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Andrew Groot
56 lines
2.7 KiB
Markdown
56 lines
2.7 KiB
Markdown
# HF-20201115
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layout: specification
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title: 2020-NOV-15 Network Upgrade Specification
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date: 2020-08-15
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category: spec
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activation: 1605441600
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version: 0.1
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## Summary
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When the median time past [[1]](#references) of the most recent 11 blocks (MTP-11) is greater than or equal to UNIX timestamp 1605441600 (Nov 15th, 2020, 12:00PM UTC),
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Bitcoin Cash will execute an upgrade of the network consensus rules according to this specification.
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Starting from the next block these consensus rules changes will take effect:
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* Bitcoin Cash's Difficulty Adjustment Algorithm (DAA) is replaced with a new system, referred to as aserti3-2d.
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The following are not consensus changes, but are recommended policy changes for Bitcoin Cash implementations:
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* Automatic replay protection for future upgrade.
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## Difficulty Adjustment Algorithm
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Bitcoin Cash's Difficulty Adjustment Algorithm (DAA) is replaced with a new algorithm called [ASERT](http://toom.im/files/da-asert.pdf).
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The specific implementation is called aserti3-2d. Details can be found in the [full specification: ASERT](/protocol/forks/2020-11-15-asert).
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## Automatic Replay Protection
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The purpose of Automatic Replay Protection is to serve as a full node version-deprecation mechanism. It is intended to cause
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full validating nodes which do not upgrade, to automatically separate themselves from the main network after the next
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upgrade on 15 May 2021. Nodes which implement the next upgrade will remove this automatic replay protection, and thus all regular
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wallets can continue using the default ForkID with no change to follow the main upgraded chain.
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When the median time past [[1]](#references) of the most recent 11 blocks (MTP-11) is less than UNIX timestamp 1621080000 (May 2021 upgrade)
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Bitcoin Cash full nodes MUST enforce the following rule:
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* `forkid` [[2]](#references) to be equal to 0.
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When the median time past [[1]](#references) of the most recent 11 blocks (MTP-11) is greater than or equal to UNIX timestamp 1621080000
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(May 2021 upgrade) Bitcoin Cash full nodes implementing the Nov 2020 consensus rules SHOULD enforce the following change:
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* Update `forkid` [[2]](#references) to be equal to `0xFFXXXX`, where `XXXX` is some arbitrary hex value.
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ForkIDs beginning with 0xFF will be reserved for future protocol upgrades.
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This particular consensus rule MUST NOT be implemented by Bitcoin Cash wallet software. Wallets that follow the upgrade
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should not have to change anything.
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## References
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[1] Median Time Past is described [here](/protocol/blockchain/transaction#median-time-past).
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It is guaranteed by consensus rules to be monotonically increasing.
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[2] The `forkId` is defined as per the [replay protected sighash](/protocol/forks/replay-protected-sighash) specification.
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