From mboxrd@z Thu Jan 1 00:00:00 1970 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 <pete@petertodd.org>) id 1WUYR9-00089W-27 for bitcoin-development@lists.sourceforge.net; Mon, 31 Mar 2014 09:23:23 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of petertodd.org designates 62.13.148.106 as permitted sender) client-ip=62.13.148.106; envelope-from=pete@petertodd.org; helo=outmail148106.authsmtp.co.uk; Received: from outmail148106.authsmtp.co.uk ([62.13.148.106]) by sog-mx-3.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1WUYR7-00075z-N1 for bitcoin-development@lists.sourceforge.net; Mon, 31 Mar 2014 09:23:23 +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 s2V9NFKE026678; Mon, 31 Mar 2014 10:23:15 +0100 (BST) Received: from tilt (cust.static.84-253-54-151.cybernet.ch [84.253.54.151]) (authenticated bits=128) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s2V9N9WT037516 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Mon, 31 Mar 2014 10:23:11 +0100 (BST) Date: Mon, 31 Mar 2014 11:23:09 +0200 From: Peter Todd <pete@petertodd.org> To: Mike Hearn <mike@plan99.net> Message-ID: <20140331092309.GA19482@tilt> References: <CANEZrP0AwR3WgHfwYWcrC9Z_MHPDwymWXAQwp7D8XZ+o2FsK8g@mail.gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="9amGYk9869ThD9tj" Content-Disposition: inline In-Reply-To: <CANEZrP0AwR3WgHfwYWcrC9Z_MHPDwymWXAQwp7D8XZ+o2FsK8g@mail.gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Server-Quench: 14477b03-b8b6-11e3-b802-002590a15da7 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aAdMdQMUFVQGAgsB AmIbWlReUl57WGI7 Yw5PbwBefE9KQQRv UVdMSlVNFUsrA3oI eBd5NhlxcABHfjB5 Yk9gEHFfWEN9J0Z+ XxxcR2sbZGY1a31N WEBaagNUcgZDfk5E bwQuUz1vNG8XDQg5 AwQ0PjZ0MThBJSBS WgQAK04nCWwqJnZj H1gYEDsyG0FNSSQ+ KxBO X-Authentic-SMTP: 61633532353630.1023:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 84.253.54.151/587 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: 1WUYR7-00075z-N1 Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net> Subject: Re: [Bitcoin-development] BIP 70 refund field X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: <bitcoin-development.lists.sourceforge.net> List-Unsubscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>, <mailto:bitcoin-development-request@lists.sourceforge.net?subject=unsubscribe> List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=bitcoin-development> List-Post: <mailto:bitcoin-development@lists.sourceforge.net> List-Help: <mailto:bitcoin-development-request@lists.sourceforge.net?subject=help> List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>, <mailto:bitcoin-development-request@lists.sourceforge.net?subject=subscribe> X-List-Received-Date: Mon, 31 Mar 2014 09:23:23 -0000 --9amGYk9869ThD9tj Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 28, 2014 at 12:07:04PM +0100, Mike Hearn wrote: > Though I am loathe to go back and redesign this part of BIP 70 so soon > after we shipped v1, it seems to me like the refund feature may be hard to > implement on phones if there's no time limit for when you can receive a > refund. Otherwise a wallet has to be looking out for refunds for payments > you may have made years ago. So perhaps we should add a new refund field > that embeds a PaymentDetails structure instead of being just a list of > outputs. >=20 > We could try and solve this problem some other way purely internally, by > doing a kind of wallet-specific swapping process in which things like Blo= om > filters are calculated without all keys in them being held in memory at > once (perhaps caching filters for old parts of the key chain on disk), so > you can have "infinite" wallets, but eventually the huge Bloom filters th= at > would result would hurt efficiency in other ways. So key expiry seems > pretty fundamental to scalability. One of the main goals of steath addresses is actually scalability. In particular in the refund address case you would use stealth addresses with a per-order UUID so that refunds can be detected cheaply by just scanning for payments to your (single) stealth address, then when those payments are detected, check the UUID against a on-disk database. A 64-bit "UUID" is probably fine, although unfortunately with OP_RETURN quite unexpectedly dropped to 40 bytes the standard needs to change; might have to compromise on privacy and re-use a txin pubkey to make things fit. --=20 'peter'[:-1]@petertodd.org 0000000000000000f4f5ba334791a4102917e4d3f22f6ad7f2c4f15d97307fe2 --9amGYk9869ThD9tj Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQGcBAEBCAAGBQJTOTP4AAoJEGJeboN5AaHK3BwL/2cufakUZftLPL7iC9E1R/Bd Y2CleAYIpbfJ+vGRmFCw3hD0BMufGyU0HFvPBkz5s5vfsDtwZvDuiqENlH1JAU2I qtG6hGmtPDEiQxlPSRpvgfy6sDMetkQsctZ1QjOI5bdyoztcub7CDPEVzYwW9u+w 26rlO56d8ygfasT1gUkGtFiAv7Ytn9MU7FeQrr9iufXb57VOeBAZjSstiWMc9QSX RPIBEAB3n5S/MwOprKh5cB9x62eXiCsOxB+45UtRy/EJh8ht72QCuWmChVP2F0ZF zmcvPjBp3Avwuftiv9Iipkit7Xg8qZiZxkD35JOTXGNN3bgcvoQKnMFNIf8BrviB GERFHCIyv25wPznCsG9uyuLH0Wi3To+qyeo/7gxOSpctoxntV34rAjI2M66tSbvE yO+mVW1kMJPfOzwldCzKgROPtyJjfLzlDTIs0g3AGGZycNlVU1Rvksc2OCgGJ+IB a6QwD6gHg3qdPwYxAFd7Ku/FZ3n7NG6Qwi+8LbNkWA== =N4Oj -----END PGP SIGNATURE----- --9amGYk9869ThD9tj--