From: Markus Stockhausen Subject: AW: [PATCH v1 2/7] AES for PPC/SPE - aes tables Date: Mon, 16 Feb 2015 17:18:48 +0000 Message-ID: <12EF8D94C6F8734FB2FF37B9FBEDD1735F9DF098@EXCHANGE.collogia.de> References: <063D6719AE5E284EB5DD2968C1650D6D1CAE46B2@AcuExch.aculab.com>,<20150216143706.GA3609@gate.crashing.org> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_NextPartTM-000-d0fb26b8-9b33-4b13-a2b2-3b353007fa76" Cc: "linux-crypto@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" To: Segher Boessenkool , David Laight Return-path: Received: from mailrelay.collogia.de ([194.8.207.98]:10570 "HELO mailrelay.collogia.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753197AbbBPRSv (ORCPT ); Mon, 16 Feb 2015 12:18:51 -0500 In-Reply-To: <20150216143706.GA3609@gate.crashing.org> Content-Language: de-DE Sender: linux-crypto-owner@vger.kernel.org List-ID: This is a multi-part message in MIME format. ------=_NextPartTM-000-d0fb26b8-9b33-4b13-a2b2-3b353007fa76 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable > Von: linux-crypto-owner@vger.kernel.org [linux-crypto-owner@vger.kernel.o= rg]" im Auftrag von "Segher Boessenkool [segher@kernel.crashing.o= rg]=0A= > Gesendet: Montag, 16. Februar 2015 15:37=0A= > An: David Laight=0A= > Cc: Markus Stockhausen; linux-crypto@vger.kernel.org; linuxppc-dev@lists.= ozlabs.org=0A= > Betreff: Re: [PATCH v1 2/7] AES for PPC/SPE - aes tables=0A= > =0A= > On Mon, Feb 16, 2015 at 02:19:50PM +0000, David Laight wrote:=0A= > > From: Markus Stockhausen=0A= > > > 4K AES tables for big endian=0A= > >=0A= > > I can't help feeling that you could give more information about how the= =0A= > > values are generated.=0A= > =0A= > ... and an explanation of why this does not open you up to a timing attac= k?=0A= =0A= Good points,=0A= =0A= the tables are only big endian reversed ones of those found in crypto/aes_g= eneric.c.=0A= =0A= Regarding timing attacks: I understand, that reducing AES table sizes for a= constant =0A= AES processing time is important to avoid cache timing attacks. Hopefully t= he =0A= following points will mitigate the concern.=0A= =0A= Target architecture are low performance e500 cores without available caam = =0A= features. These can currently use only aes-generic module. That one depends= =0A= on 16K T-tables. 2*4K for encryption and 2*4K for decryption. The new modul= e=0A= reduces the T-table sizes to 8K+256 bytes. Far away from a minimal 256 byte= =0A= S-BOX but at least an improvement.=0A= =0A= To narrow it down further. Intended use is for cheap routers. So no multius= er =0A= environments where a malicous process could drive complex flush+reload =0A= attacks. In case someone gains unallowed access there will be a lot of othe= r =0A= and simpler ways to compromise the system.=0A= =0A= In case that is sufficient for you I will add respective notes into a patch= v2.=0A= =0A= Markus= ------=_NextPartTM-000-d0fb26b8-9b33-4b13-a2b2-3b353007fa76 Content-Type: text/plain; name="InterScan_Disclaimer.txt" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="InterScan_Disclaimer.txt" **************************************************************************** Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet. Über das Internet versandte E-Mails können unter fremden Namen erstellt oder manipuliert werden. Deshalb ist diese als E-Mail verschickte Nachricht keine rechtsverbindliche Willenserklärung. Collogia Unternehmensberatung AG Ubierring 11 D-50678 Köln Vorstand: Kadir Akin Dr. Michael Höhnerbach Vorsitzender des Aufsichtsrates: Hans Kristian Langva Registergericht: Amtsgericht Köln Registernummer: HRB 52 497 This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. e-mails sent over the internet may have been written under a wrong name or been manipulated. That is why this message sent as an e-mail is not a legally binding declaration of intention. Collogia Unternehmensberatung AG Ubierring 11 D-50678 Köln executive board: Kadir Akin Dr. Michael Höhnerbach President of the supervisory board: Hans Kristian Langva Registry office: district court Cologne Register number: HRB 52 497 **************************************************************************** ------=_NextPartTM-000-d0fb26b8-9b33-4b13-a2b2-3b353007fa76--