- First quantum-safe Bitcoin transaction mined on Bitcoin mainnet.
- Method uses hash-based security without changing Bitcoin’s consensus rules.
- StarkWare still favors soft fork as long-term quantum defense.
Starkware, the blockchain infrastructure company behind Ethereum layer-2 network Starknet, announced Wednesday that the first quantum-safe Bitcoin transaction has been mined on Bitcoin mainnet. The transaction tests protecting funds from future quantum attacks without changing the network’s consensus rules.
In a blog post, the company said the transaction used Quantum-Safe Bitcoin, or QSB, a method developed by researcher Avihu Levy and turned into a working mainnet transaction by engineer Tomer Giladi.
“A quantum-safe transaction was mined on the Bitcoin mainnet today that holds up against an adversary running a working quantum computer,” Starkware wrote. “Bitcoin holders now have a way to move coins into storage a quantum computer cannot open.”
Bitcoin uses elliptic-curve cryptography, which a sufficiently powerful quantum computer running Shor’s algorithm could theoretically break. Protecting the network could eventually require a hard fork or a soft fork.
However, Starkware said a soft fork remains the preferred long-term solution, while QSB protects individual holdings without waiting for a network upgrade. “I still want Bitcoin to choose to do a soft fork and I expect we will get one,” CEO Eli Ben-Sasson said.
Meanwhile, researchers are assessing which Bitcoin holdings could be most exposed to quantum attacks. In June, Coinbase‘s quantum advisory council estimated roughly 7 million Bitcoin could be vulnerable because of exposed public keys and address reuse.
QSB adds a second, quantum-resistant lock based on hash functions rather than elliptic curves. It uses “signature grinding,” performing computational work off-chain to find a transaction hash Bitcoin will accept as validly formatted signature.
Consequently, Starkware acknowledged QSB does not make Bitcoin quantum-safe overall. It cannot protect addresses with already-exposed public keys and currently requires transactions to be sent directly to miners.
“This amazing feat should not be viewed as a message saying ‘Bitcoin is prepared for the quantum threat.’ Far from it,” Ben-Sasson wrote on X.
“I hope whatever attention this brilliant work gets will also help folks hear loud and clear our message: Huston, we’ve got a problem, and the way to fix it should be to get serious about serious soft forks for [Bitcoin],” he said. “That’s how catastrophe can be avoided, and we still have time.”
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