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List:       linux-wireless
Subject:    RE: [PATCH 2/2] ath9k: export HW random number generator
From:       "Pan, Miaoqing" <miaoqing () qti ! qualcomm ! com>
Date:       2015-07-31 8:39:35
Message-ID: 3ec13417acdc48628adaedb68d259b9c () NASANEXM01E ! na ! qualcomm ! com
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+Pouyan & David.

-----Original Message-----
From: Kalle Valo [mailto:kvalo@codeaurora.org] 
Sent: Friday, July 31, 2015 3:09 PM
To: Stephan Mueller
Cc: Oleksij Rempel; Pan, Miaoqing; linville@tuxdriver.com; \
linux-wireless@vger.kernel.org; Theodore Ts'o; linux-crypto@vger.kernel.org; \
                nhorman@tuxdriver.com
Subject: Re: [PATCH 2/2] ath9k: export HW random number generator

Stephan Mueller <smueller@chronox.de> writes:

> > -rw-rw-r-- 1 lex lex 2564096 Jul 27 11:36 hwrng.out
> > -rw-rw-r-- 1 lex lex 2468394 Jul 27 11:36 hwrng.out.bz2
> > 
> > Do i understand it correctly, in case of hwrng bzip was able to find 
> > enough pattern to compressed the data? Even with format overhead?
> > 
> > I'm no an expert, help of an expert would be welcome, added some more 
> > people to CC
> 
> This one does not look good for a claim that the RNG produces white 
> noise. An RNG that is wired up to /dev/hwrng should produce white 
> noise. Either by having an appropriate noise source or by conditioning 
> the output of the noise source.
> 
> When conditioning the output, you have to be careful about the entropy claim. 
> For example, you cannot state that the data stream from your noise 
> source has close to one bit of entropy for each obtained bit. Thus, 
> the conditioner must ensure that the data from the noise source is 
> collected and its entropy is maintained and accumulated.
> 
> However, the hwrandom framework does not provide any conditioning 
> logic. And I would say that such conditioner logic should not reside 
> in a driver either. I would say that the discussed RNG does not seem 
> fit for hooking it up with the hwrandom framework.

Based on the discussion I'm going to revert this patch, at least for now.

--
Kalle Valo
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