From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp2.osuosl.org (smtp2.osuosl.org [IPv6:2605:bc80:3010::133]) by lists.linuxfoundation.org (Postfix) with ESMTP id B625FC000E for ; Tue, 31 Aug 2021 14:22:45 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 9F6E34010D for ; Tue, 31 Aug 2021 14:22:45 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -0.199 X-Spam-Level: X-Spam-Status: No, score=-0.199 tagged_above=-999 required=5 tests=[BAYES_05=-0.5, 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_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: smtp2.osuosl.org (amavisd-new); dkim=pass (1024-bit key) header.d=protonmail.com Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id uFK4TuZlZfNp for ; Tue, 31 Aug 2021 14:22:41 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mail-40137.protonmail.ch (mail-40137.protonmail.ch [185.70.40.137]) by smtp2.osuosl.org (Postfix) with ESMTPS id 5E4FB400CC for ; Tue, 31 Aug 2021 14:22:41 +0000 (UTC) Date: Tue, 31 Aug 2021 14:22:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=protonmail; t=1630419758; bh=b1/a/fjAFMQE1SmNid0PyY2irnE2YTHQQCDmjyVJD3U=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=X5xCOZWX755tMx1K98Ux1Usc6hv2KNqSsXrFFgqAPF5PMcQ4KB+n5mTCU/2U85qad wYcrreqtkFCrdye9irzhkIbdvJLzM4f8NR7KOYQBelYt+m6oC6IxrDUD+cGH5VS08Z D4B4JeuYLubhvmG+7f6stYH/DF4UE4q1TIM6d4ws= To: Zac Greenwood From: ZmnSCPxj Reply-To: ZmnSCPxj Message-ID: In-Reply-To: References: <1qkQ1p1rAZApZhMKVFwQV6gfLyZxMYIUPrhcjtXNU4z0DBRwslPSbi76GnNnllpvPPfqt1bH3EyzJNhfK0Uxum7zJ_dh3H0DXqUpf2nmHyk=@protonmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Exploring: limiting transaction output amount as a function of total input value 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: Tue, 31 Aug 2021 14:22:45 -0000 Good morning Zac, > Hi ZmnSCPxj, > > Thank you for your helpful response. We're on the same page concerning pr= ivacy so I'll focus on that. I understand from your mail that privacy would= be reduced by this proposal because: > > * It requires the introduction of a new type of transaction that is diffe= rent from a "standard" transaction (would that be P2TR in the future?), red= ucing the anonymity set for everyone; > * The payment and change output will be identifiable because the change o= utput must be marked encumbered on-chain; > * The specifics of how the output is encumbered must be visible on-chain = as well reducing privacy even further. > > I don't have the technical skills to judge whether these issues can someh= ow be resolved. In functional terms, the output should be spendable in a wa= y that does not reveal that the output is encumbered, and produce a change = output that cannot be distinguished from a non-change output while still be= ing encumbered. Perhaps some clever MAST-fu could somehow help? I believe some of the covenant efforts may indeed have such clever MAST-fu = integrated into them, which is why I pointed you to them --- the people dev= eloping these (aj I think? RubenSomsen?) might be able to accommodate this = or some subset of the desired feature in a sufficiently clever covenant sch= eme. There are a number of such proposals, though, so I cannot really point you = to one that seems likely to have a lot of traction. Regards, ZmnSCPxj