From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1RTCLm-0006Pn-OT for bitcoin-development@lists.sourceforge.net; Wed, 23 Nov 2011 12:54:54 +0000 Received-SPF: pass (sog-mx-2.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.214.47 as permitted sender) client-ip=209.85.214.47; envelope-from=andyparkins@gmail.com; helo=mail-bw0-f47.google.com; Received: from mail-bw0-f47.google.com ([209.85.214.47]) by sog-mx-2.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1RTCLm-0002CQ-09 for bitcoin-development@lists.sourceforge.net; Wed, 23 Nov 2011 12:54:54 +0000 Received: by bkbzs2 with SMTP id zs2so1557221bkb.34 for ; Wed, 23 Nov 2011 04:54:47 -0800 (PST) Received: by 10.204.152.25 with SMTP id e25mr24469280bkw.51.1322052887563; Wed, 23 Nov 2011 04:54:47 -0800 (PST) Received: from dvr.localnet (mail.360visiontechnology.com. [92.42.121.178]) by mx.google.com with ESMTPS id x14sm12776819bkf.10.2011.11.23.04.54.42 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 23 Nov 2011 04:54:43 -0800 (PST) From: Andy Parkins To: Jorge =?iso-8859-1?q?Tim=F3n?= Date: Wed, 23 Nov 2011 12:54:41 +0000 User-Agent: KMail/1.13.6 (Linux/3.0.0-1-686-pae; KDE/4.6.3; i686; ; ) References: <201111231035.48690.andyparkins@gmail.com> <201111231130.58785.andyparkins@gmail.com> In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1588240.KrQuzvx5lf"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <201111231254.41426.andyparkins@gmail.com> X-Spam-Score: -1.6 (-) 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 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (andyparkins[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1RTCLm-0002CQ-09 Cc: bitcoin-development@lists.sourceforge.net Subject: Re: [Bitcoin-development] Addressing rapid changes in mining power 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 Nov 2011 12:54:54 -0000 --nextPart1588240.KrQuzvx5lf Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable On 2011 November 23 Wednesday, Jorge Tim=F3n wrote: > With the current system, the timestamp can also be cheated, but miners > have no direct incentive to do it. With your system, they increase > their probability of mining a block by putting a false timestamp. > Also, where's the network clock you're talking about? Isn't it the > timestamps in the blockchain? (1) The "probability of mining a block" is old-think. The probability of=20 mining a block is 100% in my system. Instead, it becomes "the probability = of=20 your block being the hardest" and that requires actual hashing power=20 regardless of the timestamp you write on the block. I could write that my= =20 block was generated next year; but I can't fake the hashing power it needs = to=20 generate one year's worth of hashes. If chain difficulty were summed correctly (sum(log(difficulty)), I guess),= =20 then time makes not the slightest difference anyway. You can issue blocks = at=20 any time with any difficulty, and the "hardest" chain always wins. The blo= ck=20 period can be anything, and it is only the block reward that makes it=20 necessary to pick a particular period for block issuing (even that could be= =20 worked around I guess with a variable reward, but why bother?). (2) For the network clock; see util.cpp:GetAdjustedTime(). (3) Current clients do have an incentive: more time. The more time they ge= t,=20 the more hashes they can try. The current client already checks the=20 timestamp: main.cpp:CBlock::CheckBlock() // Check timestamp if (GetBlockTime() > GetAdjustedTime() + 2 * 60 * 60) return error("CheckBlock() : block timestamp too far in the future"= ); My suggestion only requires that the two hour window be reduced; and a lowe= r=20 limit to be added. Also: while the miners have an incentive to lie about t= he=20 time, the nodes they broadcast to have an incentive to reject mistimed bloc= ks,=20 so you won't gain much by lying to your peers since your block won't be=20 accepted -- the incentive is therefore removed. Note: my system also prevents an attack that is possible with current bitco= in:=20 recalculating the entire chain. Let's say Visa want to take over bitcoin. = =20 They buy enough computing power to significantly beat the current bitcoin=20 network; then they start recalculating the entire block chain; since early= =20 blocks were low difficulty, it's not that hard to do. Once they overtake t= he=20 real chain, they have effectively undone all previous transactions. (I'm n= ot=20 suggesting this is likely; and it's actually mitigated by the hard-coded bl= ock=20 hashes). The point is that blocks are only generatable for the time when t= he=20 rest of the network is willing to add them to the chain. Andy =2D-=20 Dr Andy Parkins andyparkins@gmail.com --nextPart1588240.KrQuzvx5lf Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iEYEABECAAYFAk7M7REACgkQwQJ9gE9xL21CQQCgoI2nbLFSsjT+DL7ljd6rP63o Mq0An0X/CaOv6y9rFaQ+nre9KuvzzpCt =858G -----END PGP SIGNATURE----- --nextPart1588240.KrQuzvx5lf--