4 August 2021

The blockchain supporting Bitcoin SV has suffered a 51% attack, security experts say.

In a 51% attack, miners on a Proof of Work blockchain conspire to replace valid transactions with counterfeit data – essentially rewriting the past. If more than 50% of validating nodes accept the fraudulent transactions, the conspirators can siphon off cryptocurrency by erasing transactions and replacing them with new data. This creates a new version of the blockchain. And since the conspirators control more than 50% of the nodes, they are able to validate the fraudulent chain.

These attacks are theoretically possible on Proof of Stake networks too, but the hackers would have to own 51% of the target cryptocurrency.

Bitcoin SV was created in November 2018 as a fork of Bitcoin Cash. The fork was intended to cleave closely to Satoshi Nakamura’s original plan for Bitcoin – the “SV” stands for “Satoshi’s vision.”

According to a tweet from analysts at Blockchair, the attack erased 570,000 transactions from the BSV blockchain.

Bitcoin Association, which manages Bitcoin SV, has published instructions that tell miners how to mark the attacker-created versions of the blockchain as fraudulent, which should return BSV to business as usual.