Spiny Norman said:

A supercomputer guessing since the Big Bang still couldn’t brute-force a 256-bit key. “Just wait for quantum computers,” people say. “They’ll break AES instantly.” So let’s do the math.

Grover’s algorithm really does cut 256-bit security in half. In exponential math, though, half of 2^256 isn’t 2^255. It’s 2^128: 340 undecillion steps, still far out of reach.

In this video:
• Why “a quantum computer tries every password at once” is a myth. Measuring a superposition gives you one random key, almost always the wrong one.
• How Grover’s algorithm actually works: the keys are waves in a pool. A “lock” flips the right key’s wave, and every wave reflects about the mean. Step by step, the right key’s wave grows (hot or cold with the universe).
• Why it takes √N steps instead of N. N keys fill a square, and √N is just one side of it.
• Plugging in AES-256: √(2^256) = 2^128.
• Even at a trillion Grover steps a second, cracking ONE key takes about 1.1 × 10^19 years. That’s roughly 780 million times the age of the universe.
• Why the quantum-era advice is AES-256: halved by Grover, it still has 128-bit strength.

YT

That’s alright then.