StarkWare, working with Yukon Research and Eigen Labs, announced that the estimated GPU compute cost of constructing a Quantum-Safe Bitcoin (QSB) transaction has fallen to about $67, a 79% reduction from the $320 figure recorded when the first QSB transaction was included in a Bitcoin block on August 26. That first mainnet demonstration required approximately 3,100 GPU-hours.
The improvement came from the Quantum-Safe Bitcoin Optimization Challenge, launched on September 16. Developers, researchers, and AI agents competed to reduce the computational work behind the experimental method, which uses hash-based cryptography to move eligible bitcoin under Bitcoin’s existing consensus rules without requiring a protocol change. The challenge is still running, with $20,000 in prizes available for further optimizations.
According to published results, pinning-search throughput rose from about 146 million verified candidates per second to more than 820 million on an RTX 4090 GPU, while subset-selection search throughput increased from roughly 62 million to more than 620 million candidate subsets per second. A related dashboard subsequently displayed an estimate of $66 after additional leaderboard improvements, though the exact figure depends on benchmark assumptions and hardware costs.
StarkWare said: “A construction that costs a few hundred dollars per transaction is a demo. One that costs $67 is closer to something a holder with a large unexposed balance might reach for in an emergency.”
Important caveats remain. No publicly known quantum computer can currently threaten Bitcoin’s elliptic-curve signatures, and the $67 estimate has not yet been reproduced in a fresh mainnet transaction. QSB is not available as a standard wallet feature, requires compatible unspent outputs with concealed public keys, and must be sent directly to a participating miner because the transaction falls outside Bitcoin’s standard relay policy. The benchmark also excludes all-in costs such as software preparation, engineering support, network fees, and miner coordination.
Against that backdrop, Bitcoin traded near $84,000, down about 3.5% on the day, after hotter-than-expected PMI data pushed Treasury yields higher and dented risk appetite. The pullback followed a rally to roughly $87,500 after U.S. spot ETFs recorded an estimated $998.95 million in net inflows on September 21. Analysts view the $84,000–$84,400 band as a key support zone, with $86,381 and $87,400 as near-term resistance levels.
