Return-Path: Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id BD615C016E for ; Sun, 7 Jun 2020 00:40:59 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 8F5802035E for ; Sun, 7 Jun 2020 00:40:59 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 7rjH2iL2KiBO for ; Sun, 7 Jun 2020 00:40:57 +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 silver.osuosl.org (Postfix) with ESMTPS id 40C2420352 for ; Sun, 7 Jun 2020 00:40:57 +0000 (UTC) Date: Sun, 07 Jun 2020 00:40:51 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=protonmail; t=1591490454; bh=sYE1I+4rnrQVM8uOY1ZbYMEoYGSKy8NRVMTVY2X3E/Y=; h=Date:To:From:Reply-To:Subject:In-Reply-To:References:From; b=PySVjiERai8tR/h5p35TSGKpSvGV417vhthbfzIuqI2LCKSB4a4Mbmdx1LvC63fZT KGD26N7dw0V4Eov82YPaC9vVPWTYElZ8eRT9ZYR5kSIiE4WqZAeT8NkhH4p15Iv3aY SfpsWnuODPlZ/d8rGoiDWiXi1UCWDI3D6BLcwTmM= To: Mostafa Sedaghat joo , 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] Stamping transaction 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: Sun, 07 Jun 2020 00:40:59 -0000 Good morning Mostafa, First off, the proposed mechanism can be made into a softfork by using an u= nspendable `scriptPubKey` with 0 output value. For example, a stamp could by convention be any 0-value output whose `scrip= tPubKey` is ` OP_0`, which should be unspendable. Post-softfork nodes would reject blocks where some transaction is stamped a= nd the stamped `` is not within the last N blocks. Pre-softfork nodes would not see anything special about the unspendable `sc= riptPubKey` and would just accept it (but would not relay such transactions= due to standardness). Engineering-wise, block validation now needs to memorize the last N block h= ashes. The mempool design currently assumes that a transaction that enters the mem= pool is always valid unless any UTXOs it spends have been removed. This is important since miner block selection algorithms assume the mempool= contains transactions that are currently valid. Thus, there is the additional need to drop transactions from the mempool if= they are stamped with a block that has dropped from the stamp TTL. Another issue is incentives. The stamp takes up blockchain space that is paid for by the creator of the = transaction. Further, the creator of the transaction gains no advantage from the stamped= transaction; it is others who gain an advantage (the stamped transaction i= s more likely to be dropped from the mempool). Discounting the stamp somehow will probably make this into a hardfork. It might be sneaked into the witness somehow by adding it as a field somewh= ere in the new parts of Taproot (there is, a new block of data in Taproot t= hat can be used for this), but note that the cost will still be non-zero (a= nd users of this feature will still have a disadvantage in that their trans= actions are more likely to be dropped from the mempool). Finally, it is expected to increase bandwidth use since a dropped stamped t= ransaction will probably be rebroadcast with a new stamp, so effectively th= e transaction is retransmitted again with a different stamp. Regards, ZmnSCPxj