Final update 17:53 UTC: The Bitcoin Cash blockchain appears to be processing transactions normally. Most blocks found since the last update and include a few hundred transactions in them, with most having been processed by BTC.Top. It's believed the network is now reasonably safe once again.
Update 17:06 UTC: Two block with over 2,500 transactions combined has been mined. The BCH blockchain currently has blocks that could grow to as mcuh as 32 MB if needed, meaning the blockchain can easily clear the mempool it build up during the glitch. Available data shows the size of BCH's mempool dropped sharply after the block was mined.
Update 16:46 UTC: The BCH blockchain has seemingly started processing transactions once again. BTC.Top has recently mined a block that included 89 transactions, and an unknwon miner quickly managed to mine another block that included over 130 transations. This could mean BCH's developers applied a patch that fixed the issue.
Bitcoin Cash Blockchain Temporarily Struggled
After going through a planned update this Wednesday, May 15, 2019, the Bitcoin Cash network stopped processing transactions for various blocks, over what some were claiming to be an issue with the Bitcoin ABC client. The cryptocurrency's blockchain has since started processing transactions again.
According to Coin.Dance data, most blocks on the Bitcoin Cash blockchain mined after the hard fork were only processing the coinbase transaction, meaning unconfirmed transitions were piling up on the network and users weren't able to transact.
Behind the problem, according to a Reddit thread, was an “issue” with Bitcoin ABC, a client most cryptocurrency miners are running, that was stopping transactions from being processed. The issue, first spotted by BitMEX Research, could be unrelated to the scheduled hard fork.
It appears as if there may be a problem with the Bitcoin Cash hardfork upgrade, the number of txs per block is low (0 in the last 9 blocks, other than the coinbase txn). Our mempool has 1622 txs— BitMEX Research (@BitMEXResearch) May 15, 2019
Below chart is number of txs per block and the orange line is the hardfork point pic.twitter.com/UR3jQuN6Zm
On social media, some users have argued miners were processing empty blocks to avoid processing transactions that could be malicious, or that could be rolled back while the network was facing technical difficulties.
BCH’s mempool , since the hard fork upgrade, started adding large transactions (in terms of data) to it, which could suggest someone was indeed trying to take advantage of the situation. Bitcoin Cash’s core developers reportedly worked on fixing the problem as soon as possible.
According to BitMEX Research, Bitcoin Cash split into two blockchains, meaning a new cryptocurrency has been created. A hard fork is known as an upgrade that isn't backwards compatible, which means those who don't upgrade their software end up forking off of the main chain.
The Bitcoin Cash chain has split into two chains. A hardfork occurred at block 582,679, however since that block, upgraded and non-upgraded nodes have split onto different chains.— BitMEX Research (@BitMEXResearch) May 15, 2019
The Bitcoin Cash network may not currently be safe for payments https://t.co/U9hbK4peip pic.twitter.com/Yfcnp6G0Dj
According to Cornell University Professor Emin Gün Sirer, the BCH network wasn't processing transactions as it came “under attack,” thanks to an “old bug in block template creation.” Gün Sirer added that someone spent “months sitting on this bug,” but only chose to exploit it now, during the network upgrade.
BCH came under attack today, due to an old bug in block template creation. Attack led to empty blocks for a short while, until patched, otherwise had little effect.— Emin Gün Sirer (@el33th4xor) May 15, 2019
Meanwhile, cryptocurrency exchanges started to react to the problem, with Poloniex revealing it has disabled deposits and withdrawals in the cryptocurrency in the meantime.
BCH had an issue with the planned hard fork scheduled for today. As a result, we have disabled deposits and withdrawals for BCHABC until further notice. BCH core developers are working on it. Thank you for your patience.— Poloniex Exchange (@Poloniex) May 15, 2019
The cryptocurrency, which was created through a hard fork of the Bitcoin network in August of 2017, recently made headlines as it was outshining the wider crypto market rally this week. The hard fork, which added Schnorr Signatures to optimize the blockchain and added SegWit recovery, is believed to have helped its performance.
It’s worth noting that on November 15, 2018 the BCH network underwent a hard fork that led to the creation of Bitcoin Satoshi’s Vision (BSV).