From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5A9EDC000A for ; Fri, 16 Apr 2021 23:53:02 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 42019606CA for ; Fri, 16 Apr 2021 23:53:02 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -0.4 X-Spam-Level: X-Spam-Status: No, score=-0.4 tagged_above=-999 required=5 tests=[BAYES_40=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, FROM_LOCAL_NOVOWEL=0.5, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no Authentication-Results: smtp3.osuosl.org (amavisd-new); dkim=pass (1024-bit key) header.d=protonmail.com Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id dDs76fQVZEfn for ; Fri, 16 Apr 2021 23:52:59 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mail-40130.protonmail.ch (mail-40130.protonmail.ch [185.70.40.130]) by smtp3.osuosl.org (Postfix) with ESMTPS id E60B960688 for ; Fri, 16 Apr 2021 23:52:58 +0000 (UTC) Date: Fri, 16 Apr 2021 23:52:48 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=protonmail; t=1618617175; bh=P6+WKPZi0FntUx3vSuYdP6pPu0nHA+Y49I6wT2EbRJw=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=i5yGofgGk8dvPUfSL5jNL2rkgaNPISgyuZ3cvK5OaImuSASIlT9GTkYG7HPHGmFV2 F3Jy+Yo04kquElp7PKTJ6L6QxNBXNS4U0jc7FRCVXYt6xZulc7p9lmGM2Kt6Fh64Ls TF9sRGFx61BZ8hIN0GqAYGxvcokDiT9aPig3pJLE= To: Christopher Gilliard , Bitcoin Protocol Discussion From: ZmnSCPxj Reply-To: ZmnSCPxj Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [bitcoin-dev] BIP - limiting OP_RETURN / HF 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: Fri, 16 Apr 2021 23:53:02 -0000 Good morning Christopher, > >> But more importantly, adding limitations on OP_RETURN transactions is = not helpful.=C2=A0 Users who want to embed arbitrary data in their transact= ions can always do so by encoding their data inside the values of legacy mu= lti-signature scriptpubkeys (pubkeys can be generated without knowing the p= rivate key in order to encode non-key related data).=C2=A0 Not only can use= rs do this, users have done this in the past.=C2=A0 However, this behaviour= is problematic because such multi-signature "data" scriptpubkeys are indis= tinguishable from "real" multisignature scriptpubkeys, and thus must be kep= t in the UTXO set.=C2=A0 This differs from outputs using OP_RETURN which ar= e provably unspendable, and therefore can be safely omitted from the UTXO s= et. > > This sounds like a good justification to remove the legacy multi-signatur= e capabilities as well. The same technique can be used on P2PKH as well --- the "pubkey hash" need = not be a hash of a public key, it can be a 20-byte commitment, or even an A= SCII message like "ZmnSCPxj is the best" (20 characters, I counted). There is nothing that *can* check if the hash of a public key is indeed the= hash of a public key unless you actually reveal the public key. If you need a 32-byte commitment, a P2WSH would work --- again the "script = hash" need not be a hash of a script, it can be any 32-byte commitment. In all these cases you have to waste 547 satoshi, but that tends to be smal= l compared to tx fees currently. Regards, ZmnSCPxj