From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 733D8FF885D for ; Tue, 28 Apr 2026 12:33:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/1ATwxQzv3bF5ExhjGlAkFYLpgrDUAcbjVTMBpGbV2Y=; b=Q4EU844lUeAKQEWr0Fxf2RRa3K JVbaQGquXTuiAcH5J2KNCI1B8JBNWNsXGkzn6sKh+IXBlIGa7h5szTnYQYVDiW8CwIpIYNhUdUufI 4P4DBSj0zY55XxQ3JKi5o5sZ8Cp7YsAlUfRJdbgcAuphd1TyNCT5Z9dW4PSO+uRnTBkcJh/WAY/HZ UNsu6yiTc6uJBUCzfqlgot17L1F8VCl0kSphACWdL2SpIrgsecdVqjUXZyw34iqDHWvQTz/BRlfAD rq79kqDFM3zxmNVV9n+g1Z1n6IKO5KWW+VQ96VUYvl/D/xE8NUdLChgyRTqUFQiTrS2SS1pWSSce0 KkDsPLIA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wHhcg-00000001RLY-2WkO; Tue, 28 Apr 2026 12:33:06 +0000 Received: from out-170.mta0.migadu.com ([91.218.175.170]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wHhcd-00000001RKr-0ip7 for linux-arm-kernel@lists.infradead.org; Tue, 28 Apr 2026 12:33:05 +0000 Date: Tue, 28 Apr 2026 14:32:52 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1777379579; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/1ATwxQzv3bF5ExhjGlAkFYLpgrDUAcbjVTMBpGbV2Y=; b=LLgqsbCyD6VGWbuT5dDv3ZJJt1w6Dsy36SGj4v1eqG8CNz9mVhT4Z9b7+FBlAcQIAK6shv /4TeF5Pze9BNdIEFsVI8x2dvjNlEByTQvl9jduj0s4gb3vQ0pY9A82JP5+m8qrYhP6Se43 jt3xvAsewskiFyGJoFHu9Ejbux7IzeY= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Thorsten Blum To: Marek =?iso-8859-1?Q?Beh=FAn?= Cc: Bill Cox , Herbert Xu , "David S. Miller" , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Linus Walleij , Ard Biesheuvel , stable@vger.kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] crypto: atmel-sha204a - drop hwrng quality reduction for ATSHA204A Message-ID: References: <20260428101430.514838-3-thorsten.blum@linux.dev> <25ntssyy6t5uwxlwfpmrpzpcq6xv62l643hflf26hxi6lv5wqu@6vub6ysczjvd> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <25ntssyy6t5uwxlwfpmrpzpcq6xv62l643hflf26hxi6lv5wqu@6vub6ysczjvd> X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260428_053303_708688_0B7D1438 X-CRM114-Status: GOOD ( 22.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Marek, On Tue, Apr 28, 2026 at 01:18:08PM +0200, Marek Behún wrote: > Adding Bill Cox (waywardgeek) to the conversation. > > In the meantime Nack from me on this patch. > > From the original messages by Bill, it seems to me the part he was reviewing > was the ATSHA204A. > > In subsequent reply [1] Bill states > > While there is some evidence, there is still no convincing proof that there > is an entropy source in this device at all. There is some evidence that > Atmel has inserted a back-door. My advice is to avoid this line of parts > from Atmel for cryptographic use. > > In another message Peter Gutmann asks about ATECC108 [2] and Bill replies [3] > > This part uses the same language to describe the random number generator. > It is "high quality". I think that's pretty funny. > I would be interested in seeing if the new part can generate random numbers > continuously, or if it fails after it's EEPROM wears out like their other > parts. The use of an EEPROM seed is for PWN-ing your RNG, not making it > more secure. > > IMO the comments from the actual reviewer are more relevant than those of the > engineer working for the company which was accused of creating low quality > / backdoored TRNG, at least until the Atmel engineer provides some evaluation > code for the device (which they suggested they might do [4], but never did as > far as I can find). > > Maybe we can instead change the ATECC quality to something like 32? Does that > even make sense? > > Marek > > [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023857.html > [2] https://www.metzdowd.com/pipermail/cryptography/2014-December/023870.html > [3] https://www.metzdowd.com/pipermail/cryptography/2014-December/023879.html > [4] https://www.metzdowd.com/pipermail/cryptography/2014-December/023886.html Bill wrote in his review: "If I made no mistake (and I do make a lot), the "random" data from the Atmel ATSHA204A is highly predictable when you disable the seed update to EEPROM." However, the atmel-sha204a driver doesn't operate the device in that mode. It uses the Random command with seed updates enabled, which is also what the datasheet recommends for highest security: "Microchip recommends that the EEPROM seed always be updated." So the reported behavior doesn't reflect how the driver uses the device. Thanks, Thorsten