StarkWare Executes First Quantum‑Resistant Bitcoin Spend Without a Fork

StarkWare has confirmed the first on‑chain Bitcoin transaction that resists quantum‑computer attacks, completing the test in block 964,199. The move, carried out by researcher Avihu Levy, spent a 10,000‑satoshi output that was protected by Levy’s Quantum Safe Bitcoin (QSB) scheme. The block was mined by MARA Pool after the transaction was forwarded to them through MARA’s Slipstream service.

QSB marries hash‑based one‑time signatures with a computational search that ties the authorization to the exact transaction. The design is meant to thwart forgery even if a quantum machine breaks Bitcoin’s elliptic‑curve cryptography. By demonstrating the transaction on the mainnet, StarkWare has shown that Bitcoin’s existing consensus rules can accommodate a quantum‑resistant spending method without requiring a protocol change.

The test was expensive, with StarkWare estimating the GPU‑compute cost at roughly $150–$200, a figure that matches Levy’s earlier estimate of $75–$150 for generating a QSB transaction. Google researchers in March had warned that a powerful quantum computer could derive a Bitcoin private key within 9–12 minutes after the public key appears, potentially allowing an attacker to replace a pending transaction.

Because QSB transactions are classified as non‑standard under Bitcoin Core’s default relay rules, they are not propagated by ordinary nodes. As a result, the transaction had to be submitted directly via Slipstream. Levy and StarkWare view QSB as a stop‑gap safety net while the community works on broader protocol upgrades, such as the proposed BIP‑360 soft fork that would replace Taproot’s quantum‑vulnerable key‑path spend with a Pay‑to‑Merkle‑Root output type.