What is a Race Attack?
A race attack is an attack where an attacker sends the same coin to multiple vendors in rapid succession. The attacker hopes that one vendor will accept the transaction before it is rejected by the network. This type of attack is more likely to be successful if the vendor does not wait for block confirmation before delivering the goods.
How to Prevent a Race Attack
The most effective way to prevent a race attack is to wait for at least one block confirmation before sending out the goods. This ensures that the transaction will be accepted by the network before any goods are delivered.
Finney Attack
What is a Finney Attack?
A Finney attack is an attack where an attacker mines a block with his transaction and does not release it in the system. He then uses the same coins in a second transaction and releases the pre-mined block. The goal of this attack is to take advantage of the time it takes for other miners to reject the second transaction.
How to Prevent a Finney Attack
To prevent a Finney attack, the seller should wait for at least six block confirmations before releasing the goods. This ensures that the transaction is accepted by the majority of the network before any goods are delivered.
51% Attack
What is a 51% Attack?
A 51% attack is an attack where an attacker owns 51% of the computing power of the network. The attacker then mines a private blockchain where he double-spends the coins. As he owns the majority of computing power, he is guaranteed that his private blockchain will eventually be longer than the chain of the “honest” network.
How to Prevent a 51% Attack
This kind of attack is practically impossible to prevent as it is very expensive to acquire computing power which equals or exceeds 51% of the computing power of the entire network. This is why it is important to use a secure and trusted network to ensure that all transactions are valid.