From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 6F4CF1189 for ; Fri, 11 Sep 2015 17:18:11 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ig0-f175.google.com (mail-ig0-f175.google.com [209.85.213.175]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 08B881CF for ; Fri, 11 Sep 2015 17:18:10 +0000 (UTC) Received: by igbkq10 with SMTP id kq10so49901921igb.0 for ; Fri, 11 Sep 2015 10:18:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=uKqFo67N+4vau0Enybsx+MiEGXQ1QH+I3y7giw/Uk3o=; b=hiPGXKX3ZTJGCccxEWC++fy5zP8OQyHwyPeoelGp9LwvgD8BG5iLL/eQ7o9R55WsWG qlrJOrnzUQ2HiR/jvuFTuKkrwLBp5vU8nxrtyxsn+CeV9nhn/o7pk0ttlLVMLqtom+bb YHZCFRhn1AWOkBhl93TQIwWk+iofEeC22bMqIE/Ff1hI8x/KxC2dJWaxGk/pXJ2IOLpw Px1jX67IyBFf+ajpgz8D6KEweIaPAo04HCAUFPzV52fBBBu38eLs0UtQhYHTlEeqrWkZ OBhtmRyMVcCHkKiREM3do/vqEa4tU4f8TgSOYddshYfKiq9JugzdB13VfEoeCxu11PH6 XlmQ== MIME-Version: 1.0 X-Received: by 10.50.79.196 with SMTP id l4mr17198351igx.48.1441991890445; Fri, 11 Sep 2015 10:18:10 -0700 (PDT) Received: by 10.36.110.19 with HTTP; Fri, 11 Sep 2015 10:18:10 -0700 (PDT) In-Reply-To: References: Date: Fri, 11 Sep 2015 13:18:10 -0400 Message-ID: From: Christophe Biocca To: =?UTF-8?B?Sm9yZ2UgVGltw7Nu?= Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: Bitcoin Dev Subject: Re: [bitcoin-dev] Bitcoin Days Destroyed as block selection heuristic X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 Sep 2015 17:18:11 -0000 It's pretty obvious that Dave is suggesting an alternate tie-breaker: > It also makes an empty block far less attractive because it is easily rep= laced, all the way until the next block locks it in. I do see a problem with the proposal. Right now, when a miner sees a new block with the most work and there are no ties, it is always a good idea to build on top of it (unless they're in the middle of building a private chain, or other pathological cases). With this new heuristic (assuming it is actually followed by a good chunk of people), a miner can reasonably know whether or not they can safely mine a sibling of the block instead. When enough widely propagated transactions exist, and the block to orphan is small, there's minimal risk in mining a sibling block instead of a child block (the only extra risk is in someone else mining a child block right around the time we suceed in mining a siblish block, where we'll definitely be orphaned instead of ~50% of the time). Because the risk can be measured and is sometimes very small, it will then be profitable for a miner to orphan a small non-empty block and double-spend some confirmed transactions whenever the block confirming them is easily replaced. This lowers the security of 1-conf transactions. Mind you, that risk doesn't apply if we prefer non-empty blocks to empty blocks and leave it at that, or only switch if the new block doesn't double spend transactions in the old one, so it's a fixable issue. On 11 September 2015 at 12:32, Jorge Tim=C3=B3n wrote: > > On Sep 11, 2015 12:27 PM, "Dave Scotese via bitcoin-dev" > wrote: >> >> Rather than (promising to, and when they don't actually, at least >> pretending to) use the first-seen block, I propose that a more sophistic= ated >> method of choosing which of two block solutions to accept. > > There's already a criterion to chose: the one with more work (in valid > blocks) on top of it. > > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >