51% Attack

51% Attack

A 51% attack refers to a scenario in Blockchain networks, particularly those using Proof of Work (PoW), where a single entity or group of entities gains control of more than 50% of the network’s mining hash rate. This majority control allows the attacker to manipulate the Blockchain by double-spending coins, blocking transactions, or preventing other miners from successfully mining new blocks.

Examples:

• Bitcoin Gold (2018): Bitcoin Gold experienced a 51% attack where the attacker was able to double-spend approximately $18 million worth of BTG.
• Ethereum Classic (2019): Ethereum Classic suffered multiple 51% attacks, resulting in double-spending incidents that led to the loss of around $1.1 million.

Cases:

• Vertcoin (2018): Vertcoin experienced a 51% attack that allowed the attacker to reverse transactions and double-spend coins.
• SecureCoin (2014): A 51% attack on SecureCoin led to the loss of funds, as the attacker was able to rewrite transaction history.