One Day After the Bitcoin Cash Hard Fork: Takeaways and Latest Developments

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).

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 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, 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 “Bitcoin Cash ABC Classic.” (These names are just hypothetical, made up for the purpose of this article.)

That said, such a split seems unlikely at the moment. According to forkmonitor.info, it would cost around $1 million to pull off at the time of writing this article.

Future Attacks

While Bitcoin Cash ABC proponents generally seem confident of their “victory,” many Bitcoin Cash SV proponents are not conceding defeat.

For example, nChain chief scientist and the main man behind Bitcoin SV, Craig Steven Wright, tweeted that the “hash war” is a marathon, not a sprint: implying attacks are still coming. Coingeek and its owner, Calvin Ayre, similarly claim the hash war has only just started. Other Bitcoin Cash SV proponents also anticipate other types of attacks (like a type of spam attack dubbed “Satoshi’s Shotgun”). All this will eventually obliterate the Bitcoin Cash ABC chain, they say.

There is no evidence of these types of attacks coming, perhaps with the exception of Satoshi’s Shotgun. The Bitcoin Cash network did experience a big spam-type of attack last week, and there was also much spam on the Bitcoin Cash network around the time of the hard fork. This may have been a precursor.

It is also true that the status of the Bitcoin Cash ABC network was unusual for the past day, as an excessive amount of hash power was securing it (excessive relative to its respective profitability, which suggests miners were mining at a loss). This was in part because the bitcoin.com pool temporarily diverted its hash power from mining Bitcoin to mining Bitcoin Cash ABC.

Over time, it is to be expected that the amount of hash power securing the Bitcoin Cash ABC chain will decrease to normal levels (normal relative to the expected profitability). The Bitcoin Cash ABC network would then also be more susceptible to 51-percent attacks.

Name and Tickers

With Bitcoin Cash split into two different coins, there is some contention about the names of both.

What is clear, however, is that the two main software implementations are called “Bitcoin ABC” and “Bitcoin SV.”

So far, Bitcoin Magazine has for the purpose of this article referred to the protocol and blockchain based on the Bitcoin ABC implementation as “Bitcoin Cash ABC,” while the protocol and blockchain based on Bitcoin SV has been called “Bitcoin Cash SV.” The respective currency tickers used have been “BCH ABC” and “BCH SV.” But not everyone uses these names and tickers.

Many Bitcoin Cash ABC supporters in particular instead consider their protocol and blockchain to be “Bitcoin Cash,” and some probably even prefer “Bitcoin.” They also claim the ticker “BCH.”

Many Bitcoin Cash SV proponents feel it’s too soon to rename anything, as they still think there will be only one chain left standing in the end: Bitcoin Cash SV, to be named “Bitcoin Cash” (or “Bitcoin”) with the ticker “BCH.”

Others have come up with different names and (especially) ticker symbols altogether. These most notably include “BAB” for BCH ABC and “BSV” for BCH SV. And some exchanges don’t list BCH SV at all.

For a more complete overview of the different names and tickers, see this article.

For more information about yesterday’s hard fork, see this article.

Thanks to Sjors Provoost for feedback and additional sources.