Return-path: Received: from sabertooth01.qualcomm.com ([65.197.215.72]:40283 "EHLO sabertooth01.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753061AbbGaIji convert rfc822-to-8bit (ORCPT ); Fri, 31 Jul 2015 04:39:38 -0400 From: "Pan, Miaoqing" To: Kalle Valo , Stephan Mueller , "Sepehrdad, Pouyan" , "Jacobson, David" CC: Oleksij Rempel , "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 Date: Fri, 31 Jul 2015 08:39:35 +0000 Message-ID: <3ec13417acdc48628adaedb68d259b9c@NASANEXM01E.na.qualcomm.com> (sfid-20150731_104346_949074_DF9D0D46) References: <1436946847-10909-1-git-send-email-miaoqing@qca.qualcomm.com> <55B60BC9.8040800@rempel-privat.de> <3945775.m5HblJPgiO@tauon.atsec.com> <8738043ith.fsf@kamboji.qca.qualcomm.com> In-Reply-To: <8738043ith.fsf@kamboji.qca.qualcomm.com> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: +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 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