Re: [keyassure] Opening issue #21: "Need to specify which crypto

Martin Rex <mrex@sap.com> Wed, 02 March 2011 17:23 UTC

Return-Path: <mrex@sap.com>
X-Original-To: keyassure@core3.amsl.com
Delivered-To: keyassure@core3.amsl.com
Received: from localhost (localhost [127.0.0.1]) by core3.amsl.com (Postfix) with ESMTP id 7D45E3A6857 for <keyassure@core3.amsl.com>; Wed, 2 Mar 2011 09:23:53 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -10.234
X-Spam-Level:
X-Spam-Status: No, score=-10.234 tagged_above=-999 required=5 tests=[AWL=0.015, BAYES_00=-2.599, HELO_EQ_DE=0.35, RCVD_IN_DNSWL_HI=-8]
Received: from mail.ietf.org ([64.170.98.32]) by localhost (core3.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id B0B8IwuInEug for <keyassure@core3.amsl.com>; Wed, 2 Mar 2011 09:23:52 -0800 (PST)
Received: from smtpde02.sap-ag.de (smtpde02.sap-ag.de [155.56.68.140]) by core3.amsl.com (Postfix) with ESMTP id EBF9D3A6855 for <keyassure@ietf.org>; Wed, 2 Mar 2011 09:23:51 -0800 (PST)
Received: from mail.sap.corp by smtpde02.sap-ag.de (26) with ESMTP id p22HOuQf013826 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 2 Mar 2011 18:24:56 +0100 (MET)
From: Martin Rex <mrex@sap.com>
Message-Id: <201103021724.p22HOttB009647@fs4113.wdf.sap.corp>
To: hallam@gmail.com (Phillip Hallam-Baker)
Date: Wed, 2 Mar 2011 18:24:55 +0100 (MET)
In-Reply-To: <AANLkTikHANKvT49P5RUwjxRt5oEMFxV5dYQLcCXixLSA@mail.gmail.com> from "Phillip Hallam-Baker" at Mar 2, 11 12:04:56 pm
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
X-SAP: out
Cc: keyassure@ietf.org
Subject: Re: [keyassure] Opening issue #21: "Need to specify which crypto
X-BeenThere: keyassure@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
Reply-To: mrex@sap.com
List-Id: Key Assurance With DNSSEC <keyassure.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/listinfo/keyassure>, <mailto:keyassure-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/keyassure>
List-Post: <mailto:keyassure@ietf.org>
List-Help: <mailto:keyassure-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/keyassure>, <mailto:keyassure-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 02 Mar 2011 17:23:53 -0000

Phillip Hallam-Baker wrote:
> 
> The use of MD2 in a self signed cert has little risk as far as use of
> the cert itself goes since it only serves as proof of possession which
> is only relevant when the browser provider chooses to install it in
> the browser.

In the universe where I live, there exist collision attacks against MD2.
 (check http://en.wikipedia.org/wiki/MD2_%28cryptography%29)

So an RSA-key for which a PKCS#1 encrypted MD2 signature has been
published is a real security problem and ought to have been discarded
long ago.

Else someone could try to use the preimage attack to issue himself
an intermediate CA cert under such a root cert, reusing the md2-based
signature on the RootCA cert.

I would REALLY like to kill md2withRsaEncryption as a digital
signature algorithm from our PKI implementation, like I did
with all of md4-based digital signature algorithms.


Getting rid of "tainted" RSA keys is also important.

Why do you think that FIPS 186-3 says that you are not allowed
to use an RSA keypair for both PKCS-v1.5 and PKCS-PSS signatures?
Because you "taint" your RSA key on the first time that you use it
for a weak scheme.

-Martin