Quantum computers are fast, but Bitcoin remains secure for now.  

1. Mining – SHA-256 has a difficulty of 2²⁵⁶, which Grover’s algorithm reduces to 2¹²⁸. Even so, classical CPUs would take 10²² years and GPUs 10¹⁷ years—far beyond the universe’s age. No real threat here.  

2. Private Keys – ECC encryption makes reversing a private key infeasible. Brute-force attacks need 2¹²⁸ operations, which even quantum computers can’t handle yet.  

Bottom line: Bitcoin is safe from quantum attacks—at least for now.