From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id A7068C013B for ; Wed, 9 Dec 2020 22:33:04 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 95CB48756C for ; Wed, 9 Dec 2020 22:33:04 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id UQr7-qmTed8J for ; Wed, 9 Dec 2020 22:33:02 +0000 (UTC) X-Greylist: delayed 00:07:09 by SQLgrey-1.7.6 Received: from mail-41103.protonmail.ch (mail-41103.protonmail.ch [185.70.41.103]) by whitealder.osuosl.org (Postfix) with ESMTPS id 60ADA8737C for ; Wed, 9 Dec 2020 22:33:02 +0000 (UTC) Received: from mail-02.mail-europe.com (mail-02.mail-europe.com [51.89.119.103]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by mail-41103.protonmail.ch (Postfix) with ESMTPS id 1A3632002C6E for ; Wed, 9 Dec 2020 22:25:50 +0000 (UTC) Authentication-Results: mail-41103.protonmail.ch; dkim=pass (2048-bit key) header.d=achow101.com header.i=@achow101.com header.b="b/u7ML0V" Date: Wed, 09 Dec 2020 22:25:37 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=achow101.com; s=protonmail2; t=1607552740; bh=ds8SPtlXjOwf2uVYhcu0ZDm4N6hVwprzAuFnn4TcyJw=; h=Date:To:From:Reply-To:Subject:From; b=b/u7ML0VWIgM3noMpvteBlBDFNdyvgCqZeRSI6IE0PnryPBwZh3jTL46drZ2OM+Ks 3WWwn3w9NwJi8obQPfg4m92ft5q/HVk15eYXJuayKDUoKoChs14xRPwmMKij1wxmPF 4JW43DuSQrhppvHsVlyhRkAv+UR5+IrqczNOAkHOmRdKWfjF4OQy5fSFcmfzQXVz5y JRcdL/yo2hJYhZGK43G2avhzMrLsVk57TGHTaI2RPR0SLPG0XbNYhBAcJtb+yyQJzI 91xBEAIiWVttBHYbXhzPmEqdtxTQvytyVF+5yz7XYOAbvwVrauuWbhfaa3QKrlOaq8 pAqMINOKRcNGA== To: Bitcoin Protocol Discussion From: Andrew Chow Reply-To: Andrew Chow Message-ID: <1dd8c285-e3f4-4f03-d608-103a5026146d@achow101.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: [bitcoin-dev] New PSBT version proposal 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: Wed, 09 Dec 2020 22:33:04 -0000 Hi All, I would like to propose a new PSBT version that addresses a few=20 deficiencies in the current PSBT v0. As this will be backwards=20 incompatible, a new PSBT version will be used, v1. The primary change is to truly have all input and output data for each=20 in their respective maps. Instead of having to parse an unsigned=20 transaction and lookup some data from there, and other data from the=20 correct map, all of the data for an input will be contained in its map.=20 Doing so also disallows PSBT_GLOBAL_UNSIGNED_TX in this new version.=20 Thus I propose that the following fields be added: Global: * PSBT_GLOBAL_TX_VERSION =3D 0x02 =C2=A0 * Key: empty =C2=A0 * Value: 32-bit little endian unsigned integer for the transaction= =20 version number. Must be provided in PSBT v1 and omitted in v0. * PSBT_GLOBAL_PREFERRED_LOCKTIME =3D 0x03 =C2=A0 * Key: empty =C2=A0 * Value: 32 bit little endian unsigned integer for the preferred=20 transaction lock time. Must be omitted in PSBT v0. May be provided in=20 PSBT v1, assumed to be 0 if not provided. * PSBT_GLOBAL_INPUT_COUNT =3D 0x04 =C2=A0 * Key: empty =C2=A0 * Value: Compact size unsigned integer. Number of inputs in this=20 PSBT. Must be provided in PSBT v1 and omitted in v0. * PSBT_GLOBAL_OUTPUT_COUNT =3D 0x05 =C2=A0 * Key: empty =C2=A0 * Value: Compact size unsigned integer. Number of outputs in this= =20 PSBT. Must be provided in PSBT v1 and omitted in v0. Input: * PSBT_IN_PREVIOUS_TXID =3D 0x0e =C2=A0 * Key: empty =C2=A0 * Value: 32 byte txid of the previous transaction whose output at= =20 PSBT_IN_OUTPUT_INDEX is being spent. Must be provided in PSBT v1 and=20 omitted in v0. * PSBT_IN_OUTPUT_INDEX =3D 0x0f =C2=A0 * Key: empty =C2=A0 * Value: 32 bit little endian integer for the index of the output= =20 being spent. Must be provided in PSBT v1 and omitted in v0. * PSBT_IN_SEQUENCE =3D 0x0f =C2=A0 * Key: empty =C2=A0 * Value: 32 bit unsigned little endian integer for the sequence=20 number. Must be omitted in PSBT v0. May be provided in PSBT v1 assumed=20 to be max sequence (0xffffffff) if not provided. * PSBT_IN_REQUIRED_LOCKTIME =3D 0x10 =C2=A0 * Key: empty =C2=A0 * Value: 32 bit unsigned little endian integer for the lock time th= at=20 this input requires. Must be omitted in PSBT v0. May be provided in PSBT=20 v1, assumed to be 0 if not provided. Output: * PSBT_OUT_VALUE =3D 0x03 =C2=A0 * Key: empty =C2=A0 * Value: 64-bit unsigned little endian integer for the output's=20 amount in satoshis. Must be provided in PSBT v1 and omitted in v0. * PSBT_OUT_OUTPUT_SCRIPT =3D 0x04 =C2=A0 * Key: empty =C2=A0 * Value: The script for this output. Otherwise known as the=20 scriptPubKey. Must be provided in PSBT v1 and omitted in v0. This change allows for PSBT to be used in the construction of=20 transactions. With these new fields, inputs and outputs can be added as=20 needed. One caveat is that there is no longer a unique transaction=20 identifier so more care must be taken when combining PSBTs.=20 Additionally, adding new inputs and outputs must be done such that=20 signatures are not invalidated. This may be harder to specify. An important thing to note in this proposal are the fields=20 PSBT_GLOBAL_PREFERRED_LOCKTIME and PSBT_IN_REQUIRED_LOCKTIME. A Bitcoin=20 transaction only has a single locktime yet a PSBT may have multiple=20 locktimes. To choose the locktime for the transaction, finalizers must=20 choose the maximum of all of the *_LOCKTIME fields.=20 PSBT_IN_REQUIRED_LOCKTIME is added because some inputs, such as those=20 involving OP_CHECKLOCKTIMEVERIFY, require a specific minimum locktime to=20 be set. This field allows finalizers to choose a locktime that is high=20 enough for all inputs without needing to understand the scripts=20 involved. The PSBT_GLOBAL_PREFERRED_LOCKTIME is the locktime to use if=20 no inputs require a particular locktime. As these changes disallow the PSBT_GLOBAL_UNSIGNED_TX field, PSBT v1=20 needs the version number bump to enforce backwards incompatibility.=20 However once the inputs and outputs of a PSBT are decided, a PSBT could=20 be "downgraded" back to v0 by creating the unsigned transaction from the=20 above fields, and then dropping these new fields. If the list finds that these changes are reasonable, I will write a PR=20 to modify BIP 174 to incorporate them. Thanks, Andrew Chow