[bitcoin-dev] BIP: OP_BRIBVERIFY - the op code needed for Blind Merge Mined drivechains

<pre> BIP: <BIP number> Layer: Consensus (Soft fork) Title: OP_BRIBEVERIFY Author: Chris Stewart <chris at suredbits.com> Status: Draft Type: Standards Track Created: 2017-06-27 </pre> ==Abstract== This BIP describes a new opcode, OP_BRIBEVERIFY, for the Bitcoin scripting system that allows for a user to bribe a miner to include a hash in the coinbase transaction's output. ==Summary== BRIBEVERIFY redefines the existing NOP4 opcode. When executed, if the given critical hash is included at the given vout index in the coinbase transaction the script evaluates to true. Otherwise, the script will fail. This allows sidechains to be merged mined against bitcoin without burdening bitcoin miners with extra resource requirements. ==Motivation== The current political climate of bitcoin is extremely contentious. Many community members have different visions of what bitcoin is. This op code is meant to enable [http://www.truthcoin.info/blog/blind-merged-mining/ Blind Merge Mining]. This enables sidechains in Bitcoin. With OP_BRIBEVERIFY, sidechains miners can bribe bitcoin miners to to include their block hash in the bitcoin blockchain. If their block is included in the coinbase transaction's vout, it is assumed that block is a mined block on the sidechain. This will allow various factions of the community to realize their vision on their own separate blockchain that is interoperable with the bitcoin blockchain. This allows those factions to use bitcoin as a 'reserve currency' for their own network. ===Commitment Structure=== A new block rule is added which requires that the miner's coinbase reward be at index 0 in the coinbase transaction's output vector. It also fixes the witness commitment output to be at index 1 of the coinbase transaction's output vector. This is needed so we can reliably tell what vout corresponds to what drivechain. For instance, the mimblewimble sidechain could correspond to index 2 of the vector outputs on the coinbase transaction. The commitment is recorded in a <code>scriptPubKey</code> of the coinbase transaction. It must be at least 34 bytes in size 1-byte - OP_RETURN (0x6a) 1-byte - Push the following 32 bytes (0x20) 32-byte - block hash the 35th byte and onward have no consensus meaning. ===OP_BRIBEVERIFY op code=== This op code reads two arguments from the stack. The stack top is expected to be a sidechain id for which this user attempting to blind merge mine for. The next element on the stack is expected to be a block hash. This op code looks into the coinbase transaction's output vector at the given index (which is derived from the sidechain id) and checks to see if the hash in the block matches the hash inside of the BRIBEVERIFY program. If the hashes match, the OP_BRIBEVERIFY acts as an OP_NOP. If the comparison between the two hashes fail, the script fails. ===BRIBEVERIFY program=== A standard BRIBEVERIFY program has the format: 1-byte - Push the following 32 bytes (0x20) 32-byte - block hash 1 byte - Push operation? (needed if number can't be encoded as OP_0 - OP_16) 1 byte - sidechain id 1 byte - OP_BRIBEVERIFY op code ==Detailed Specification== Refer to the reference implementation, reproduced below, for the precise semantics and detailed rationale for those semantics. case OP_NOP4: { //format: block_hash sidechain_id OP_BRIBEVERIFY if (!(flags & SCRIPT_VERIFY_BRIBEVERIFY)) { // not enabled; treat as a NOP4 if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS) { return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS); } break; } if (stack.size() < 2) return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION); const CScriptNum scriptNumSidechainId(stacktop(-1),fRequireMinimal); uint8_t nSidechainId; if (!checker.CheckSidechainId(scriptNumSidechainId,nSidechainId)) { return set_error(serror, SCRIPT_ERR_UNKNOWN_SIDECHAIN); } // Check block hash bool fHashCritical = checker.CheckCriticalHash(stacktop(-2),nSidechainId); if (!fHashCritical) { return set_error(serror, SCRIPT_ERR_UNSATISFIED_BRIBE); } break; } https://github.com/Christewart/bitcoin/blob/94b6f33f2278c42d4d8758a3c8ffe2078e4ec933/src/script/interpreter.cpp#L427 https://github.com/drivechain-project/bitcoin/pull/13 ==Deployment== TODO ==Credits== Credit to Paul Sztorc for the original idea of Blind Merge Mined sidechains. Credit to CryptAxe for writing the foundational layer of software for drivechains so I could implement OP_BRIBEVERIFY. ==References== Blind Merge Mined Sidechains - http://www.truthcoin.info/blog/blind-merged-mining/ Mailing list discussion - https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-May/014408.html ==Copyright== This document is placed in the public domain. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/attachments/20170627/bd5730bf/attachment.html>