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 62B7BD49 for ; Thu, 10 Sep 2015 17:18:55 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from s47.web-hosting.com (s47.web-hosting.com [199.188.200.16]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id BEB6926C for ; Thu, 10 Sep 2015 17:18:54 +0000 (UTC) Received: from localhost ([::1]:37634 helo=server47.web-hosting.com) by server47.web-hosting.com with esmtpa (Exim 4.85) (envelope-from ) id 1Za5Ur-002URR-1K for bitcoin-dev@lists.linuxfoundation.org; Thu, 10 Sep 2015 13:18:53 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 10 Sep 2015 13:18:52 -0400 From: jl2012@xbt.hk To: bitcoin-dev@lists.linuxfoundation.org Message-ID: <282c2912327370d30a0d341dcf1a6499@xbt.hk> X-Sender: jl2012@xbt.hk User-Agent: Roundcube Webmail/1.0.5 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - server47.web-hosting.com X-AntiAbuse: Original Domain - lists.linuxfoundation.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - xbt.hk X-Get-Message-Sender-Via: server47.web-hosting.com: authenticated_id: jl2012@xbt.hk X-Source: X-Source-Args: X-Source-Dir: X-From-Rewrite: unmodified, already matched X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,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 Subject: [bitcoin-dev] =?utf-8?q?MAST_with_OP=5FEVAL_and_OP=5FCAT?= 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, 10 Sep 2015 17:18:55 -0000 Inspired by Pieter's Tree Signatures, I believe Merkleized Abstract Syntax Trees (MAST) could be implemented with only OP_CAT and OP_EVAL (BIP12). The idea is very simple. Using a similar example in Pieter's paper, scriptSig = Z1 0 1 1 X6 1 K9 0 scriptPubKey = DUP HASH160 EQUALVERIFY EVAL serialized script = 8 PICK SHA256 (SWAP IF SWAP ENDIF CAT SHA256)*4 EQUALVERIFY EVAL This will run the 10-th sub-script, when there are 11 sub-scripts in the MAST I think this is the easiest way to enable MAST since the reference implementation for BIP12 is already there. We could enable OP_CAT only inside OP_EVAL so this will be a pure softfork. Ref: Tree Signatures: https://blockstream.com/2015/08/24/treesignatures/ BIP12: https://github.com/bitcoin/bips/blob/master/bip-0012.mediawiki