Bitcoin Gold suffers 51% attack again

In a tweet released yesterday, the Bitcoin Gold team shared that Bitcoin Gold suffered two deep reorgs on Thursday January 23. The first reverted ~1900 BTG, the second ~5267 BTG. The losses amount to around $87,500 at current prices. According to the Bitcoin Gold team, the attack was executed using hash power rented through NiceHash.

Why it matters:

• This is Bitcoin Gold’s second 51% attack in its short existence. The first occurred in May 2018, where ~$18 million of the cryptocurrency was doubled spent.
• The attack highlights a significant flaw of optimizing a proof-of-work coin for ASIC-resistance. Such projects open their attack surface significantly given that GPUs and CPUs have use cases other than cryptocurrency mining. This makes it unknowable how much idle hash power is out there.