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[73.241.30.225]) by smtp.gmail.com with ESMTPSA id d7sm1238712pgf.20.2017.10.01.13.39.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 01 Oct 2017 13:39:13 -0700 (PDT) Content-Type: text/plain; charset=gb2312 Mime-Version: 1.0 (1.0) From: Mark Friedenbach X-Mailer: iPhone Mail (15A402) In-Reply-To: Date: Sun, 1 Oct 2017 13:39:11 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: References: <201710010113.30518.luke@dashjr.org> <5A220A8D-3A85-49D0-8DB2-6BDEC362EAEB@friedenbach.org> <201710010247.42180.luke@dashjr.org> <460EDF1F-2BFD-4DBE-A921-73469C2EA9B9@friedenbach.org> To: Russell O'Connor X-Spam-Status: No, score=0.5 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, MIME_QP_LONG_LINE, RCVD_IN_DNSWL_NONE, RCVD_IN_SORBS_SPAM autolearn=disabled version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Version 1 witness programs (first draft) 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: Sun, 01 Oct 2017 20:39:16 -0000 > On Oct 1, 2017, at 12:41 PM, Russell O'Connor wr= ote: >=20 > Creating a Bitcoin script that does not allow malleability is difficult an= d requires wasting a lot of bytes to do so, typically when handling issues a= round non-0-or-1 witness values being used with OP_IF, and dealing with non-= standard-zero values, etc. Script validation flags of the correct place to do this. We already have pol= icy validation flags that check for these things. They were not made consens= us rules with Segwit v0 mainly due to concern over scope creep in an already= large overhaul, of my memory is correct. Script versions and quadratic hash= ing fixes where the minimum necessary to allow segwit to activate safely whi= le still enabling future upgrades that would otherwise have been hard forks.= We knew that we would be later changing the EC signature scheme to be somet= hing that supported signature aggregation, and that would be more appropriat= e time to discuss such changes. As we are considering to do now (although wi= tness versions means we don=A1=AFt need to omnibus the script upgrade here e= ither, so a v1 before signature aggregation is ready is fine IMHO). In any case if there is any general witness malleability due to opcode seman= tics that it=A1=AFs not fixed by one of our existing policy flags, that is a= bug and I would encourage you to report it. > I'll argue that I don't want my counter-party going off and using a very d= eeply nested key in order to subvert the fee rate we've agreed upon after I'= ve signed my part of the input. If we are doing multi-party signing of inpu= ts we need to communicate anyways to construct the transaction. I see no pr= oblem with requiring my counter-party to choose their keys before I sign so t= hat I know up front what our fee rate is going to be. If they lose their ke= ys and need a backup, they should have to come back to me to resign in order= that we can negotiate a new fee rate for the transaction and who is going t= o be covering how much of the fee and on which inputs. Arguing that every single user should be forced to restart an interactive si= gning session. That=A1=AFs a very strong statement based on something that I= would say is a preference that depends on circumstances. What about an optional commitment to witness size in bytes? The value zero m= eaning =A1=B0I don=A1=AFt care.=A1=B1 I would argue that it should be a maxi= mum however, and therefor serialized as part of the witness. The serializati= on of this would be very compact (1 plus the difference between actual and m= aximum, with zero meaning not used.)=