May 2018 Hardfork Specification
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.