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 0A5AE2640 for ; Mon, 11 Feb 2019 04:29:52 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-40130.protonmail.ch (mail-40130.protonmail.ch [185.70.40.130]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 2622125A for ; Mon, 11 Feb 2019 04:29:51 +0000 (UTC) Date: Mon, 11 Feb 2019 04:29:42 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=default; t=1549859389; bh=dA1vkhY6Ho/stxjFaucq4QycKLAYQEif5/TSgzTw2cE=; h=Date:To:From:Reply-To:Subject:In-Reply-To:References:Feedback-ID: From; b=o2lomqoJXN/KlhZcRfbMZqQXENZsLgZKeQv6BFTurU27Ce69Wou29y/dazPGlehZL DQj3HS1zC557eQFbcgkRkkBDmiiSB2a6UfEDWNsfeJW2K0Zx3r/uHCZOXc4AO1g74P RD11HAnvP8gf11VOREfrKkJRNfsh0Ba4KRuL0Fl4= To: "Kenshiro \\[\\]" , Bitcoin Protocol Discussion From: ZmnSCPxj Reply-To: ZmnSCPxj Message-ID: In-Reply-To: References: Feedback-ID: el4j0RWPRERue64lIQeq9Y2FP-mdB86tFqjmrJyEPR9VAtMovPEo9tvgA0CrTsSHJeeyPXqnoAu6DN-R04uJUg==:Ext:ProtonMail MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-2.2 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, FROM_LOCAL_NOVOWEL, 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 X-Mailman-Approved-At: Tue, 12 Feb 2019 12:46:40 +0000 Subject: Re: [bitcoin-dev] Implementing Confidential Transactions in extension blocks X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 11 Feb 2019 04:29:53 -0000 Good morning Kenshiro, > - Soft fork: old nodes see CT transactions as "sendtoany" transactions There is a position that fullnodes must be able to get a view of the UTXO s= et, and extension blocks (which are invisible to pre-extension-block fullno= des) means that fullnodes no longer have an accurate view of the UTXO set. SegWit still provides pre-SegWit fullnodes with a view of the UTXO set, alt= hough pre-SegWit fullnodes could be convinced that a particular UTXO is any= one-can-spend even though they are no longer anyone-can-spend. Under this point-of-view, then, extension block is "not" soft fork. It is "evil" soft fork since older nodes are forced to upgrade as their int= ended functionality becomes impossible. In this point-of-view, it is no better than a hard fork, which at least is = very noisy about how older fullnode versions will simply stop working. > - Safe: if there is a software bug in CT it's impossible to create new co= ins because the coins move from normal block to normal block as public tran= sactions I think more relevant here is the issue of a future quantum computing breac= h of the algorithms used to implement confidentiality. I believe this is also achievable with a non-extension-block approach by im= plementing a globally-verified publicly-visible counter of the total amount= in all confidential transaction outputs. Then it becomes impossible to move from confidential to public transactions= with a value more than this counter, thus preventing inflation even if a f= uture QC breach allows confidential transaction value commitments to be ope= ned to any value. (do note that a non-extension-block approach is a definite hardfork) > - Capacity increase: the CT signature is stored in the extension block, s= o CT transactions increase the maximum number of transactions per block This is not an unalloyed positive: block size increase, even via extension = block, translates to greater network capacity usage globally on all fullnod= es. Regards, ZmnSCPxj