From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1R3qia-0000k7-TP for bitcoin-development@lists.sourceforge.net; Wed, 14 Sep 2011 14:45:40 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.161.47 as permitted sender) client-ip=209.85.161.47; envelope-from=gavinandresen@gmail.com; helo=mail-fx0-f47.google.com; Received: from mail-fx0-f47.google.com ([209.85.161.47]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1R3qiX-00086j-76 for bitcoin-development@lists.sourceforge.net; Wed, 14 Sep 2011 14:45:40 +0000 Received: by mail-fx0-f47.google.com with SMTP id 1so2401181fxi.34 for ; Wed, 14 Sep 2011 07:45:36 -0700 (PDT) MIME-Version: 1.0 Received: by 10.223.33.19 with SMTP id f19mr60024fad.122.1316011536772; Wed, 14 Sep 2011 07:45:36 -0700 (PDT) Received: by 10.152.25.105 with HTTP; Wed, 14 Sep 2011 07:45:36 -0700 (PDT) In-Reply-To: <4E6F83C3.9020108@jerviss.org> References: <4E6F83C3.9020108@jerviss.org> Date: Wed, 14 Sep 2011 10:45:36 -0400 Message-ID: From: Gavin Andresen To: kjj Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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 (gavinandresen[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: 1R3qiX-00086j-76 Cc: bitcoin-development@lists.sourceforge.net Subject: Re: [Bitcoin-development] Difficulty adjustment / time issues 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, 14 Sep 2011 14:45:41 -0000 > But that doesn't solve the whole problem, because the block timestamp > checking is based on the assumption that the node is looking at the bitco= in > clock rather than the, ahem, real clock. =A0If we change the idea of netw= ork > time to NTP, we will then need to write (and test!) new block timestamp > rules to account for the new assumptions. Why? The block timestamp rules currently give HOURS of wiggle-room for timestamps. We can't change those rules without risking a chain split. Here's a thumbnail sketch of what I'm thinking: When new tip-of-chain blocks are received, IF their timestamp is unreasonable with respect to system time and the previous block's timestamp, then add them to a 'discouraged' list. (but follow the current rules for outright rejecting blocks based on timestamps too far in the future or past) Modify the getwork code to build on the second-from-tip block if the first-on-tip block is on the discouraged list. Assuming a majority of pools/miners adopt the "discourage blocks with stale timestamps" rule, that should squash any incentive for cartels to try to start playing with difficulty-- you would have to have 50+% power to start, or you risk producing mostly orphan blocks. > Also, this is going to cause problems for at least one pool operator. I'll trade more security for "make at least one pool operator have to do some work" any day. --=20 -- Gavin Andresen