What This Tool Does

This calculator helps you estimate the probability that a blockchain attacker (e.g., a miner with some hash power) could successfully reverse a transaction after a certain number of confirmations. It's based on the original security model from the Bitcoin whitepaper by Satoshi Nakamoto.

📘 Instructions

1. Enter Attacker Hash Power (q):

   • This is the estimated share of total mining power the attacker controls.

   • Example: Enter 0.3 if the attacker controls 30% of the total network.

2. Enter Number of Confirmations (z):

   • This is how many blocks deep the transaction is.

   • Bitcoin typically recommends waiting for 6 confirmations for large transactions.

3. Click "Calculate":

   • The tool will show the probability (as a percentage) that an attacker could catch up and reverse the transaction.

✅ Example

• q = 0.3, z = 6 → The attacker has a ~1.7% chance of reversing the transaction.

• q = 0.1, z = 6 → The chance drops to almost zero.

⚠️ Notes

• A lower probability means higher transaction security.

• This tool assumes idealized conditions—real-world risks also depend on chain-specific factors and network behavior.

• Values of q must be between 0 and 1 (but not exactly 0 or 1), and z must be at least 1