A pinning attack is a type of attack in which an adversary replaces a previously sent transaction with a new one that has a significantly higher transaction fee. This can be used by an adversary to increase the time it takes for a transaction to be confirmed, or to prevent it from being confirmed at all. In this article, we discuss how an adversary can increase the fee required to replace a transaction by up to 500 times.
Understanding Transaction Fee Calculations
Before we get into the details of how an adversary can increase transaction fees, it’s important to understand how transaction fees are calculated. Transaction fees are calculated based on the size of the transaction in bytes and the applicable fee rate in satoshis per byte. The fee rate is determined by market demand for block space and may vary depending on network congestion.
Transaction size
The size of a transaction is determined by the number of inputs and outputs it has, as well as the size of the scripts used to redeem those inputs. The size of an input and output depends on the number of bytes required to represent it on the blockchain. The size of scripts depends on, among other things, the complexity of the script used.
Fee rate
The fee rate is determined by the market demand for block space. If there are many transactions waiting to be confirmed, the fee rate will increase as users compete to get their transactions confirmed quickly. Conversely, if there are few transactions waiting to be confirmed, the fee rate will decrease as users do not need to compete for block space.
Increase required transaction fees
An adversary can increase the required transaction fee by creating a new transaction with the same inputs as the original transaction, but with a higher fee rate. This new transaction will have a higher fee and will be more attractive to miners, who will prioritize it over the original transaction. The original transaction is then dropped from the mempool and is not confirmed.
Create replacement transaction
To create the replacement transaction, the adversary must first identify the transaction they wish to replace. They must then create a new transaction with the same inputs as the original transaction, but with a higher fee rate. The adversary can use any bitcoin wallet software to create the new transaction.
Sending the replacement transaction
Once the substitute transaction is created, the adversary must broadcast it to the bitcoin network. This can be done using any bitcoin wallet software. When the replacement transaction is broadcast, it is added to the mempool and begins competing with the original transaction for confirmation.
Preventing pinning attacks
There are a number of ways to prevent pinning attacks. One way is to use a wallet that has built-in protection against pinning attacks. Another way is to use a bitcoin transaction acceleration service, which can help increase the chances of a transaction being confirmed quickly.
Using a wallet with built-in protection
Some bitcoin wallets have built-in protection against pinning attacks. These wallets use a technique called transaction replacement detection, which detects when a new transaction attempts to replace an unconfirmed transaction with a higher fee rate. When such a transaction is detected, the wallet alerts the user and prevents the replacement transaction from being sent.
Use of a bitcoin transaction accelerator service
A bitcoin transaction accelerator service can help increase the chances of a transaction being confirmed quickly. These services work by submitting the transaction to a pool of miners who have agreed to prioritize transactions submitted to the accelerator service. There is a fee for this service, but it may be worth it if the transaction is urgent.
Closure
In conclusion, pinning attacks can be used by adversaries to increase the fee required to replace a transaction by up to 500 times. The best way to prevent these attacks is to use a Bitcoin wallet with built-in protection against pinning attacks or to use a Bitcoin transaction accelerator service. By taking these steps, users can ensure that their transactions are confirmed quickly and securely.
FAQs
Frequently Asked Questions
What is a pinning attack?
A pinning attack is a type of attack where an adversary replaces a previously broadcasted transaction with a new one, which has a significantly higher transaction fee.
How does transaction fee calculation work?
Transaction fees are calculated based on the size of the transaction in bytes and the prevailing fee rate in satoshis per byte.
How can an adversary increase required transaction fees?
An adversary can increase the required transaction fee by creating a new transaction with the same inputs as the original transaction but with a higher fee rate.
What happens to the original transaction when a replacement transaction is broadcast?
The original transaction will then be dropped from the mempool and will not be confirmed.
What are some ways to prevent pinning attacks?
One way is to use a wallet that has built-in protection against pinning attacks. Another way is to use a Bitcoin transaction accelerator service, which can help increase the chances of a transaction being confirmed quickly.
What is transaction replacement detection?
Transaction replacement detection is a technique used by some Bitcoin wallets to detect when a new transaction is attempting to replace an unconfirmed transaction with a higher fee rate.
How do Bitcoin transaction acceleratorservices work?
Bitcoin transaction accelerator services work by submitting the transaction to a pool of miners who have agreed to prioritize transactions submitted to the accelerator service. The service charges a fee for this service, but it can be worth it if the transaction is urgent.