Bitcoin private keys are integers between 1 and 1077 If you were able to make a trillion guesses per second, you’d have to guess for about 3.3 decillion (1033) years to find the private key to a particular Bitcoin address. Of course it’s always possible that scientific advances, such as quantum computing, could make it feasible to crack a Bitcoin address. In this case, Bitcoin would have to hard fork to quantum-resistant cryptography. The following infographic helps to give an idea of the difficulty of brute-forcing a Bitcoin private key: