Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1WLIUm-0001jv-Nz for bitcoin-development@lists.sourceforge.net; Wed, 05 Mar 2014 20:32:52 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of petertodd.org designates 62.13.149.81 as permitted sender) client-ip=62.13.149.81; envelope-from=pete@petertodd.org; helo=outmail149081.authsmtp.net; Received: from outmail149081.authsmtp.net ([62.13.149.81]) by sog-mx-3.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1WLIUl-0006w2-Ej for bitcoin-development@lists.sourceforge.net; Wed, 05 Mar 2014 20:32:52 +0000 Received: from mail-c235.authsmtp.com (mail-c235.authsmtp.com [62.13.128.235]) by punt18.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s25KWiPr007436; Wed, 5 Mar 2014 20:32:44 GMT Received: from tilt ([64.210.40.106]) (authenticated bits=128) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s25KWPt8065532 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Wed, 5 Mar 2014 20:32:36 GMT Date: Wed, 5 Mar 2014 15:32:22 -0500 From: Peter Todd To: Gregory Maxwell Message-ID: <20140305203222.GD24917@tilt> References: <53174F20.10207@gmail.com> <20140305193910.GA24917@tilt> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="AkbCVLjbJ9qUtAXD" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Server-Quench: 4cb9dfc4-a4a5-11e3-b802-002590a15da7 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aQdMdgcUFVQGAgsB AmIbWVReU197XWI7 bQ5PbwRdfE5OQQRq VldMSlVNFUsrAxl6 YX5aWhl0cgBFejBx Y0ViXj5fDxZzIRAu RlMFETwDeGZhPWMC AkhYdR5UcAFPdx8U a1UrBXRDAzANdhES HhM4ODE3eDlSNilR RRkIIFQOdA4tEyF0 XBEOEH0kHUQDQSg3 ZxU6NlcXHw4NMkwu eVAoXxoCPhQVFABE fQlnATNSIFgHDykm HBgy X-Authentic-SMTP: 61633532353630.1023:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 64.210.40.106/587 X-AuthVirus-Status: No virus detected - but ensure you scan with your own anti-virus system. 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See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.6 RCVD_IN_SORBS_WEB RBL: SORBS: sender is an abusable web server [64.210.40.106 listed in dnsbl.sorbs.net] -0.0 SPF_PASS SPF: sender matches SPF record X-Headers-End: 1WLIUl-0006w2-Ej Cc: Bitcoin Development Subject: Re: [Bitcoin-development] New side channel attack that can recover Bitcoin keys X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 05 Mar 2014 20:32:52 -0000 --AkbCVLjbJ9qUtAXD Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Mar 05, 2014 at 11:51:25AM -0800, Gregory Maxwell wrote: > On Wed, Mar 5, 2014 at 11:39 AM, Peter Todd wrote: > > If you're following good practices you're not particularly vulneable to > > it, if at all, even if you make use of shared hosting. First of all you > > shouldn't be re-using addresses, which means you won't be passing that > > ~200 sig threshold. > > > > More important though is you shouldn't be using single factor Bitcoin > > addresses. Use n-of-m multisig instead and architect your system such >=20 > Both of these things have long been promoted as virtuous in part > because they increase robustness against this sort of thing. >=20 > But while I don't disagree with these things the reality is that many > people do not follow either of these piece of advice and following > them requires behavioral changes that will not be adopted quickly... > so I don't think that advice is especially useful. >=20 > And even if it were=E2=80=94, good security involves defense in depth, so > adding on top of them things like side-channel resistant signing is > important. >=20 > I haven't had a chance to sit down and think through it completely but > I believe oleganza's recent blind signature scheme for ECDSA may be > helpful (http://oleganza.com/blind-ecdsa-draft-v2.pdf): >=20 > The idea is that instead of (or in addition to=E2=80=94 belt and suspende= rs) > making the signing constant time, you use the blinding scheme to first > locally blind the private key and point being signed, then sign, then > unblind. This way even if you are reusing a key every signing > operation is handling different private data... and the only point > where unblinded private data is handled is a simple scalar addition. That's nice, but I wrote my advice to show people how even if they don't know any crypto beyond what the "black boxes" do - the absolute minimum you need to know to write any Bitcoin software - you can still defend yourself against that attack and many others. Point is you can architect systems that remain secure even when parts of them fail, and you don't need any special cryptographic background to do so - any competent programmer can. Meanwhile, if you're not willing to take those simple steps, the Bitcoin community damn well should look down on your amateur efforts, e.g. Coinbase and EasyWallet. --=20 'peter'[:-1]@petertodd.org 000000000000000f9102d27cfd61ea9e8bb324593593ca3ce6ba53153ff251b3 --AkbCVLjbJ9qUtAXD Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBCAAGBQJTF4nWAAoJECSBQD2l8JH7gJkH/3VzB+d9raGrN6szwkvMGLs8 do36FrD8S3+EyXvK9q2S9NyXWRvZLXd3XLRhHLx3MYp1aUDuu6A8UyVyv3Chk4oo MpaQwt/nF/a0OB1yFgf2rsnlDVIhoOj7AM0RCzrY71iU5I7nT0VVHwQOt4X1llgB UnGAAKuzhgRZukd8FkxQxbZvUn9cCBk+6cah8vES/U0ELx1S9Y9BSTFEaYRevyoL 5h5eAkZUtziz+jdQ0QUVrJejXm31mqgNQ1Ig17YOqLQpJqeS3jgFW31sqKKVzaCP ex1EcbH2FxNV+XNQy5J64istonJNpC6sBz5qjaKyfN6Kwmpa8BAKY1DCpfa4ZEY= =+fZf -----END PGP SIGNATURE----- --AkbCVLjbJ9qUtAXD--