StarkWare mined the first quantum-resistant Bitcoin transaction on mainnet on Aug. 26, using a hash-based method called Quantum-Safe Bitcoin that requires no change to Bitcoin's consensus rules. The technique can shield coins whose public keys stay hidden, but roughly 7 million BTC already exposed through reused addresses or visible public keys remain outside its protection.
Bitcoin infrastructure firm StarkWare says it has mined the first quantum-safe transaction on the Bitcoin mainnet, testing a way to shield funds from a future quantum computer attack without changing the network's consensus rules. The Aug. 26 transaction was included in block 964,199 after being submitted directly to Bitcoin miner MARA through its Slipstream service.
How Quantum-Safe Bitcoin works
StarkWare's method, called Quantum-Safe Bitcoin or QSB, was developed by researcher Avihu Levy, who published the research in April; StarkWare engineer Tomer Giladi then helped turn it into a working mainnet transaction. QSB moves eligible coins into a hash-based spending condition before their classical public key is revealed, shifting the security assumption away from elliptic-curve cryptography and toward the difficulty of reversing hash functions. Quantum computers can also speed up attacks on hashes, but the advantage is far smaller than the one Shor's algorithm gives against public-key cryptography.
A narrow fix, not a full defense
The protection does not extend to coins whose public keys are already visible, including older pay-to-public-key outputs, Taproot outputs, and reused addresses. The transaction is also nonstandard under default node policy, so it will not normally propagate through the public mempool — which is why StarkWare had to route it directly to MARA. StarkWare said the mainnet test cost several hundred dollars, while the project's open-source repository estimates roughly $75 to $150 for some cloud-GPU search phases. StarkWare still favors a soft fork as the long-term defense. According to X: "A quantum-safe Bitcoin tx on mainnet" proves that workable approaches exist, StarkWare CEO Eli Ben-Sasson said, while warning that the larger task is building a migration path before quantum hardware threatens exposed keys.
The 7 million BTC still exposed
Roughly 7 million Bitcoin are considered potentially vulnerable because their public keys are already visible through older address formats, Taproot usage, or address reuse, and QSB offers no rescue path for those coins. In July, BlackRock, Coinbase, Strategy, and six other institutions formed the Bitcoin Security Consortium and pledged a combined $15 million over three years toward Bitcoin security research, including post-quantum cryptography. The US Treasury has also brought digital assets into the financial sector's broader quantum-readiness planning. QSB proved a migration path exists for hidden keys — the millions of coins with exposed keys still have none.
Sources: Decrypt, CryptoSlate
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