations are independent. And the way the
> observations are generated ensures that they are independent.

"Independent" does not mean that your own code avoids reusing data from
the previous loop iteration; it means that the _entire_ process that
generates the bits is not affected by any memory of the past.

The observations are derived from the internal CPU state, which is *not*
reset between measurements.


Regards,
Clemens
--
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/