The work addresses a possible future threat to Bitcoin. A sufficiently powerful quantum computer could use a wallet’s exposed public key to work out its private key and steal the coins. StarkWare’s method adds a form of protection based on hashes, which are expected to withstand that attack. It fits within Bitcoin’s existing rules, so trying it did not require the network to approve an upgrade.

As such, the method is an emergency option for moving eligible coins if the quantum threat arrives before Bitcoin adopts a broader fix. Using it widely would be expensive at $320 of computing per transaction — and a lower bill could make the option more practical.

Read More: Quantum-safe bitcoin now possible without a soft fork, but costs $200 a pop, new research shows

The $66 figure remains an estimate drawn from a test of the computation. The improved code has not been shown preparing another transaction mined on Bitcoin.

Applying the speedups displayed on the contest site to its listed $320 cost breakdown yields about $83, according to CoinDesk calculations. The site says later record-setting runs go beyond those measurements, without showing which results bring its transaction estimate to $66.

Meanwhile, the method also has limits beyond cost. These transactions have to be sent directly to a miner because they do not travel through the network in the usual way, and they do not protect coins whose public keys are already exposed, which is the group a quantum attacker would reach first.