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| (4人の利用者による、間の6版が非表示) |
| 1行目: |
1行目: |
| | + | このページではBIP（Bitcoin Improvement Proposal）について説明します。 |
| | + | BIPの詳細と作成方法については、[https://github.com/bitcoin/bips/blob/master/bip-0002.mediawiki BIP 2]を参照してください。<br> |
| | + | wikiページを作成するだけではありません。 |
| | <pre> | | <pre> |
| − | BIP: 113 | + | BIP：113 |
| − | Title: Median time-past as endpoint for lock-time calculations | + | タイトル：ロックタイム計算のエントリーポイントとしての時間中央値の中央値 |
| − | Author: Thomas Kerin <me@thomaskerin.io> | + | 著者：Thomas Kerin <me@thomaskerin.io> |
| − | Mark Friedenbach <mark@friedenbach.org> | + | Mark Friedenbach <mark@friedenbach.org> |
| − | Status: Draft | + | ステスタス：下書き |
| − | Type: Standards Track | + | タイプ：標準トラック |
| − | Created: 2015-08-10 | + | 作成日：2015-08-10 |
| | </pre> | | </pre> |
| | | | |
| − | | + | このBIPの全文は[[bip-0113.mediawiki]]で読むことができます。 |
| − | ==Abstract==
| |
| − | | |
| − | This BIP is a proposal to redefine the semantics used in determining a
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| − | time-locked transaction's eligibility for inclusion in a block. The
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| − | median of the last 11 blocks is used instead of the block's timestamp,
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| − | ensuring that it increases monotonically with each block.
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| − | | |
| − | | |
| − | ==Motivation==
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| − | | |
| − | At present, transactions are excluded from inclusion in a block if the
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| − | present time or block height is less than or equal to that specified
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| − | in the locktime. Since the consensus rules do not mandate strict
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| − | ordering of block timestamps, this has the unfortunate outcome of
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| − | creating a perverse incentive for miners to lie about the time of
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| − | their blocks in order to collect more fees by including transactions
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| − | that by wall clock determination have not yet matured.
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| − | | |
| − | This BIP proposes comparing the locktime against the median of the
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| − | past 11 block's timestamps, rather than the timestamp of the block
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| − | including the transaction. Existing consensus rules guarantee this
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| − | value to monotonically advance, thereby removing the capability for
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| − | miners to claim more transaction fees by lying about the timestamps of
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| − | their block.
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| − | | |
| − | This proposal seeks to ensure reliable behaviour in locktime calculations as
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| − | required by BIP65 (CHECKLOCKTIMEVERIFY), BIP68 (sequence numbers), and BIP112 (CHECKSEQUENCEVERIFY).
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| − | | |
| − | | |
| − | ==Specification==
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| − | | |
| − | The values for transaction locktime remain unchanged. The difference is only in
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| − | the calculation determining whether a transaction can be included. Instead of
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| − | an unreliable timestamp, the following function is used to determine the current
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| − | block time for the purpose of checking lock-time constraints:
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| − | | |
| − | enum { nMedianTimeSpan=11 };
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| − |
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| − | int64_t GetMedianTimePast(const CBlockIndex* pindex)
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| − | {
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| − | int64_t pmedian[nMedianTimeSpan];
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| − | int64_t* pbegin = &pmedian[nMedianTimeSpan];
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| − | int64_t* pend = &pmedian[nMedianTimeSpan];
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| − | for (int i = 0; i < nMedianTimeSpan && pindex; i++, pindex = pindex->pprev)
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| − | *(--pbegin) = pindex->GetBlockTime();
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| − | std::sort(pbegin, pend);
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| − | return pbegin[(pend - pbegin)/2];
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| − | }
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| − | | |
| − | Lock-time constraints are checked by the consensus method IsFinalTx(),
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| − | or LockTime() under BIP68. These methods take the block time as one
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| − | parameter. This BIP proposes that after activation calls to
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| − | IsFinalTx() or LockTime() within consensus code use the return value
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| − | of `GetMedianTimePast(pindexPrev)` instead.
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| − | | |
| − | A reference implementation of this proposal is provided by the
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| − | following pull request:
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| − | | |
| − | https://github.com/bitcoin/bitcoin/pull/6566
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| − | | |
| − | | |
| − | ==Deployment==
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| − | | |
| − | We reuse the double-threshold switchover mechanism from BIPs 34 and
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| − | 66, with the same thresholds, but for nVersion = 8. The new rules are
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| − | in effect for every block (at height H) with nVersion = 8 and at least
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| − | 750 out of 1000 blocks preceding it (with heights H-1000..H-1) also
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| − | have nVersion = 8. Furthermore, when 950 out of the 1000 blocks
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| − | preceding a block do have nVersion = 8, nVersion = 3 blocks become
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| − | invalid, and all further blocks enforce the new rules.
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| − | | |
| − | When assessing the block version as mask of ~0x20000007 must be applied
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| − | to work around the complications caused by
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| − | [http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-August/010396.html BIP101's premature use] | |
| − | of the [https://gist.github.com/sipa/bf69659f43e763540550 undecided version bits proposal].
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| − | | |
| − | By applying ~0x20000007 with nVersion = 8, the thresholds should be tested
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| − | comparing block nVersion >= 4 as this will save a bit for future use.
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| − | | |
| − | It is recommended that this soft-fork deployment trigger include other related
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| − | proposals for improving Bitcoin's lock-time capabilities, including:
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| − | | |
| − | [https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki BIP 65]:
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| − | CHECKLOCKTIMEVERIFY,
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| − | | |
| − | [https://github.com/bitcoin/bips/blob/master/bip-0068.mediawiki BIP 68]:
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| − | Consensus-enforced transaction replacement signalled via sequence numbers,
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| − | | |
| − | and [https://github.com/bitcoin/bips/blob/master/bip-0112.mediawiki BIP 112]:
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| − | CHECKSEQUENCEVERIFY.
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| − | | |
| − | | |
| − | ==Acknowledgements==
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| − | | |
| − | Mark Friedenbach for designing and authoring the reference
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| − | implementation of this BIP.
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| − | | |
| − | Thanks go to Gregory Maxwell who came up with the original idea,
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| − | in #bitcoin-wizards on 2013-07-16.
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| − | | |
| − | Thomas Kerin authored this BIP document.
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| − | | |
| − | | |
| − | ==Compatibility==
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| − | | |
| − | Transactions generated using time-based lock-time will take
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| − | approximately an hour longer to confirm than would be expected under
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| − | the old rules. This is not known to introduce any compatibility
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| − | concerns with existing protocols.
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| − | | |
| − | | |
| − | ==References==
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| − | [https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki BIP65: OP_CHECKLOCKTIMEVERIFY]
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| − | | |
| − | [https://github.com/bitcoin/bips/blob/master/bip-0068.mediawiki BIP68: Consensus-enforced transaction replacement signaled via sequence numbers]
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| − | | |
| − | [https://github.com/bitcoin/bips/blob/master/bip-0112.mediawiki BIP112: CHECKSEQUENCEVERIFY]
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| − | | |
| − | [http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-August/010396.html Softfork deployment considerations]
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| − | | |
| − | [https://gist.github.com/sipa/bf69659f43e763540550 Version bits]
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| − | | |
| − | | |
| − | ==Copyright==
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| − | | |
| − | This document is placed in the public domain.
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| − | | |
| − | [[Category:Developer]]
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| − | [[Category:Technical]]
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| − | [[Category:BIP|D]]
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