According to a post on Github, the Bitcoin Gold (BTG) platform has been hit attacked. The post says that the blockchain was hit with a 51% attack on two different days. The network lost more than $70,000 worth of BTG.
MIT Digital Currency Initiative researcher James Lovejoy made a post, claiming that the network suffered two deep reorganizations, causing double-spending.
The first occurrence reportedly happened at exactly 18:01:32 GMT, on Thursday, 23 January 2020. In that occurrence, 14 blocks were removed from the network, with 13 added. Lovejoy says that 1,900 BTG, roughly $19,00, was double spent.
Hours later, at exactly 00:24:08 on Friday, 24 January 2020, another 15 blocks were removed with 16 blocks added. In this second occurrence, a total of 5,267 BTG, roughly $53,000 was double-spent. The second occurrence took three transactions of 1,947 BTG, 1,850 BTG, and 1,470 BTG.
Zhash is the algorithm that powers the Bitcoin Gold network. According to Lovejoy, each reorganization is estimated to have cost about $1,700. The researcher also says that the attacker “would have recouped around the same value in block rewards.” He adds that:
“Therefore, it is possible that the attacks were profitable if the double-spends succeeded at defrauding the attacker’s counterparty, or break-even if the double-spends were unsuccessful”
In May 2019, the Bitcoin Cash (BCH) blockchain was also with a 51% attack.