StarkWare said researcher Avihu Levy has successfully tested an experimental quantum-resistant Bitcoin transaction on mainnet. The transaction reportedly spent a 10,000-satoshi output from block 964,199 without changing Bitcoin’s consensus rules.
The company described the transaction as the first of its kind. MARA Pool mined the block after receiving the transaction directly through Slipstream because its nonstandard format prevented standard Bitcoin nodes from relaying it through the public mempool.
StarkWare spokesperson Nathan Jeffay said the transaction involved around $150 to $200 in computational costs. The company said completing the process took several hours, showing that Bitcoin outputs can be given quantum-resistant protection under the current network rules, although the method remains resource-intensive.
How StarkWare’s Quantum-Resistant Bitcoin Transaction Works
Levy introduced the Quantum-Safe Bitcoin (QSB) design in April. It combines hash-based one-time signatures with computational searches that connect authorization to a specific transaction. The system is intended to prevent unauthorized spending even if future quantum computers become capable of breaking Bitcoin’s elliptic-curve cryptography.
Google researchers estimated in March that a sufficiently powerful quantum computer could theoretically derive a Bitcoin private key within nine to 12 minutes once its public key is exposed. Google said this could potentially allow an attacker to replace a transaction before it receives enough confirmations.
Levy’s initial proposal estimated that generating a QSB transaction could require $75 to $150 in GPU computing. StarkWare’s completed mainnet demonstration placed the cost closer to $150 to $200.
QSB is designed to protect specific Bitcoin transactions rather than upgrade cryptography throughout the network. It allows coins to be transferred into outputs with additional protection without modifying the Bitcoin protocol. However, coins linked to public keys that were exposed before migration would not receive the same protection, as an attacker could potentially analyze those keys beforehand.
The transaction’s nonstandard classification under Bitcoin Core’s default relay policy creates another obstacle. Since ordinary nodes will not broadcast it before confirmation, the transaction has to be delivered directly to a cooperating miner through a service such as MARA’s Slipstream. This makes transaction preparation and direct miner access essential to the process.
StarkWare CEO Eli Ben-Sasson said QSB could act as a protective layer while the Bitcoin ecosystem develops protocol-level solutions. The test therefore demonstrates a workaround within the existing framework rather than a change to Bitcoin’s underlying cryptographic system.
Developers are also examining proposals such as BIP-360, which would introduce a Pay-to-Merkle-Root output type and remove Taproot’s quantum-vulnerable key-path spending through a proposed soft fork. Implementing such a change would require broad network coordination and activation.
QSB instead works without waiting for a protocol upgrade. The mainnet test indicates that Bitcoin’s existing consensus rules can accommodate a form of quantum-resistant spending, while more comprehensive defenses against quantum threats remain under development.
