An open coding contest has cut the estimated cost of building a quantum-safe bitcoin transaction to about a fifth of what the first one cost in August. StarkWare said on Wednesday that one week of the Quantum-Safe Bitcoin Optimization Challenge brought the estimated GPU bill down to about $67 from roughly $320, a drop of about 79%. By Thursday morning, the contest’s live dashboard showed $66.

StarkWare runs the challenge with Yukon Research and Eigen Labs. The three launched it on Sept. 16 with $20,000 in prizes from StarkWare plus a separate Yukon prize. Entrants speed up the GPU code behind Quantum-Safe Bitcoin, or QSB, a method StarkWare’s Avihu Levy first published in April that adds hash-based protection to a bitcoin spend without changing the network’s rules. The first such transaction was mined in August after roughly 3,100 GPU-hours of work.

AI Models Hold the Records

The costly step is an offchain brute-force search for a hash that happens to be shaped like a valid bitcoin signature, so faster search code means fewer GPU-hours. On the benchmark Nvidia RTX 4090, the pinning workload climbed from 146.09 million verified candidates per second at baseline to a record of about 881 million, the dashboard shows. Subset selection now runs a little over ten times faster than at the start, StarkWare said.

Solvers landed 62 promoted submissions across the two tracks, according to StarkWare, and as of Wednesday the records belonged to developers using Opus 5 and Fable 5.1. Two GPT-6 Astra entries have since set newer pinning marks. Each entry is rerun on a CPU and checked before it counts. The format mirrors ECDSA.fail, an open leaderboard whose contributors shrank the estimated quantum cost of one step in attacking bitcoin’s signatures by 86%.

An Estimate, Not a Price

The figure covers GPU compute only, not the network fee. The August transaction paid 5,179 satoshis in fees, about $4 at the time, according to onchain data and CoinGecko prices. The dashboard models a simulated fleet of 100 RTX 3090 cards and applies measured speedups to StarkWare’s cost for each stage of the search.

“The $67 is an estimate under stated hardware assumptions, not a price, and it moves every time a solver beats the record,” StarkWare wrote. The benchmark does not build real transactions, so the gains still have to be tested against the production code.

QSB transactions also have to go straight to a miner, and they protect only coins whose public keys have not been exposed. StarkWare still favors a soft fork as the long-term fix. “This effort does not make Bitcoin quantum-safe,” the company wrote. “It makes one emergency option cheap enough to keep on the shelf.”

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