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-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1UZSFp-0002V2-FQ for bitcoin-development@lists.sourceforge.net; Mon, 06 May 2013 20:43:25 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of petertodd.org designates 62.13.149.95 as permitted sender) client-ip=62.13.149.95; envelope-from=pete@petertodd.org; helo=outmail149095.authsmtp.com; Received: from outmail149095.authsmtp.com ([62.13.149.95]) by sog-mx-3.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1UZSFo-0001cs-0U for bitcoin-development@lists.sourceforge.net; Mon, 06 May 2013 20:43:25 +0000 Received: from mail-c232.authsmtp.com (mail-c232.authsmtp.com [62.13.128.232]) by punt7.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id r46KhCan084780; Mon, 6 May 2013 21:43:12 +0100 (BST) 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 r46Kh7Pg035476 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Mon, 6 May 2013 21:43:10 +0100 (BST) Date: Mon, 6 May 2013 16:43:07 -0400 From: Peter Todd To: Adam Back Message-ID: <20130506204307.GA23287@petertodd.org> References: <20130506163732.GB5193@petertodd.org> <20130506171943.GA22505@petertodd.org> <20130506175331.GB22505@petertodd.org> <20130506183222.GB3797@netbook.cypherspace.org> <20130506190857.GA23095@petertodd.org> <20130506195003.GB4583@netbook.cypherspace.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="RnlQjJ0d97Da+TV1" Content-Disposition: inline In-Reply-To: <20130506195003.GB4583@netbook.cypherspace.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Server-Quench: 90a1c780-b68d-11e2-b10b-0025903375e2 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aQdMdgQUFVQNAgsB AmUbWVVeVF57WGM7 ag1VcwRfa1RMVxto VEFWR1pVCwQmQxgH fUYZMk5ydABCf3g+ ZE5jWHAVVUQrdBV6 Sk5JR2sOMXphaTUd TRJZd1FJcANIexZF aVN4USYPLwdSbGoL NQ4vNDcwO3BTJTpY RgYVKF8UXXNDMj8n TBccEC8+WkQJSz97 NxUtKVMABw5RLUwp YxMaVEgGMhQfQgdf A1ovSCFePREZXTct AA8SW0kSHSYcKQAA X-Authentic-SMTP: 61633532353630.1019:706 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: 1UZSFo-0001cs-0U Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] Discovery/addr packets (was: Service bits for pruned nodes) 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, 06 May 2013 20:43:25 -0000 --RnlQjJ0d97Da+TV1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, May 06, 2013 at 09:50:03PM +0200, Adam Back wrote: > Of course you'd probably need zerocoin to stand much chance of proving an > address private key of an unlinked coin was in the double-spend disclosed > attribute in the first place, and as we know zerocoin is not that efficie= nt. Sounds like a lot of research potential with many far off possiblities. :) > >Make the node identity expensive to obtain. For instance, construct PoW's > >including the node pubkey somehow, >=20 > that could be easily done with the work of creating a vanity address. eg > address containing many leading 0s. Bitcoin is interesting because it provides a nice way to determine the value of a proof-of-work. Lets suppose you have a digest D and want to create a proof of work for that digest. 1) Select a block B1 that is reasonably deep in the blockchain. (You don't want it getting re-orged out of existence) Six blocks deep is probably plenty. 2) Construct an invalid block header, BP, with SHA256(B1 | D) as the previous block hash. All other fields can be set to whatever is required by your hashing unit. (the merkle root would be an option too, but many hashing setups can't put arbitrary data into it) 3) Hash until you have found the PoW with the difficulty you want. 4) Timestamp BP in the blockchain, resulting in a merkle path M leading to a subsequent block B2. (1) Now determining the value of D has a nice compact proof: B1, BP and M and B2. Taking the minimum of the difficulties of B1 and B2 (in case they cross a retarget boundry; don't want to create strange incentives) determine the expected return in Bitcoins from the block reward had the hasher solved valid blocks instead and you can determine exactly how much the proof-of-work was worth, kinda... Things get a bit complex from here on. First of all there isn't a compact proof that will tell you how much the fees of solving that block would have been worth, and there can't be because miners can easily manipulate the apparent fees of a block in both directions. Also as with fidelity bonds (https://en.bitcoin.it/wiki/Fidelity_bonds) the question of which value to use, historic or current, is important too. If you use the Bitcoin face value increases or decreases of the value of a Bitcoin are arguably distorting. On the other hand, if you use historical exchange rates, which currency do you use and where do you get trustworthy historical exchange rate data? (2) 1) See https://github.com/opentimestamps 2) Which reminds me, I do need to get around to bugging Mt. Gox to PGP sign their exchange rate data and timestamp it properly, or do one or both myself. It should be archived at archive.org or something too, heck, the blockchain should be too, although timestamping that will require a bit more work... --=20 'peter'[:-1]@petertodd.org 0000000000000190ee1bf5262b2557eb69b49d0e14e1d644ec44a8488f7f5181 --RnlQjJ0d97Da+TV1 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iEYEARECAAYFAlGIFdsACgkQpEFN739thowUggCfUwEWmA+k8vhyoeTHKZgMHxQi 3aoAnRPfR3gmhcnohqHTNXL8BNufE3Kn =fQgT -----END PGP SIGNATURE----- --RnlQjJ0d97Da+TV1--