A person or group made off with $18 million in bitcoin gold after gaining control of 51 percent of the network's hash power.
On May 18, 2018, the bitcoin gold network suffered what could be a multi-million-dollar loss from a 51 percent attack. During the attack, the perpetrator was able to steal 388,201 BTG, presently worth approximately 18.2 million dollars.
In a public post[1], Ed Iskra from the bitcoin gold (BTG) network announced, "An unknown party[2] with access to very large amounts of hash power is trying to use '51 percent attacks' to perform 'double spend' attacks to steal money from Exchanges."
To complete a 51 percent attack, the attacker(s) must first gain control of at least 51 percent of the network's hash power in order to "control, exclude and modify the ordering of transactions."
Once the person, or group of people, obtains control over the network, they are not able to make transactions with other miners' coins because that would require them to have access to private keys. However, they can make transactions with their own coins, or exclude certain transactions from a block. According to Iskra's post, this ability allows them to:
- "Reverse transactions that they send while in control. This has the potential to double-spend transactions that previously had already been seen in the block chain.
- Prevent some or all transactions from gaining any confirmations
- Prevent some or all other miners from mining any valid blocks"
One lure of a 51 percent attack is the "double spending" aspect.
Attackers begin to mine on a chain forked from the original chain until theirs is longer, with more verifying nodes to support its claim of veracity. (In this most recent case, the entity or entities minted, on their competing fork, an additional
