Ordinary computers can’t run that math in reverse, but a large enough quantum computer running Shor’s algorithm, a method published in 1994 for exactly that job, could theroretically work backward from the address to the key.
That’s the real threat hanging over Satoshi-era bitcoin, whose public keys already sit onchain for anyone to copy. Last week, Google said its Willow quantum chip had produced near-perfect versions of one of the components such an attack would burn through, a step toward a machine powerful enough to try it.
Quantum computers capable of that are still likely years away (and no one has a firm timeline for when one could be built), but it’s a problem developers across the industry are rushing to solve.
One key for every swap
Zcash’s architecture gives it a problem of its own. A Zcash wallet can generate many addresses that look unrelated to each other, but they normally share one viewing key.
An attacker who…
