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[92.42.121.178]) by mx.google.com with ESMTPS id jb5sm16215035lab.15.2011.11.23.07.29.48 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 23 Nov 2011 07:29:48 -0800 (PST) From: Andy Parkins To: Jorge =?iso-8859-1?q?Tim=F3n?= Date: Wed, 23 Nov 2011 15:29:45 +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> <201111231254.41426.andyparkins@gmail.com> In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart2567792.LKsXHrLWy7"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <201111231529.46154.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: 1RTElo-0002MR-3i 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 15:29:56 -0000 --nextPart2567792.LKsXHrLWy7 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable On 2011 November 23 Wednesday, Jorge Tim=F3n wrote: > Well, I meant "the probability of your block being the hardest". > What a miner can do is hash the block (cheating the timestamp) for 2 > more minutes than the rest of the people and then send it to the other > nodes. Nodes cannot possibly know when did you hashed the block only > by looking at their clock when they receive it, because there's also > network latency. True enough; but then the same is true for everyone else. If the window is= 2=20 minutes after the stated time, then everyone _can_ wait until the end of th= at=20 window. However, they risk their block being rejected by their peers, and= =20 their efforts are wasted. In fact, it can be guaranteed by making the acce= pt=20 window zero. There is then no reason to carry on computing after the rewar= d=20 window closes, since you know your peers will reject it. > > (2) For the network clock; see util.cpp:GetAdjustedTime(). >=20 > 1) This is part of the satoshi client but not the protocol. A miner > can rewrite this part of the code and there won't be anything in the > chain that contradicts the protocol. Well yes. What does that matter? It's only a way of calculating an averag= e=20 time. The node can use any clock it wants, as long as the block time is=20 verified by the peers. > 2) I haven't read the code but I'm pretty sure that's not a perfect > decentralized clock. It definitely isn't. NTP is mentioned in the source as an alternative. > I will be more specific. Where's the network clock in the chain (in > the protocol)? It's nothing to do with the protocol; it's an individual miner choosing=20 whether to accept or reject a block based on the timestamp it claims, and t= he=20 current time as the miner sees it. For the sake of compatibility, the clie= nts=20 currently choose to use a community clock as "current", as established from= =20 the time they receive from peers in the "version" message (it actually hold= s=20 offsets between them, which is pretty bad, as a long-connected client will= =20 drift). They don't have to, but if miners aren't using time that approxima= tes=20 what their peers are using, under my system, their blocks would be rejected= :=20 so an incentive to use that "community clock" exists. Andy =2D-=20 Dr Andy Parkins andyparkins@gmail.com --nextPart2567792.LKsXHrLWy7 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) iEYEABECAAYFAk7NEWoACgkQwQJ9gE9xL20jwQCeKy6bb0lumBtQMtcngh8Jp72q nMYAnAuiWBaGAMVhZYwrOlkmgpOmiD3Q =HnOD -----END PGP SIGNATURE----- --nextPart2567792.LKsXHrLWy7--