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-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1RIdZw-00073M-AN for bitcoin-development@lists.sourceforge.net; Tue, 25 Oct 2011 09:45:52 +0000 X-ACL-Warn: Received: from vm120.rz.uni-osnabrueck.de ([131.173.17.202] helo=mail-in-4.serv.Uni-Osnabrueck.DE) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1RIdZt-0002pR-Dr for bitcoin-development@lists.sourceforge.net; Tue, 25 Oct 2011 09:45:52 +0000 Received: from vm179.rz.Uni-Osnabrueck.DE (vm179.rz.uni-osnabrueck.de [131.173.16.37]) by mail-in-4.serv.Uni-Osnabrueck.DE (8.13.8/8.13.8) with ESMTP id p9P9jfeV024264 for ; Tue, 25 Oct 2011 11:45:41 +0200 Received: by vm179.rz.Uni-Osnabrueck.DE (Postfix, from userid 48) id 88DBD5C1; Tue, 25 Oct 2011 11:45:41 +0200 (CEST) Received: from 134.106.52.172 (SquirrelMail authenticated user jan) by webmail.uni-osnabrueck.de with HTTP; Tue, 25 Oct 2011 11:45:41 +0200 (CEST) Message-ID: <44190.134.106.52.172.1319535941.squirrel@webmail.uni-osnabrueck.de> Date: Tue, 25 Oct 2011 11:45:41 +0200 (CEST) From: "Jan Vornberger" To: bitcoin-development@lists.sourceforge.net User-Agent: SquirrelMail/1.4.8-5.el5_4.10 MIME-Version: 1.0 Content-Type: text/plain;charset=utf-8 Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal X-PMX-Version: 5.5.9.395186, Antispam-Engine: 2.7.2.376379, Antispam-Data: 2011.10.25.93314 (Univ. Osnabrueck) X-PMX-Spam: Gauge=XI, Probability=11%, Report= PRIORITY_NO_NAME 0.716, BODYTEXTP_SIZE_3000_LESS 0, BODY_SIZE_2000_2999 0, BODY_SIZE_5000_LESS 0, BODY_SIZE_7000_LESS 0, WEBMAIL_SOURCE 0, WEBMAIL_USER_AGENT 0, __ANY_URI 0, __BOUNCE_CHALLENGE_SUBJ 0, __BOUNCE_NDR_SUBJ_EXEMPT 0, __CT 0, __CTE 0, __CT_TEXT_PLAIN 0, __HAS_MSGID 0, __HAS_X_PRIORITY 0, __MIME_TEXT_ONLY 0, __MIME_VERSION 0, __PHISH_SPEAR_HTTP_RECEIVED 0, __PHISH_SPEAR_STRUCTURE_1 0, __PHISH_SPEAR_STRUCTURE_2 0, __SANE_MSGID 0, __TO_MALFORMED_2 0, __TO_NO_NAME 0, __URI_NO_MAILTO 0, __URI_NO_PATH 0, __URI_NO_WWW 0, __USER_AGENT 0 X-PMX-Spam-Level: XI X-Spam-Score: 0.0 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. X-Headers-End: 1RIdZt-0002pR-Dr Subject: Re: [Bitcoin-development] Determine input addresses of a transaction 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: Tue, 25 Oct 2011 09:45:52 -0000 Am Mo, 24.10.2011, 16:55, schrieb Gavin Andresen: >> So my first shot at this is to go through the inputs of a transaction and >> see if the scriptSig field has only two opcodes. If that is the case, I assume that it is of the structure and calculate the Bitcoin address from . >> But then I started to wonder if this is safe. Can this be tricked somehow? > > Sure. There are lots of non-standard scriptPubKey scripts that will validate if given as input: a simple OP_NOP would work (do nothing, then check the top value on the stack and validate if it is not zero-- and is not zero). Aw, I see. So back to the drawing board for me. How about this: I make sure that is a proper signature from a green address key, by bringing my own scriptPubKey of just OP_CHECKSIG, complete the script to be OP_CHECKSIG, and run it and afterwards check the address by looking at ? Would that be safe? (Even if it is a hackish solution that only works for certain type of transactions): > Green addresses could be implemented as a second signature in the scriptSig. You'd have to hack your bitcoin client, but you could generate a transaction that had ... as the input instead of . Interesting suggestion! So if I understand correctly, would be the signature generated from signing the transaction with the key of a green address? Which would allow the rest of the transaction to be completely 'normal' and not require it to use specific inputs as such? Sounds good - I guess I never thought in this direction, as I always assumed doing anything 'non-standard' with the scripting language would create a number of knock-on problems. But you are saying, that this would still be considered standard? I guess I have to study this part of the source code more. Well, I guess I'm torn a little bit between two options: 1) Get something working reasonable fast to detect current green address style transactions. It's fine if it is a little bit of a hack, as long as it's safe, since I don't expect it to be merged with mainline anyway at this point. 2) Rethink how green transactions are created and verified and try to put something 'proper' together which has a chance of being merged at some point. For the moment I was going more with 1) because I got the impression, that green transactions are too controversial at this point to get them included in mainline. Criticism ranging from 'unnecessary, as 0-confirmation transactions are fairly safe today' to 'encourages too much centralization and therefore evil'. So how to people on this list feel about green transactions? Would people be interested in helping me with 2)? Regards, Jan