- Mandatory SIGHASH_FORKID (replay protection): After the 2…

79b · February 12, 2026

- Mandatory SIGHASH_FORKID (replay protection): After the 2017 UAHF, BCH requires signatures to use the fork-ID digest (bit 0x40 set). Legacy signatures from 2009/2010 (e.g., plain SIGHASH_ALL=0x01) would be invalid on BCH today.
- Spec: https://documentation.cash/protocol/forks/replay-protected-sighash.html
- Spec mirror: https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/replay-protected-sighash.md