From: Milan Broz Subject: Re: [PATCH] dm-crypt: disable block encryption with arc4 Date: Mon, 25 Jan 2010 19:39:11 +0100 Message-ID: <4B5DE54F.7050206@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: dm-devel@redhat.com, Alasdair G Kergon , linux-crypto@vger.kernel.org To: Mikulas Patocka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:32209 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752940Ab0AYSjT (ORCPT ); Mon, 25 Jan 2010 13:39:19 -0500 Received: from int-mx08.intmail.prod.int.phx2.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o0PIdIaW032444 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 25 Jan 2010 13:39:18 -0500 In-Reply-To: Sender: linux-crypto-owner@vger.kernel.org List-ID: On 01/25/2010 07:29 PM, Mikulas Patocka wrote: > Hi > > When using arc4 to encrypt a block device, the resulting device is > unreliable. It reads garbage. That's because arc4 is a stream cipher, if > you write something, it advances its state and if you attempt to decrypt > the same sector, it uses new state that is different. > > This patch disables the use of arc4 on block devices. arc4 again. it is simply not a block cipher:-) This should be solved inside cryptoAPI and not blacklist it in dm-crypt, see that thread http://article.gmane.org/gmane.linux.kernel.cryptoapi/3441 Milan