From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1W2ntt-00013y-Pg for bitcoin-development@lists.sourceforge.net; Mon, 13 Jan 2014 20:14:21 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of petertodd.org designates 62.13.148.154 as permitted sender) client-ip=62.13.148.154; envelope-from=pete@petertodd.org; helo=outmail148154.authsmtp.co.uk; Received: from outmail148154.authsmtp.co.uk ([62.13.148.154]) by sog-mx-4.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1W2nts-0001Hn-FU for bitcoin-development@lists.sourceforge.net; Mon, 13 Jan 2014 20:14:21 +0000 Received: from mail-c235.authsmtp.com (mail-c235.authsmtp.com [62.13.128.235]) by punt15.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s0DKEBNc000722; Mon, 13 Jan 2014 20:14:11 GMT Received: from petertodd.org (petertodd.org [174.129.28.249]) (authenticated bits=128) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s0DKE8VB030920 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Mon, 13 Jan 2014 20:14:10 GMT Date: Mon, 13 Jan 2014 15:14:08 -0500 From: Peter Todd To: Alan Reiner Message-ID: <20140113201407.GB7941@petertodd.org> References: <20140106120338.GA14918@savin> <20140110102037.GB25749@savin> <20140113194049.GJ38964@giles.gnomon.org.uk> <52D4458C.6010909@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="8P1HSweYDcXXzwPJ" Content-Disposition: inline In-Reply-To: <52D4458C.6010909@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Server-Quench: 43dc8a18-7c8f-11e3-b802-002590a15da7 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aAdMdwEUElQaAgsB AmIbWVReUVl7WGI7 ag1VcwRfa1RMVxto VEFWR1pVCwQmQhx1 fWsWNGtydAVPen4+ ZEVjWHEVWEcuJk4s Q0ZJEj4OM3phaTUc TRJQdwFJcANIexZF O1F6ACIKLwdSbGoL NQ4vNDcwO3BTJTpY RgYVKF8UXXNDJSIx ThQeHX0GEUEfSj4o IgdO X-Authentic-SMTP: 61633532353630.1023:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 174.129.28.249/587 X-AuthVirus-Status: No virus detected - but ensure you scan with your own anti-virus system. X-Spam-Score: -1.5 (-) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain -0.0 SPF_PASS SPF: sender matches SPF record X-Headers-End: 1W2nts-0001Hn-FU Cc: bitcoin-development@lists.sourceforge.net Subject: Re: [Bitcoin-development] Stealth Addresses 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: Mon, 13 Jan 2014 20:14:22 -0000 --8P1HSweYDcXXzwPJ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jan 13, 2014 at 02:59:08PM -0500, Alan Reiner wrote: > How is this different from the proposal I have made? >=20 > You distribute the root public key (but not chaincode!) of a BIP32 > branch. You can put your root key on a business card if you want. Then > when someone wants to pay you, you simply give them the multiplier and > root key (they already have the root key, but should verify). The > multiplier does not reveal the chaincode, thus keeping it private, but > it does allow them to confirm that the final address they are paying is > derived from that root key they know belongs to you ("Please pay address > X; oh btw, X=3DrootKey*mult"). >=20 > You can /choose/ to reveal that a given payment address is linked to > your root key without any compromise of privacy. Or you can choose to > ignore it and just give them a bare address the old way and still > maintain privacy. What advantages does "stealth addresses" have over > this scheme? You could extend it using some kind of deterministic > sub-branching and/or ECDH to create multiple payment addresses without > querying the payee.=20 Basically stealth addresses *are* your scheme, using the blockchain as a low or even no overhead communication channel for the payor to give the payee that multiplier without bidirectional communication. In the business card example I can't easily take your business card and just send you some money without that transaction being linked to public information. (your business card) > I had planned to implement this system and push for people to accept it > because I don't see any downsides to it. It can easily be integrated > into a WoT (with signed root keys), or CA system piggybacking on SSL. WoT is a perfect example of the problem: if you put BIP32 branch payment info into my OpenPGP key I can't pay you securely and reliably without making the transaction public. The best I can do is pick a nonce and pay X=3DrootKey*nonce, communicating to you the nonce later - this isn't reliable because if I or you lose the nonce the funds are lost. With stealth addresses the user experience can be as simple as you telling me on the phone "hey! send me that 0.234 BTC you owe me!", me clicking on "Send to Alan Reiner (verified by PGP)" (perhaps again on my off-line second factor device for a multi-sig wallet) and tellling you "OK, sent". Even if your phone has been wiretapped, the attacker still didn't learn exactly what transaction was actually used to make the payment - a big advantage over per-tx nonce stuff. --=20 'peter'[:-1]@petertodd.org 00000000000000023d5a8bbe131414328a6c50a2741933ba03775afd3c3db395 --8P1HSweYDcXXzwPJ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQEcBAEBCAAGBQJS1EkPAAoJEBmcgzuo5/CFUMAIANDvoWtXdbFgtfsxrGnobWM/ J9T2YVjTJa0xeg2dt0efDMwkoYRNGTuQWm4dCxHv9b58qP3JY1UK5FxQjYzzQMUR fjFKadW0eEyMLCY064IsXTxnGjUBJK/L35LAhbUJ3oSis7zs9FUhzh+lLRLzKNUK znLAHZdnDxcrMtSL1DciCL3Wc9pXJ48s9G66wsfS6yTAOmayaxFJRC9rb+lTUreu IZ8kuInaw5Qm7aQV+Trid4e+YtxLzClQgtl2ExQJXlOTIgNcvxwal1cz6AYDYjIM VGKYfI3hSxahBe2RwiOkaWZaXiWC8fNIf0f7o6neRyXi6fiPaiCRaAKw9GZpOzE= =d/Sz -----END PGP SIGNATURE----- --8P1HSweYDcXXzwPJ--