StarkWare said it executed the first quantum-resistant Bitcoin (BTC) transaction on mainnet, using a method that reaches roughly 118 bits of security against quantum attack.
Key Points:
- StarkWare says a live Bitcoin transaction was secured against quantum attack without any change to the protocol.
- The method takes hours of computation per transfer.
- Mining firm MARA processed the transaction, because ordinary nodes refuse to relay the non-standard format.
Quantum-Safe Bitcoin Transaction Reaches Mainnet
The company said the transfer moved funds that would have been vulnerable to a future quantum attack into a state where such an attack could not reach them. Avihu Levy, StarkWare's chief product officer, designed the scheme and published it in April under the name Quantum Safe Bitcoin. The result sits on the Bitcoin blockchain and is open to public inspection.
The published implementation still lacked a completed on-chain broadcast when the paper first appeared, and testing had covered only a GPU pinning phase that ran for about six hours across eight Nvidia graphics cards.
MARA mined the transaction through Slipstream, a service that accepts transfers ordinary Bitcoin nodes refuse to relay.
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Avihu Levy Method Skips Soft Fork
Standard Bitcoin transactions depend on ECDSA signatures, which a sufficiently powerful quantum computer running Shor's algorithm could break in order to derive private keys. Quantum Safe Bitcoin shifts that burden onto hash functions, which quantum machines have no known shortcut for reversing and must attack by brute force. The scheme operates within Bitcoin's legacy script limits of 201 opcodes and 10,000 bytes, and reaches roughly 118 bits of security.
Levy has described the approach as a last-resort measure rather than a replacement for ordinary payments, citing both the expense and the complexity that users would face. An average Bitcoin transaction costs about 30 cents.
The design builds on Binohash, an earlier construction from Robin Linus that added computational work to Bitcoin transactions but still leaned on cryptography quantum computers are expected to defeat. Levy's version makes a sender grind through an enormous search for a valid solution, an effort his paper puts near 70 trillion attempts. That work runs off-chain on commodity graphics cards.
Bitcoin Quantum Debate Splits Developers
Eli Ben-Sasson, StarkWare's chief executive, has argued that Bitcoin must respond to the quantum threat now rather than wait for consensus to settle around a protocol upgrade. Levy also co-authored BIP-360, a quantum-resistant address proposal merged into Bitcoin's official repository in February, which unlike this method would require a soft fork.
The April paper drew criticism alongside the praise it collected across the development community. Bitcoin analyst Daniel Batten called the quantum-safe framing an overstatement, noting that roughly 1.7 million BTC held in early pay-to-public-key addresses stay exposed no matter what new transactions do. Those holdings expose their public keys directly on the blockchain, which no method limited to new spends can undo.
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