Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 8E763D10 for ; Mon, 20 Nov 2017 18:59:36 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ua0-f175.google.com (mail-ua0-f175.google.com [209.85.217.175]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 17ECE522 for ; Mon, 20 Nov 2017 18:59:36 +0000 (UTC) Received: by mail-ua0-f175.google.com with SMTP id l25so6589849uag.8 for ; Mon, 20 Nov 2017 10:59:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to; bh=dETqQMWa88xJLdh9kmbSaQqRyUji7SdVA/c0AT4Z6G8=; b=uafc0cUIFPHGIRckTJA8obdV8bxFFlS1zUrof+BsptszsOrYTLMDgGazYr56U2WY5x 0ZVHHAjUZvHI2lGwTxtV7IMTNzrKkJ5TMB6Hc+6bpa/6hfGL40qqDSSRDr/OTLxvTOhs 1RFgnWX6DEwW3AiqKgNDWBonF2kSA1loQRfWk0dP+4blJ9zKybRAl9hwsmeB9wldTWH8 3w1YaByT4ub0oswatA5checQR94nIXYdBNpbcksDNq5AYqOLevOM52TgS2OfNf1ZeUnU 5qOLNb2s8kQqlOMdWGCzGGHmx0MqennlLceUnbYCsbRXL9Hl6Z80nEiFqBwXJ5hXO/8E 3aUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to; bh=dETqQMWa88xJLdh9kmbSaQqRyUji7SdVA/c0AT4Z6G8=; b=BceagRLS/qGSBiMtVhpjucDJ/ugf/nI1/byeEAVgKmQmwNIndOduHnFJMSCRPVS/ce mFULr5lbLYoOWbF0EnmiEgZZCfsfQrOUX2U6EwJVtV2DDQOFTbsu+zmfKoQ/wNQlgqc+ 9oWcqHxhoqHwOH5NxTLITCwtMhkKUiZ1FhHNeyUJWrQplI//AOhAs3B1FPI1F5X8u2ZH 6B67JVD7VMo8FJJHO5DLku33T341QUN9QY4elELFbUA/a5OZCODRjaK1RNMxnMN4xpJw K3jdNcrNFe6RMuqag495PKet4Bg/yEFCE/AnAo7XAKVjZ1QKGuDLKbEbyU9cnGUitWZ6 WmCQ== X-Gm-Message-State: AJaThX6dLVJVcliaiPXIl3DmqMn0xPlehujSn2R5EcZYaA6L5Oa7S74F f6axUZiTuZAROl2AxtlSZjGIG+D45xvK8mZtKog= X-Google-Smtp-Source: AGs4zMaaBr3iz5udIL2+w25KP6y/v+x9UgaJ6+es6Ft9HaiLDz2TvUc3OTZK0gn6NM86j3zlbvbkByuAIn8vytLx8jM= X-Received: by 10.159.32.135 with SMTP id 7mr12984582uaa.61.1511204375284; Mon, 20 Nov 2017 10:59:35 -0800 (PST) MIME-Version: 1.0 Sender: gmaxwell@gmail.com Received: by 10.103.85.148 with HTTP; Mon, 20 Nov 2017 10:59:34 -0800 (PST) In-Reply-To: References: From: Gregory Maxwell Date: Mon, 20 Nov 2017 18:59:34 +0000 X-Google-Sender-Auth: ZWqvv3k-biPEjV0bBpu-b7bJDcY Message-ID: To: Praveen Baratam , Bitcoin Protocol Discussion Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, 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: Re: [bitcoin-dev] Why SegWit Anyway? 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, 20 Nov 2017 18:59:36 -0000 On Mon, Nov 20, 2017 at 5:24 PM, Praveen Baratam via bitcoin-dev wrote: > Bitcoin Noob here. Please forgive my ignorance. > > From what I understand, in SegWit, the transaction needs to be serialized > into a data structure that is different from the current one where > signatures are separated from the rest of the transaction data. > > Why change the format at all? Why cant we just compute the Transaction ID > the same way the hash for signing the transaction is computed? That is effectively what segwit does, upto engineering minutia and compatibility details. Segwit does not serialize transactions in to a data structure where signatures are separated from the rest of the transaction data; this is a misunderstanding. The "segregated" refers to them being excluded from the TXID. The serialization of segwit on the p2p network in transactions and in blocks encodes the witness field inside the transactions, immediately prior to the nlocktime field.