StarkWare’s Quantum-Safe Bitcoin Test: $200 Cost, Block 964,199, No Fork

StarkWare researcher Avihu Levy spent a 10,000-satoshi output in a transaction confirmed inside Bitcoin block 964,199 on Wednesday, Aug. 27, using a hash-based signature scheme designed to survive an attack from a working quantum computer. The transaction required no fork and no change to Bitcoin’s consensus rules. It also cost between $150 and $200 in computation and had to be routed directly to a miner rather than broadcast through the normal mempool.

MARA Pool mined the block after receiving the transaction through its Slipstream service, a channel miners use to accept transactions outside standard relay rules. StarkWare called it the first transaction of its kind on Bitcoin mainnet.

What the Scheme Actually Does

Levy’s construction, called Quantum Safe Bitcoin (QSB), combines hash-based one-time signatures with a computational search that ties an authorization to one specific transaction. The goal is narrow: prevent forgery even if a quantum machine breaks the elliptic-curve cryptography Bitcoin currently relies on to sign transactions.

Levy first published the QSB proposal in April, estimating then that generating a single transaction would take $75 to $150 in GPU time. He described it explicitly as a last-resort spending method, not a substitute for a protocol-level upgrade. StarkWare spokesperson Nathan Jeffay told Cointelegraph the completed mainnet run took hours of computation and landed in the “low hundreds of dollars,” roughly $150 to $200.

Why the Timing Matters

The test follows a March estimate from Google researchers that a sufficiently powerful quantum computer could derive a Bitcoin private key nine to 12 minutes after the corresponding public key becomes visible on-chain. Google’s team argued that window could theoretically let an attacker swap out a pending transaction before it confirms. QSB is aimed at exactly that gap, offering spenders a way to sign a transaction that a quantum attacker cannot forge, even without a network-wide fork.

One Confirmed Report, One Corroborating Headline

Cointelegraph published the fullest account of the transaction, including the block number, the sat amount, the miner details and Jeffay’s cost figure. The Block ran a headline describing the same event as the first successfully executed quantum-resistant Bitcoin transaction and noted StarkWare’s own caveat that a protocol-level upgrade is still needed for full protection. The Block’s underlying article did not load with additional figures beyond that headline and summary, so the granular numbers here trace back to a single detailed source, with a second outlet independently confirming the core claim that the transaction happened and that StarkWare still wants a broader fix.

Nothing in either report suggests QSB is ready for ordinary wallets. The $150-to-$200 cost, the hours of computation, and the need to hand the transaction directly to a mining pool rather than the public mempool all point to a proof of concept, not a usable spending method for anyone holding a normal Bitcoin balance.

Bitcoin traded near $78,679 at the time the transaction was reported, unaffected by the announcement. The next marker to watch is whether Levy or StarkWare publish a follow-up transaction at lower cost, or whether Bitcoin Core developers respond with a concrete proposal for protocol-level quantum resistance.

Sources

• cointelegraph.com
• theblock.co