From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1YmKqc-0000XG-9j for bitcoin-development@lists.sourceforge.net; Sun, 26 Apr 2015 11:35:42 +0000 Received: from mail-wi0-f177.google.com ([209.85.212.177]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1YmKqZ-0005HR-UU for bitcoin-development@lists.sourceforge.net; Sun, 26 Apr 2015 11:35:42 +0000 Received: by wicmx19 with SMTP id mx19so64298920wic.1 for ; Sun, 26 Apr 2015 04:35:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=VsvLhQXYTuuvfJ4kA0hwry7nU2B+jPALJoHwB/fSMvE=; b=artD8JYAtYAMmhvbRSdLYMTQ6txFLmeYqddq/YTXlhkjZYmtKD5YeuvY4ZYkTxWKbi dkime2vQdRNs5XUz6ZsHL+wC++Y6mAl/LNvjDFuok68cfx2Y1lKmaqciBygexcDt3jcx Bv9izdbu+n7NNXzCmhQUwVUYmHeSqexMAokpjawMkv+hnEYVhdBQjWlpnFtGxRxvWJjR m96yjjzAAI9pHTrGKSgWGlpVlPzeWwFesW6IyJlXtssDbTk0nf3WanvX7652QqASR205 KNRaiDZpBTu5bslFTI1uPXou30gT54xMa/I8+0d1UTWtfS3OYiQbrk94jviNPcnvNtVF agfw== X-Gm-Message-State: ALoCoQnehoGBvROEd1Mwy896U31Nt7YQ/Jx3+9lH6ULiL7j1kRloetmdKIhYuvk2pT9tmEh73cS7 MIME-Version: 1.0 X-Received: by 10.180.37.73 with SMTP id w9mr12031409wij.7.1430048133662; Sun, 26 Apr 2015 04:35:33 -0700 (PDT) Received: by 10.194.124.2 with HTTP; Sun, 26 Apr 2015 04:35:33 -0700 (PDT) In-Reply-To: <20150421075912.GA25282@savin.petertodd.org> References: <20141001130826.GM28710@savin.petertodd.org> <55075795.20904@bluematt.me> <20150421075912.GA25282@savin.petertodd.org> Date: Sun, 26 Apr 2015 13:35:33 +0200 Message-ID: From: =?UTF-8?B?Sm9yZ2UgVGltw7Nu?= To: Peter Todd Content-Type: text/plain; charset=UTF-8 X-Spam-Score: 0.0 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. X-Headers-End: 1YmKqZ-0005HR-UU Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] Relative CHECKLOCKTIMEVERIFY (was CLTV proposal) X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 26 Apr 2015 11:35:42 -0000 On Tue, Apr 21, 2015 at 9:59 AM, Peter Todd wrote: > Thus we have a few possibilities: > > 1) RCLTV against nLockTime > > Needs a minimum age > COINBASE_MATURITY to be safe. > > > 2) RCLTV against current block height/time > > Completely reorg safe. Yes, can we call this one OP_MATURITY to distinguish it from RCLTV? > 3) GET_TXOUT_HEIGHT/TIME ADD CLTV > > To be reorg safe GET_TXOUT_HEIGHT/TIME must fail if minimum age < > COINBASE_MATURITY. This can be implemented by comparing against > nLockTime. Mhmm, interesting. > All three possibilities require us to make information about the > prevout's height/time available to VerifyScript(). The only question is > if we want VerifyScript() to also take the current block height/time - I > see no reason why it can't. As for the mempool, keeping track of what > transactions made use of these opcodes so they can be reevaluated if > their prevouts are re-organised seems fine to me. I'm totally fine with changing the interface to: int bitcoinconsensus_verify_script(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, const unsigned char *txTo , unsigned int txToLen, unsigned nHeight, unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err); I prefer op_maturity over RCLTV and there are also gains for absolute CLTV as you explain later. When you validate the script inputs of a transaction you already have a height, either the real final nHeight in ConnectBlock and the miner, or nSpendHeight in AcceptToMemoryPool. The costs are meaningless in my opinion, specially when we will already have to change the interface to add libsecp256k1's context. I'm infinitely more worried about the other assumption that the 3 solutions are already making. Changing to int bitcoinconsensus_verify_script(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, const unsigned char *txTo , unsigned int txToLen, const CCoinsViewCache& inputs, unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err); Is simply not possible because CCoinsViewCache is a C++. You could solve it in a similar way in which you could solve that dependency for VerifyTransaction. For example: typedef const CTxOut& (*TxOutputGetter)(const uint256& txid, uint32_t n); int bitcoinconsensus_verify_script(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, const unsigned char *txTo , unsigned int txToLen, TxOutputGetter utxoGetter, unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err); Of course, this is assuming that CTxOut becomes a C struct instead of a C++ class and little things like that. In terms of code encapsulation, this is still 100 times uglier than adding the nHeight so if we're doing it, yes, please, let's do both. There's another possibility that could keep the utxo out of Script verification: class CTxIn { public: COutPoint prevout; CScript scriptSig; uint32_t nSequence; } could turn into: class CTxIn { public: COutPoint prevout; CScript scriptSig; uint32_t nHeight; } And a new softfork rule could enforce that all new CTxIn set nHeight to the correct height in which its corresponding prevout got into the chain. That would remove the need for the TxOutputGetter param in bitcoinconsensus_verify_script, but unfortunately it is not reorg safe (apart from other ugly implementation details). So, in summary, I think the new interface has to be something along these lines: int bitcoinconsensus_verify_script(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, const unsigned char *txTo, unsigned int nIn, unsigned int txToLen, TxOutputGetter utxoGetter, unsigned nHeight, secp256k1_context_t *ctx unsigned int flags, bitcoinconsensus_error* err); > Time-based locks > ================ > > Do we want to support them at all? May cause incentive issues with > mining, see #bitcoin-wizards discussion, Jul 17th 2013: > > https://download.wpsoftware.net/bitcoin/wizards/2013/07/13-07-17.log I'm totally fine not supporting time-based locks for the new operators. Removing them from the regular nLockTime could be more complicated but I wouldn't mind either. Every time I think of a contract or protocol that involves time, I do it in terms of block heights. I would prefer to change all my clocks to work in blocks instead of minutes over changing nHeights for timestamps in any of those contracts. > -- > 'peter'[:-1]@petertodd.org > 0000000000000000015e09479548c5b63b99a62d31b019e6479f195bf0cbd935 > > ------------------------------------------------------------------------------ > BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT > Develop your own process in accordance with the BPMN 2 standard > Learn Process modeling best practices with Bonita BPM through live exercises > http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ > source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_SF > _______________________________________________ > Bitcoin-development mailing list > Bitcoin-development@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bitcoin-development >