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 35967C4D for ; Thu, 17 Dec 2015 17:55:48 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from azure.erisian.com.au (cerulean.erisian.com.au [106.187.51.212]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id C757411D for ; Thu, 17 Dec 2015 17:55:47 +0000 (UTC) Received: from aj@azure.erisian.com.au (helo=sapphire.erisian.com.au) by azure.erisian.com.au with esmtpsa (Exim 4.84 #2 (Debian)) id 1a9cmH-0001aQ-7Y for ; Fri, 18 Dec 2015 03:55:46 +1000 Received: by sapphire.erisian.com.au (sSMTP sendmail emulation); Fri, 18 Dec 2015 03:55:41 +1000 Date: Fri, 18 Dec 2015 03:55:41 +1000 From: Anthony Towns To: bitcoin-dev@lists.linuxfoundation.org Message-ID: <20151217175541.GA10809@sapphire.erisian.com.au> References: <49257841-66C8-4EF7-980B-73DC604CA591@mattcorallo.com> <9869fe48a4fc53fc355a35cead73fca2@xbt.hk> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY 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] Segregated Witness in the context of Scaling Bitcoin 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: Thu, 17 Dec 2015 17:55:48 -0000 On Thu, Dec 17, 2015 at 04:51:19PM +0100, sickpig--- via bitcoin-dev wrote: > On Thu, Dec 17, 2015 at 2:09 PM, Jorge Timón wrote: > > Unless I'm missing something, 2 mb x4 = 8mb, so bip102 + SW is already > > equivalent to the 2-4-8 "compromise" proposal [...] > isn't SegWit gain ~75%? hence 2mb x 1.75 = 3.5. Segwit as proposed gives a 75% *discount* to witness data with the same limit, so at a 1MB limit, that might give you (eg) 2.05MB made up of 650kB of base block data plus 1.4MB of witness data; where 650kB + 1.4MB/4 = 1MB at the 1MB limit; or 4.1MB made up of 1.3MB of base plus 2.8MB of witness, for 1.3MB+2.8MB/4 = 2MB at a 2MB limit. > 4x is theoric gain you get in case of 2-2 multisig txs. With segregated witness, 2-2 multisig transactions are made up of 94B of base data, plus about 214B of witness data; discounting the witness data by 75% gives 94+214/4=148 bytes. That compares to about 301B for a 2-2 multisig transaction with P2SH rather than segwit, and 301/148 gives about a 2.03x gain, not a 4x gain. A 2.05x gain is what I assumed to get the numbers above. You get further improvements with, eg, 3-of-3 multisig, but to get the full, theoretical 4x gain you'd need a fairly degenerate looking transaction. Pay to public key hash with segwit lets you move about half the transaction data into the witness, giving about a 1.6x improvement by my count (eg 1.6MB = 800kB of base data plus 800kB of witness data, where 800kB+800kB/4=1MB), so I think a gain of between 1.6 and 2.0 is a reasonable expectation to have for the proposed segwit scheme overall. Cheers, aj