StarkWare, the blockchain infrastructure company behind the Ethereum layer-2 network Starknet, says the first quantum-safe Bitcoin transaction has been successfully mined on the Bitcoin mainnet, offering individual holders a way to protect their funds from potential future quantum attacks without waiting for a network-wide upgrade.
What Happened
In a blog post published Wednesday, StarkWare announced the transaction used a method called Quantum-Safe Bitcoin, or QSB, developed by StarkWare researcher Avihu Levy. Levy first published the research in April. StarkWare engineer Tomer Giladi later converted the proposal into a functioning mainnet transaction.
‘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.’
Why It Matters
Bitcoin currently relies on elliptic-curve cryptography to secure transactions. A sufficiently powerful quantum computer running Shor’s algorithm could theoretically break that cryptography, deriving private keys and stealing funds. Any lasting fix would require either a hard fork, which introduces rules incompatible with older software and risks splitting the network, or a soft fork, which adds new rules while remaining compatible with older nodes.
QSB sidesteps the need for a network upgrade entirely. The method adds a second, quantum-resistant lock based on hash functions rather than elliptic curves. It uses a technique called ‘signature grinding,’ which performs computational work off-chain to find a transaction hash that Bitcoin accepts as a validly formatted signature, all within the network’s existing consensus rules.
What It Cannot Do
StarkWare acknowledged that QSB does not make Bitcoin quantum-safe as a network. It protects specific transactions that use it, nothing more. It cannot protect addresses whose public keys have already been exposed on-chain, which is the population most at risk. And transactions currently have to be sent directly to miners rather than broadcast through the standard mempool.
That last limitation sits awkwardly against the claim that holders now have a way to protect their coins. Sending a transaction straight to a miner is not something an ordinary Bitcoin holder can do, so for now this is a capability that exists rather than one most people can use.
The Bigger Picture
StarkWare CEO Eli Ben-Sasson was direct about the limits of the milestone.
‘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.
He urged the community not to treat the achievement as a reason to delay broader action, writing that he hoped the attention would help people hear the message that there is a problem, and that the way to fix it is serious soft forks for Bitcoin, which is how catastrophe can be avoided while there is still time.
Ben-Sasson has been consistent that the network-level fix remains the goal. ‘I still want Bitcoin to choose to do a soft fork and I expect we will get one,’ he said. ‘What today’s successful transaction offers Bitcoin is a reassurance that holdings can be protected before that happens.’
The urgency is not hypothetical. In June, Coinbase’s quantum advisory council estimated that roughly 7 million Bitcoin could be vulnerable due to exposed public keys and address reuse, representing a significant portion of circulating supply that could be at risk if quantum computing advances far enough.
