Return-path: Received: from smtp.codeaurora.org ([198.145.29.96]:40363 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750789AbbGaHIu (ORCPT ); Fri, 31 Jul 2015 03:08:50 -0400 From: Kalle Valo 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 References: <1436946847-10909-1-git-send-email-miaoqing@qca.qualcomm.com> <55B60BC9.8040800@rempel-privat.de> <3945775.m5HblJPgiO@tauon.atsec.com> Date: Fri, 31 Jul 2015 10:08:42 +0300 In-Reply-To: <3945775.m5HblJPgiO@tauon.atsec.com> (Stephan Mueller's message of "Mon, 27 Jul 2015 13:01:46 +0200") Message-ID: <8738043ith.fsf@kamboji.qca.qualcomm.com> (sfid-20150731_090854_707497_D3431C8B) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-wireless-owner@vger.kernel.org List-ID: 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