Quantum-safe bitcoin transactions get cheaper after AI-assisted coding contest: estimated cost falls to $66

Preparing a quantum-resistant bitcoin transaction now costs an estimated $66 in computing, down from about $320 at the start of September, according to research firm StarkWare.

The starting point was a real transaction. In August, StarkWare built a bitcoin payment protected by a post-quantum scheme and mined it on the network. The work consumed roughly 3,100 hours of GPU time spread across around 100 graphics cards, and the company put the resulting bill at about $320. That figure covers only the off-chain computation; it excludes the standard bitcoin fee.

StarkWare then published the code and invited outsiders to make it faster. Over a week, contestants — many of them using AI coding assistants — rewrote the search routine that hunts for valid solutions. The competition's leaderboard shows the top entry testing about 881 million candidate solutions per second, up from roughly 146 million for the original implementation on the same reference GPU. Roughly six times the throughput means proportionally less hardware time and a much smaller invoice.

Cost aside, the technique targets a specific weakness in bitcoin as it exists today. A quantum computer powerful enough could derive a wallet's private key from its public key and drain it. The company's approach relies on hash-based signatures, a family of cryptography believed to resist that kind of attack. Because it works within bitcoin's current consensus rules, no soft fork or community approval was needed to demonstrate it — anyone holding suitable coins could use it now.

That makes it a contingency plan rather than a proposal for everyday payments: a way to move vulnerable coins if a quantum-capable machine appears before bitcoin ships a native fix. At $320 per transaction, mass adoption of the workaround would be costly; at $66, it starts to look usable for holders who need it.

Some caveats attach to the new number. The $66 comes from extrapolation, not from a second mined transaction — the optimized code has not yet produced one on bitcoin. CoinDesk, running the contest site's published speedups against its own $320 cost breakdown, arrived at roughly $83 instead. The site notes that later record runs exceeded the measured benchmarks but does not identify which results underpin the $66 figure.

The approach also has structural limits. Quantum-protected transactions cannot propagate through the peer-to-peer network in the normal fashion, so each one must be delivered straight to a miner. And the scheme only helps coins whose public keys remain hidden — coins that have already revealed their keys are precisely the ones a quantum attacker would target first, and this method offers them no protection.