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62 lines
2.8 KiB
Text
62 lines
2.8 KiB
Text
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<pre>
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BIP: ?
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Layer: Consensus (soft fork)
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Title: Generic anti-replay protection using Script
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Author: Luke Dashjr <luke+bip@dashjr.org>
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Comments-Summary: No comments yet.
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Comments-URI: FIXME
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Status: Draft
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Type: Standards Track
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Created: 2017-01-26
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License: BSD-2-Clause
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</pre>
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==Abstract==
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This BIP describes a new opcode (OP_CHECKBLOCKATHEIGHT) for the Bitcoin scripting system that allows construction of transactions which are valid only on specific blockchains.
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==Copyright==
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This BIP is licensed under the BSD 2-clause license.
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==Specification==
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OP_CHECKBLOCKATHEIGHT redefines the existing NOP5 opcode.
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When executed, if any of the following conditions are true, the script interpreter will terminate with an error:
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* the stack has fewer than 2 elements; or
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* the top item on the stack is not interpretable as a minimal-length CScriptNum; or
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* the top item on the stack, when interpreted as a block height (see below) is not within the range of allowed blocks; or
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* the second-to-top item on the stack, when interpreted as a block hash, has leading zeros; or
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* the second-to-top item on the stack does not match the block hash of the block specified by the top item on the stack interpreted as a height.
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Otherwise, script execution will continue as if a NOP had been executed.
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FIXME: some way to mask out parts of the block hash for gambling/deterministic-random applications?
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===Block height interpretation and limits===
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The specified block height may be either a negative number to specify a relative height, or a positive number for an absolute height.
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A value of -1 refers to the block immediately preceding the block the transaction is mined it (but this is not a valid value, note).
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The specified height must not be more recent than the previous 100 blocks (that is, the largest negative value allowed is -101), nor older than 262144 blocks prior (ie, the smallest negative value is -262144).
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===Deployment===
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This BIP will be deployed by "version bits" BIP9 with the '''name''' TBD and using '''bit''' TBD.
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For Bitcoin '''mainnet''', the BIP9 '''starttime''' will be TBD (Epoch timestamp TBD) and BIP9 '''timeout''' will be TBD (Epoch timestamp TBD).
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For Bitcoin '''mainnet''', the BIP9 '''starttime''' will be TBD (Epoch timestamp TBD) and BIP9 '''timeout''' will be TBD (Epoch timestamp TBD).
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==Motivation==
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In the event of a permanent blockchain split, some mechanism is desired by which the UTXOs valid in either chain may be spent without the transaction being validly replayable on the other chain.
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Additionally, there are some cases in normal Bitcoin operation wherein a wallet may need to respend a payment, but must guarantee its respend cannot be mined in the same block as a previous payment which has been recently conflicted by a double-spend.
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==Reference Implementation==
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TODO
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