Skip to content

May 2018 Hardfork Specification

Version 1.1, 2018-04-09

Summary

When the median time past[1] of the most recent 11 blocks (MTP-11) is greater than or equal to UNIX timestamp 1526400000 Bitcoin Cash will execute a hardfork according to this specification. Starting from the next block these consensus rules changes will take effect:

  • Blocksize increase to 32,000,000 bytes
  • Re-enabling of several opcodes

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

  • Automatic replay protection for future hardforks
  • Increase OP_RETURN relay size to 223 total bytes

Blocksize increase

The blocksize hard capacity limit will be increased to 32MB (32000000 bytes).

OpCodes

Several opcodes will be re-enabled per may-2018-reenabled-opcodes

Automatic Replay Protection

When the median time past[1] of the most recent 11 blocks (MTP-11) is greater than or equal to UNIX timestamp 1542300000 (November 2018 hardfork) Bitcoin Cash full nodes implementing the May 2018 consensus rules SHOULD enforce the following change:

  • Update forkid[1] to be equal to 0xFF0001. ForkIDs beginning with 0xFF will be reserved for future protocol upgrades.

This particular consensus rule MUST NOT be implemented by Bitcoin Cash wallet software.

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

License of this document

The MIT License (MIT)

Copyright (c) 2017-2018 bitcoincash.org

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.