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 A289ED69 for ; Mon, 13 Aug 2018 18:56:55 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-oi0-f44.google.com (mail-oi0-f44.google.com [209.85.218.44]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 5DC3578B for ; Mon, 13 Aug 2018 18:56:55 +0000 (UTC) Received: by mail-oi0-f44.google.com with SMTP id q11-v6so29100225oic.12 for ; Mon, 13 Aug 2018 11:56:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to; bh=gF0ZFJtBBBBdGId4IhM5L+Ba4Xy55jjDe+s+h+nL1LY=; b=MZPWYzwsQ15qL5gE/GgMgxObkCCO9/FnE1nNyRoF0aCLghbcNtF2S4kZSxUch+NlbL F7G8NpL3kZSHZMd4llWn2xkptteNJ6F3rAC+kuTfYJnN3EcPGJ7O6cFmlYmJexx98Pou 7/9mBb3pysLrMrTSHJ81k5/p3M1w2hRMEk0g9EifO7FK20xuyJkEbP/aQpJH9WAz+PMN vM1Q5KQrMKjepOWgNzASWaE/HCIc+IqDNkGPZxbuC7oYXQN+d9gqZWA0r8C65zabNzYF 3iTbjk3CweKbPosx+uW3qreL0j6G/L5BzRpaGkk+1W4Ef/yw/6RLKI20GE8/0LQztxrc BTJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=gF0ZFJtBBBBdGId4IhM5L+Ba4Xy55jjDe+s+h+nL1LY=; b=M/PrDMYhWiHqABsrGOBxtnIZ7Rw2qYFyfSydqu7ZN5bDl1WqQ1vujEUKa1izI7gAw/ 3Pqq3l2gxod8vxv5YWlBFxMMD5uCqxIR0OUNLYtpSrYHgzMEueYzeewH3wNijtND5kDR POVTI6aXoL4Y1YOzmd3OcmnFsCjznM1HExwKV3+K451A0bvQCNXceIXE++VcoMSuntPg PVYe/CKhauyoVAExf/hNbQs1vVjBR2o+c8dxUFI55P6Mou1clWAjxv77RlsL5fT0hgAL EGrmF7mzfmpLK55883fPLof/gnOYY4WKrWxlS4mOK/tdgdPP2JB3EOG3c8RtSq4Op/FJ JQHg== X-Gm-Message-State: AOUpUlGva/jK2sOGL3O+/H59jX8/i3fRRTrhKDW83PRGA9FunIjRPGmU Wsvinl+/yK8pn42wIZwQai0JTrm11Qd9e4LDvUnaKh6J X-Google-Smtp-Source: AA+uWPwmehJ0bJD1L1bgny2pQS/Q3oTTsoZ0Bw7tTZ1pL5ry0H/oJ9Cw87XyfydNuxfDDct6c4Co/8k++4qwhQreU8A= X-Received: by 2002:aca:3507:: with SMTP id c7-v6mr20521027oia.46.1534186614308; Mon, 13 Aug 2018 11:56:54 -0700 (PDT) MIME-Version: 1.0 From: Pieter Wuille Date: Mon, 13 Aug 2018 11:56:41 -0700 Message-ID: To: Bitcoin Dev Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: [bitcoin-dev] Witness serialization in PSBT non-witness UTXOs 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, 13 Aug 2018 18:56:55 -0000 Hello all, BIP174 currently specifies that non-witness UTXOs (the transactions being spent by non-witness inputs) should be serialized in network format. I believe there are two issues with this. 1. Even in case the transaction whose output being spent itself has a witness, this witness is immaterial to PSBT. It's only there to be able to verify the txid commits to the output/amount being spent, which can be done without witness. 2. "Network format" is a bit ambiguous. We can imagine a future softfork that introduces a new type of witness. Network format could be interpreted as including that new witness type, which is clearly unnecessary (by the above argument), and would gratuitously break compatibility with existing signers if implemented pedantically. So my suggestion is to update the specification to state that non-witness UTXOs must be serialized without witness. If it's too late for that, it should instead be updated to explicitly specify with or witnout witness, but it's safe to drop the witness. Opinions? Cheers, -- Pieter