How does Bitcoin's SHA-256 hash algorithm ensure security, and could future advancements in computing, like quantum computers, pose a threat to its integrity?
This topic has been discussed over and over again for several years now. Just do a search for "sha-256 quantum computing" and you will see pages and pages of articles discussing your question. Here is an excerpt from one of them.
The key question is whether quantum computers can leverage their exponential search speed to break SHA-256. Grover’s algorithm provides a quadratic speedup for searching unsorted databases, reducing the required steps from O(N) to O(sqrt(N)).
For SHA-256’s hash space of 2^256 values, Grover’s algorithm could reduce the brute force search from 2^256 steps to just 2^128 steps. While a significant speedup, technical barriers prevent realizing this full quadratic advantage. The number of stable qubits available will limit problem sizes. Overhead from error correction also reduces the effective circuit depth.
Current estimates put breaking 256-bit encryption 20-30 years into the future when quantum computers may have enough stable qubits and error correction to implement Grover’s algorithm at scale. While Grover’s algorithm reduces the complexity, SHA-256’s security margin is still considered adequate against such brute force attacks.
