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 F031CE51 for ; Thu, 24 May 2018 02:08:09 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ua0-f176.google.com (mail-ua0-f176.google.com [209.85.217.176]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 9C517180 for ; Thu, 24 May 2018 02:08:08 +0000 (UTC) Received: by mail-ua0-f176.google.com with SMTP id e8-v6so34694uam.13 for ; Wed, 23 May 2018 19:08:08 -0700 (PDT) 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=81BylAftLRxQSXG/PFKDVugGfqmDcC7Kotzo3Mz130I=; b=Ig5f6icns4QtXQyLSGhwKi2AL6JKgnarRGPAo1ls5Ci4m1GJ5iGBWo+YF+n8dY0HmQ CxpVCahWJuqbVXKgmnB6Q4E8eDl9JXtX9qkwIoYPL8B7RV6SN4ImgMcKSq7hgooalaq1 zb7lxOCCyZxy/DSfKkR7EnesuqsThySInmpOBHbqik2UZcfabDLP/dMWZjqYAqCqO9aF huDxBL/h5hJdJf2LSkg9STQddfI+NB8O7XRMqnYmM2N2DfGaAAceSS3SyvKZNjqKoz0a K3Bcj8NHiaPeRbDYpSPlHoF5FFZhPMQsV3oj04vBE7687HW7hAZvKZcb+V2TEGY7kI1O 52kw== 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=81BylAftLRxQSXG/PFKDVugGfqmDcC7Kotzo3Mz130I=; b=GoWcwGzuGC1RRMdcohkvSJqT0nYRbaoTORyARw6d5J1rbdhgvTszHOrvxbxGr3ovMg ie2q3lQ1pXS7GXrVRQzI8CwOtDK9sAHh+KfF9fBuKrQG8bTFhx+XjehiplW6kvZBfQX7 pGUxhEauwmOz/TYDFAV4/jMDWBRESkE8lnIBqeyD500AMqdRWFadwU0Ikds8QQrkRCCB /czo3qtVYY+HRczsvHX21FGzIsSNNDZhRZn2GbJoSru3FTwp4jQcxSngk8Tw/MsciauX pxw557//z/Ii+h4reZ6+oMpHhyRY2BZHvU4gDgZGGDnPN6HclejDZh//uM4TKKLlvhI0 t2Bg== X-Gm-Message-State: ALKqPwcqLArS3rcjROG6TWkombrlN2WtHLzlnw8lUmd72/Xd+595hRlR /EZvj8gRql+7zkSb/z4sPzIuSnwlMymeavk9KRM= X-Google-Smtp-Source: AB8JxZpc0yGQYGT/r/wgmhlS9xVxKjzUSPiQwJdXUhXGoWcibVZ+A3mAx9ixRULLyijHC96UmM8vKXXue9NyswctxHQ= X-Received: by 2002:ab0:1c16:: with SMTP id a22-v6mr3664105uaj.27.1527127687658; Wed, 23 May 2018 19:08:07 -0700 (PDT) MIME-Version: 1.0 Sender: gmaxwell@gmail.com Received: by 2002:a67:5184:0:0:0:0:0 with HTTP; Wed, 23 May 2018 19:08:07 -0700 (PDT) In-Reply-To: References: From: Gregory Maxwell Date: Thu, 24 May 2018 02:08:07 +0000 X-Google-Sender-Auth: _08qmLWwEIN9SElsoAkQOcT6iGM Message-ID: To: Pieter Wuille , 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] Should Graftroot be optional? 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: Thu, 24 May 2018 02:08:10 -0000 On Thu, May 24, 2018 at 1:58 AM, Pieter Wuille via bitcoin-dev wrote: > Thanks everyone who commented so far, but let me clarify the context > of this question first a bit more to avoid getting into the weeds too > much. My understanding of the question is this: Are there any useful applications which would be impeded if a signing party who could authorize an arbitrary transaction spending a coin had the option to instead sign a delegation to a new script? The reason this question is interesting to ask is because the obvious answer is "no": since the signer(s) could have signed an arbitrary transaction instead, being able to delegate is strictly less powerful. Moreover, absent graftroot they could always "delegate" non-atomically by spending the coin with the output being the delegated script that they would have graftrooted instead. Sometimes obvious answers have non-obvious counter examples, e.g. Andrews points related to blindsigning are worth keeping in mind.