From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id E04B2C0001 for ; Mon, 1 Mar 2021 15:06:24 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id C7D5183D37 for ; Mon, 1 Mar 2021 15:06:24 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: 0.804 X-Spam-Level: X-Spam-Status: No, score=0.804 tagged_above=-999 required=5 tests=[BAYES_50=0.8, KHOP_HELO_FCRDNS=0.001, SPF_HELO_NONE=0.001, SPF_NONE=0.001, UNPARSEABLE_RELAY=0.001] autolearn=ham autolearn_force=no Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id HyuKWWnewPA0 for ; Mon, 1 Mar 2021 15:06:24 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from azure.erisian.com.au (cerulean.erisian.com.au [139.162.42.226]) by smtp1.osuosl.org (Postfix) with ESMTPS id CBF7E83365 for ; Mon, 1 Mar 2021 15:06:23 +0000 (UTC) Received: from aj@azure.erisian.com.au (helo=sapphire.erisian.com.au) by azure.erisian.com.au with esmtpsa (Exim 4.92 #3 (Debian)) id 1lGk7l-00010j-SZ for ; Tue, 02 Mar 2021 01:06:21 +1000 Received: by sapphire.erisian.com.au (sSMTP sendmail emulation); Tue, 02 Mar 2021 01:06:14 +1000 Date: Tue, 2 Mar 2021 01:06:14 +1000 From: Anthony Towns To: Bitcoin Protocol Discussion Message-ID: <20210301150614.vz557ssn2epxknjn@erisian.com.au> References: <202102281933.30691.luke@dashjr.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202102281933.30691.luke@dashjr.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Spam-Score-int: -18 X-Spam-Bar: - Subject: Re: [bitcoin-dev] LOT=False is dangerous and shouldn't be used X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 01 Mar 2021 15:06:25 -0000 On Sun, Feb 28, 2021 at 07:33:30PM +0000, Luke Dashjr via bitcoin-dev wrote: > As we saw in 2017 with BIP 9, coordinating activation by miner signal alone, > despite its potential benefits, also leaves open the door to a miner veto. To the contrary, we saw in 2017 that miners could *not* successfully veto a BIP 9 activation. It was certainly more effort and risk than was desirable to override the attempted veto, but the attempt at vetoing nevertheless failed. > It wouldn't be much different than adding back the inflation bug > (CVE-2018-17144) and trusting miners not to exploit it. That is ridiculous FUD. > With LOT=False in the picture, however, things can get messy: LOT=false is always in the picture if we are talking about a soft-fork: the defining feature of a soft-fork is that old node software continues to work, and old node software will be entirely indifferent to whether activation is signalled or not. > some users will > enforce Taproot(eg) (those running LOT=True), while others will not (those > with LOT=False) If you are following bip8 with lockinontimeout=false, you will enforce taproot rules if activation occurs, you will simply not reject blocks if activation does not occur. > Users with LOT=True will still get all the safety thereof, > but those with LOT=False will (in the event of miners deciding to produce a > chain split) face an unreliable chain, being replaced by the LOT=True chain > every time it overtakes the LOT=False chain in work. This assumes anyone mining the chain where taproot does not activate is not able to avoid a reorg, despite having majority hashpower (as implied by the lot=true chain having to overtake them repeatedly). That's absurd; avoiding a reorg is trivially achieved via running "invalidateblock", or via pool software examining block headers, or via a patch along the lines of MUST_SIGNAL enforcement, but doing the opposite. For concreteness, here's a sketch of such a patch: https://github.com/ajtowns/bitcoin/commit/f195688bd1eff3780f200e7a049e23b30ca4fe2f > For 2 weeks, users with LOT=False would not have a usable network. That's also ridiculous FUD. If it were true, it would mean the activation mechanism was not acceptable, as non-upgraded nodes would also not have a usable network for the same reason. Fortunately, it's not true. More generally, if miners are willing to lose significant amounts of money mining orphan blocks, they can do that at any time. If they're not inclined to do so, it's incredibly straightforward for them to avoid doing so, whatever a minority of other miners might do. > The overall risk is maximally reduced by LOT=True being the only deployed > parameter, and any introduction of LOT=False only increases risk probability > and severity. LOT=false is the default behaviour of everything single piece of node software out there. That behaviour doesn't need to be introduced, it's already universal. Cheers, aj