HF-20200515

layout: specification
title: 2020-MAY-15 Network Upgrade Specification
date: 2020-04-26
category: spec
activation: 1589544000
version: 0.4

Summary

When the median time past [1] of the most recent 11 blocks (MTP-11) is greater than or equal to UNIX timestamp 1589544000 (May 15th, 2020, 12:00PM UTC), Bitcoin Cash will execute an upgrade of the network consensus rules according to this specification. Starting from the next block these consensus rules changes will take effect:

The following are not consensus changes, but are recommended policy changes for Bitcoin Cash implementations:

SigChecks

Enforcement of sigops limits is removed, and replaced with new limits based on the number of signature checks that are actually executed when running a script. This new system is called SigChecks.

Details can be found in the full specification: SigChecks.

OP_REVERSEBYTES

This new opcode reverses the order of bytes in a string. It can be used to change endianness.

Details can be found in the full specification: OP_REVERSEBYTES.

Infrastructure Funding Plan

The purpose of the Infrastructure Funding Plan (IFP) is to provide funding to development projects working on common Bitcoin Cash infrastructure. If activated, it enforces that 5% of the block reward is spent to one of a set of specified addresses. Activation is triggered via BIP 9 version bits signalling prior to the May 15 upgrade.

More detailed can be found in the full specification.

Automatic Replay Protection

The purpose of Automatic Replay Protection is to serve as a full node version-deprecation mechanism. It is intended to cause full validating nodes which do not upgrade, to automatically separate themselves from the main network after the next upgrade on 15 May 2020. Nodes which implement the next upgrade will remove this automatic replay protection, and thus all regular wallets can continue using the default ForkID with no change to follow the main upgraded chain.

When the median time past [1] of the most recent 11 blocks (MTP-11) is less than UNIX timestamp 1605441600 (Nov 2020 upgrade) Bitcoin Cash full nodes MUST enforce the following rule:

When the median time past [1] of the most recent 11 blocks (MTP-11) is greater than or equal to UNIX timestamp 1605441600 (Nov 2020 upgrade) Bitcoin Cash full nodes implementing the May 2020 consensus rules SHOULD enforce the following change:

This particular consensus rule MUST NOT be implemented by Bitcoin Cash wallet software. Wallets that follow the upgrade should not have to change anything.

References

[1] Median Time Past is described here. It is guaranteed by consensus rules to be monotonically increasing.

[2] The forkId is defined as per the replay protected sighash specification.