Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 271CF92 for ; Wed, 21 Oct 2015 08:26:48 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ig0-f174.google.com (mail-ig0-f174.google.com [209.85.213.174]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id BDF03E4 for ; Wed, 21 Oct 2015 08:26:47 +0000 (UTC) Received: by igdg1 with SMTP id g1so81158133igd.1 for ; Wed, 21 Oct 2015 01:26:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=1Yd70tdsMyGvhYRYk9YcuyjlnqT6FEx3z3EqYXoQNKA=; b=V/zoUrqNwReIkqeE20/dviRHX22Fr7hmTrv4ZpfycMvudAPg4ItD2EWkflPPtTwEzN wH+5hNP32v05XMV5kxusAlYtDvGYi5SPQEpEoBgzzJTq3WIk8+09E8uDWURMjDxRkF8H jcs3XVN444ze6H8+LH/fyN2WSIAQGZ6xXrnmLL/6Xt4meUau9ytpfhCu6lfLWHFADUv9 YtbIH6MfgjXcoy/NuyUFv1RBPrgfo2QNioTWB0KJJ/f1BX7pfF+BdhInWiSZyaAt51Tc uYGF/ThCxss9qKStRPkZUvDz2urcuKvu1AN2qeCQy4XMB1jFeTRzpGPZScPatyNyrfS1 K9eA== MIME-Version: 1.0 X-Received: by 10.50.23.80 with SMTP id k16mr8957316igf.62.1445416007162; Wed, 21 Oct 2015 01:26:47 -0700 (PDT) Received: by 10.107.23.197 with HTTP; Wed, 21 Oct 2015 01:26:47 -0700 (PDT) In-Reply-To: References: <201510210618.56159.luke@dashjr.org> Date: Wed, 21 Oct 2015 08:26:47 +0000 Message-ID: From: Gregory Maxwell To: Luke Dashjr Content-Type: text/plain; charset=UTF-8 X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: Bitcoin Dev Subject: Re: [bitcoin-dev] [BIP] Normalized transaction IDs X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Oct 2015 08:26:48 -0000 On Wed, Oct 21, 2015 at 7:48 AM, Gregory Maxwell wrote: > I'm still sad that uniform segregated witeness is so hard to deploy, > adding another id to every utxo set won't be a nice cost. :( But I > have been trying for a long time to come up with anything better and > not being successful. Oh good. Luke solved it. To deploy SW without a disruptive flag day this encoding could be used: A new P2SH like scriptPubkey type is defined. In the soft-fork, the scriptsig for this scriptPubkey is required to be empty. Signatures are not covered under txid, but carried along side. Then committed to in blocks in a separate hashtree. The only disadvantage to the approach used in elements alpha that I can come up with so far (in the few minutes since luke turned my can't into a can) is that that the approach in EA did not disrupt the normal relay handling process, and this would, since relay that transports the extradata either needs to use a different hash that includes the witness, or have a separate mechanism for witness transport.