What is double-spending in the bitcoin network?

18th April 2021

Bitcoin is a very secure platform, and you also have some advantages and disadvantages of everything. If bitcoin provides security, then there are some attackers or hackers that find multiple ways to attack or crack, and in this platform, the common and easy attack is double-spending. Bitcoin platform requires six confirmations to complete a transaction and if it roughly in 10 minutes and can take up to one hour. So you have to wait for six confirmations before sending money to another person or anyone. This article will discuss the double-spending and attacks that happen in the bitcoin network or blockchain as per bitqs.io .

What is double-spending in blockchain?

For the valid transaction, six confirmation is required, and it is shown as n/unconfirmed, and n indicates the number of assurances done for a single transaction. Double spending means spending your bitcoin twice. Suppose you are sending a bitcoin to your friend, and then after sending it, that is 0/unconfirmed, and you have to send another bitcoin to your other friend, and it will happen as double-spending. It means that you have no bitcoin left, and you are trying to send the same bitcoin to another bitcoin user.

Why double-spending happens

The reason for double-spending is that people don’t wait for the six confirmations, and it will happen as double-spending. Merchants and traders or buyer and seller don’t wait for six confirmation. The seller instantly transfers the bitcoin to another user’s account and thinks I have sent bitcoin though it is unconfirmed.

When you send bitcoin to the wallet of someone, then your transaction stored in the blockchain and the confirmation process is started, and it can take up to an hour. After sending the bitcoin that is not confirmed, people instantly try to send bitcoins to another person thinking that bitcoin is available in my account.

Five forms of attacks in double spending

There are following five types of double-spending attacks given below:-

  1. Race Attack

Race attack happens when people accept instant payment into their wallet without the six confirmations. They spend the amount instantly after checking the 0/unconfirmed, which means the transaction is not valid. When the one transaction has successfully happened, and the user will communicate another trade with the same amount, it will be fraudulent and known as a race attack.

  1. Finney attack

It is also a result of double-spending. In this attack, the attack is familiar with the mining process, or we can say the person is a minor and know about the mining process. The attack can happen with the involvement of a minor. The little send bitcoin to his wallet, and he has not broadcasted the transaction since the transaction is not disclosed on the blockchain. Unconfirmed, he purchased goods or services from the merchant and then transferred that amount to the merchant and merchant’s wallet. Still, on the blockchain, the merchant thinks, I have received the bitcoin, but on the blockchain, a sender transmits the bitcoin amount into his wallet.

  1. Vector 76 attack

This attack is the combination of race attack and Finney attack. The merchant accepts payment without waiting for the confirmations, and they delivered goods or services to the sender. In the race attack, they will receive compensation instantly and do not wait for the validation, and in the Finney attack, minors are involved or required. They spend bitcoin in their wallet since their transaction is not confirmed; after that, they transfer the same amount to the merchant’s wallet, and after an hour, the merchant cannot complain to anyone. To prevent this attack, wait for the six confirmations or more before going to step further.

  1. >50% attack

This attack is used by a single miner or group of minors. As we know that minors have proper knowledge of mathematical equations, and they can solve complex mathematical equations. More than 50% of the bitcoin network is controlled by these minors, whether single or group of minors. The chances of attacks are 100 per cent because they can create a block for bitcoin transaction very fast than the rest of the blockchain working.


From the above information, double spending means spending your bitcoin twice. Each transaction is a valid transaction, the six confirmation of a block of commerce, and if you want to prevent these attacks, then wait for six or more confirmations.