Bitcoin Cash, the “big block” project that forked away from the Bitcoin blockchain in August 2017, “hard forked” (split) into two different coins: “Bitcoin Cash ABC” (BCH ABC) and “Bitcoin Cash SV” (BCH SV).
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At the time of writing, the Bitcoin Cash ABC chain has more accumulated proof of work, and its native currency, BCH ABC, is trading higher on (futures) exchanges. Most Bitcoin Cash ABC proponents, therefore, feel victorious — though many Bitcoin Cash SV proponents have not yet conceded defeat.
Well over a day since the split, here are the main takeaways and latest developments.
Checkpoint Controversy
It turns out that the Bitcoin ABC development team had a trick up its sleeve — and not everyone is happy with that. The developers included an unannounced checkpoint in their latest software release, which was distributed[2] several hours after the fork.
The checkpoint enforces inclusion of the first Bitcoin Cash ABC block as a new protocol rule. Any chain without this block would be considered invalid by this Bitcoin ABC software client. This has the effect that adversarial miners are unable to override (“re-org”) the entire Bitcoin Cash ABC chain — which was one of the potential threats posed by a “hash war.”
The checkpoint is controversial[3], however, as it implies central control from the Bitcoin ABC development team over the Bitcoin Cash ABC chain. Where nodes usually follow the longest valid proof-of-work chain, a checkpoint is perceived to override this proof-of-work consensus mechanism.
Of course, users ultimately decide which software they run and can opt to reject the checkpointed version of Bitcoin ABC. But this opens up the risk of the checkpoint causing another split — this time, on the Bitcoin Cash ABC chain, creating “Bitcoin Cash ABC Checkpoint” and
