This plot shows two estimates of the time (in seconds) required for a quantum computer to break the Elliptic curve signature scheme (blue curves) as a function of time for the next 25 years. We give more and less optimistic estimates (red striped lines). Signatures in Bitcoin are made using the Elliptic Curve Digital Signature Algorithm (ECDSA) and are based on the secp256k1 curve and the discrete logarithm problem. While ECDSA digital signature is classically safe, a quantum computer with 485550 qubits can crack it within 600 seconds (red dotted horizontal line), rendering the current Bitcoin system highly insecure, as early as 2027.