StarkWare Makes Bitcoin History With Quantum-Resistant Mainnet Transfer

• StarkWare said researcher Avihu Levy conducted an experimental quantum-resistant Bitcoin transaction on the mainnet. The transaction reportedly spent a 10,000-satoshi output in block 964,199 without requiring any changes to Bitcoin’s consensus rules.
• StarkWare called the transaction the first of its kind. MARA Pool mined the block after receiving the transaction directly through its Slipstream service, as its nonstandard structure prevented regular nodes from relaying it through the public mempool.
• StarkWare spokesperson Nathan Jeffay estimated the computational cost at roughly $150 to $200, while the company said the process took several hours. The test demonstrates that an individual Bitcoin output can be protected under the network’s existing rules, although doing so currently involves significant computational and operational expenses.

How the StarkWare Quantum Bitcoin Transaction Works

• Levy’s Quantum-Safe Bitcoin (QSB) system, initially proposed in April, combines hash-based one-time signatures with computational searches that tie transaction authorization to a specific transaction. The design aims to prevent fraudulent spending even if a powerful quantum computer eventually compromises Bitcoin’s elliptic-curve cryptography.
• In March, Google researchers estimated that a sufficiently powerful quantum computer could theoretically calculate a Bitcoin private key within nine to 12 minutes after its corresponding public key becomes exposed. Such a capability could potentially enable an attacker to replace a transaction while it is still awaiting confirmation.
• Rather than replacing Bitcoin’s cryptography across the entire network, QSB works at the individual transaction level. It enables users to transfer coins into specially protected outputs without modifying the Bitcoin protocol. However, coins with previously exposed public keys would remain vulnerable during the period before they are migrated to protected outputs.
• The transaction’s nonstandard status under Bitcoin Core’s default relay rules presents a practical limitation. Since standard nodes will not broadcast the transaction before it is confirmed, users must send it directly to a participating miner through a service such as MARA’s Slipstream. This makes advance transaction preparation and direct miner access necessary.
• StarkWare CEO Eli Ben-Sasson said QSB could serve as an interim safety measure while developers work on broader protocol-level quantum protections. The demonstration therefore represents a workaround within Bitcoin’s existing framework rather than a network-wide change to its cryptographic foundation.
• Bitcoin developers are also exploring proposals such as BIP-360, a potential soft fork that would introduce a Pay-to-Merkle-Root output type and eliminate Taproot’s vulnerable key-path spending. Unlike QSB, such a solution would require coordination across the Bitcoin network and formal activation.
• QSB does not depend on waiting for a protocol upgrade. The mainnet experiment demonstrates that Bitcoin’s current consensus rules can support a form of quantum-resistant spending, while developers continue to evaluate more comprehensive protections at the protocol level.

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