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-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Wcz69-0006DV-5m for bitcoin-development@lists.sourceforge.net; Wed, 23 Apr 2014 15:28:33 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of petertodd.org designates 62.13.148.96 as permitted sender) client-ip=62.13.148.96; envelope-from=pete@petertodd.org; helo=outmail148096.authsmtp.net; Received: from outmail148096.authsmtp.net ([62.13.148.96]) by sog-mx-4.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1Wcz67-0005Hn-7H for bitcoin-development@lists.sourceforge.net; Wed, 23 Apr 2014 15:28:33 +0000 Received: from mail-c235.authsmtp.com (mail-c235.authsmtp.com [62.13.128.235]) by punt17.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s3NFSOSP090302; Wed, 23 Apr 2014 16:28:24 +0100 (BST) Received: from savin (76-10-178-109.dsl.teksavvy.com [76.10.178.109]) (authenticated bits=128) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s3NFSKcB051705 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Wed, 23 Apr 2014 16:28:22 +0100 (BST) Date: Wed, 23 Apr 2014 11:28:18 -0400 From: Peter Todd To: Alex Mizrahi Message-ID: <20140423152818.GF19430@savin> References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="KJY2Ze80yH5MUxol" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Server-Quench: e80bd6c7-cafb-11e3-b802-002590a15da7 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aAdMdAEUGUUGAgsB AmIbWlJeUlV7W2E7 bAxPbAVDY01GQQRq WVdMSlVNFUsrAmJ3 ZWVNIBl3dgJGfTBx YERnVj4OVEQoIUAu RVMHRDtUeGZhPWMC AkhYdR5UcAFPdx8U a1UrBXRDAzANdhES HhM4ODE3eDlSNilR RRkIIFQOdA4gGT86 TRkZEH01EEQBQyI4 JgAnLVhUAEFZPkQp Olw8Q1sXPlc8CwtY ElAvSCZFO1AKRDFD X-Authentic-SMTP: 61633532353630.1023:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 76.10.178.109/587 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: 1Wcz67-0005Hn-7H Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] Coinbase reallocation to discourage Finney attacks 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, 23 Apr 2014 15:28:33 -0000 --KJY2Ze80yH5MUxol Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 23, 2014 at 06:04:00PM +0300, Alex Mizrahi wrote: > This is outright ridiculous. >=20 > Zero-confirmation double-spending is a small problem, and possible > solutions are known. (E.g. trusted third party + multi-sig addresses for > small-value transactions.) Also replace-by-fee scorched earth. > On the other hand, protocol changes like described above might have > game-theoretical implications which are non-trivial and hard to understan= d. To put it mildly. :) Beyond the obvious issues with adding mechanisms for miners to vote on what blacklists they wish to apply, it's interesting to consider how trying to make zeroconf transactions secure directly is quite close to changing the block interval. Like the blocksize that's a fundemental economic parameter of the system - how low-latency and well connected you must be to be allowed to mine. Even in a scheme where the punishment for allowing a double-spend was somehow applied perfectly fairly, you'd still be favoring large well-connected miners in a very similar way to reducing the block interval. > The above approach works as long as the majority of hashpower is honest, > > defined to mean, working to stop double spending. This is the same secu= rity > > property as described in the white paper, thus this introduces no new > > security assumptions. > > >=20 > No. Bitcoin should work if miners are merely individually rational, i.e. > they try to maximize their pay-offs without colluding with others. It's worth noting that the academic efforts studying Bitcoin are spending quite a bit of effort focused on the incentive compatibility of various mechanisms in the protocol: https://github.com/citp/bitcoin-sok/iss= ues/5 There's solid consensus in the academic community that Bitcoin can't just depend on notions of "honesty" to work. > I guess word "honest" might have different meanings, that can be a source > of confusing. > 1. Honest -- not trying to destroy bitcoin > 2. Honest -- following rules which are not required by the protocol What exactly those rules are is up for debate too. Right now if, say, just 5% of Bitcoin miners were willing to accept Colored Coin transactions you could still use Colored Coins. The other 95% may want to block said transactions, but there's huge practical difficulties in organizing a reorg and ensuring that everyone co-operates; miners have strong incentives to defect if the consensus isn't assured as any miners attempting to reorg are wasting their hashing power if it doesn't succeed. OTOH with a voting scheme the cost to propose that a specific block or a transaction be blacklisted is much lower. In Mike's proposed scheme to not just blacklist, but actually take coinbases it's downright profitable. Rather than being a last resort option, it'll be easy for miners to propose various things be blacklisted, if the vote goes through, great, if it doesn't, no harm done. Obviously that makes blacklists into a much more useful tool and greatly changes the political landscape around them. Remember, if you're operating a publicly known pool, and there's a voting mechanism available to you to blacklist specific blocks, how are you going to resist pressure from your local authorities to do just when there's no cost to you to do so? --=20 'peter'[:-1]@petertodd.org 0000000000000000278031f86c71265f6eaf1fe9ce6cc831dc4f956676a7a7f7 --KJY2Ze80yH5MUxol Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) iQGrBAEBCACVBQJTV9wOXhSAAAAAABUAQGJsb2NraGFzaEBiaXRjb2luLm9yZzAw MDAwMDAwMDAwMDAwMDAyNzgwMzFmODZjNzEyNjVmNmVhZjFmZTljZTZjYzgzMWRj NGY5NTY2NzZhN2E3ZjcvFIAAAAAAFQARcGthLWFkZHJlc3NAZ251cGcub3JncGV0 ZUBwZXRlcnRvZC5vcmcACgkQJIFAPaXwkftR8Af/cVCaxQQdLV7LB5bHOQ2H5NkD tO1TXcu84lRxYjJx0CChOtcoI5oONcVtkNyM+pn+mrVNI/CbIqyBVQZmUW7CGc0m zaSgZII/0dYPUQCi0kXoBrNTRADgvrOKB+/ef9MUVInkuH7iqJuwqSeqA6x4BSXB kTL6VHFLT97Gkrtnw2c+0QmguZXSdw3DwvlL1E6eiwvxlyJwsXfjXsyFJwQ+cjpJ o4WkPZ9EC1gNFpWrccCns0TCxCrG7cAAJ4dq1LPxUkfIjwe7Rk0/Ckye7ae3t3h8 Y8djr1OHoUsAQXhjjOQEeldwnzdTQInQQsuf6LG88mcm6S7AQjcln7Wc5BKw7Q== =ZBka -----END PGP SIGNATURE----- --KJY2Ze80yH5MUxol--